Nadia Morin-Crini

Eric Lichtfouse

Guorui Liu
email: grliu@rcees.ac.cn

Vysetti Balaram

Ana Rita
email: ritalado@fe.up.pt

Lado Ribeiro

Zhijiang Lu
email: zhijianglu@zju.edu.cn

Friederike Stock
email: stock@bafg.de

Margarida Eric Carmona

Ribau Teixeira

Lorenzo

Lorenzo A Picos-Corrales

Juan Carlos Moreno-Piraján

Liliana Giraldo
email: lgiraldogu@unal.edu.co

Cui Li

Abhishek Pandey

Didier Hocquet
email: dhocquet@chu-besancon.fr

Giangiacomo Torri
email: torri@ronzoni.it

Grégorio Crini
email: gregorio.crini@univ-fcomte.fr

A R L Ribeiro

M R Teixeira

J C Moreno-Piraján

Emerging contaminants: analysis, aquatic compartments and water pollution

Keywords: Emerging contaminants, Substances of global concern, Pharmaceuticals, Personal care products, Pesticides, Alkylphenols, Persistent organic pollutants, Microplastics, Rare earth elements, Nanoparticles, Biological agents, Analysis, Water pollution, Aquatic compartments

la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Although water quality problems are largely associated with developing countries, they also persist in developed countries and include, for example, the loss of pristine water bodies, impacts related to changes in hydromorphology, the spread of invasive species, the loss of biodiversity, and the increasing occurrence of chemical substances [START_REF] Priac | Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination[END_REF]. The water quality problems are intimately linked to human activities, whether domestic, agricultural or industrial. Indeed, population growth, agricultural intensification, rapid urbanization, increased industrial production and climate change are beginning to impact on Nature's ability to provide safe and clean water for our essential uses and functions. One of the most important global environmental problems is water pollution by chemicals [START_REF] Aristizabal-Ciro | Monitoring pharmaceuticals and personal care products in reservoir water used for drinking water supply[END_REF][START_REF] Hernández-Padilla | Assessing wastewater treatment in Latin America and the Caribbean: enhancing life cycle assessment interpretation by regionalization and impact assessment sensibility[END_REF]Morin-Crini and Crini Table 1. 1 (continued) General topic movement in the global environment. Indeed, the issue of contaminants/pollutants and their impact on the environment (especially on water quality), society and human health is common to the entire World, making it a global concern at the present time. However, concentration levels are extremely variable from one continent to another, from one country to another and even from one region to another. Recently, [START_REF] Fekadu | Pharmaceuticals in freshwater aquatic environments: a comparison of the African and European challenge[END_REF], comparing levels of contamination of pharmaceuticals such as carbamazepine and sulfamethoxazole in surface waters between Africa and Europe, observed that the maximum concentrations reported in Africa were 20,000 times higher than in Europe. The authors indicated that the variation in the consumption of pharmaceuticals, the partial removal of substances in wastewater treatment plants and the direct discharge of wastewater from livestock farms are among the reasons that may explain the observed differences [START_REF] Fekadu | Pharmaceuticals in freshwater aquatic environments: a comparison of the African and European challenge[END_REF]. Other studies showed a correlation between the presence of emerging substances in the aquatic environment and discharges from wastewater treatment plants [START_REF] Stackelberg | Efficiency of conventional drinking-water-treatment processes in removal of pharmaceuticals and other organic compounds[END_REF][START_REF] Kasprzyk-Hordern | The occurrence of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs in surface water in South Wales, UK[END_REF][START_REF] Watkinson | The occurrence of antibiotics in an urban watershed: from wastewater to drinking water[END_REF][START_REF] Ort | Sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in wastewater systems: are your conclusions valid? A critical review[END_REF][START_REF] Basile | Review of endocrine-disrupting-compound removal technologies in water and wastewater treatment plants: an EU perspective[END_REF][START_REF] Gonzalez | Presence and biological effects of emerging contaminants in Llobregat River basin: a review[END_REF][START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF][START_REF] Priac | Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination[END_REF][START_REF] Gilabert-Alarcón | Regulatory challenges for the use of reclaimed water in Mexico: a case study in Baja California[END_REF][START_REF] Mezzelani | Pharmaceuticals in the aquatic environments: evidence of emerged threat and future challenges for marine organisms[END_REF].

The vast majority of the anthropogenic substances are currently not regulated and some have been regulated only recently, namely certain pesticides and alkylphenols known as endocrine disruptors or endocrine-disrupting chemicals [START_REF] Daughton | Non-regulated water contaminants: emerging research[END_REF]Lu and Gan 2014a;[START_REF] Gee | Considerations of endocrine disruptors in drinking water (chapter 18)[END_REF][START_REF] Petrie | A review on emerging contaminants in wastewaters and the environment: current knowledge, understudied areas and recommendations for future monitoring[END_REF][START_REF] Barbosa | Occurrence and removal of organic micropollutants: an overview of the watch list of EU Decision 2015/495[END_REF][START_REF] Priac | Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination[END_REF][START_REF] Jurado | Occurrence, fate and environmental risk assessment of the organic microcontaminants included in the watch lists set by EU decisions 2015/495 and 2018/840 in the groundwater of Spain[END_REF][START_REF] Sousa | Monitoring of the 17 EU Watch List contaminants of emerging concern in the Ave and the Sousa Rivers[END_REF]. For example, paraquat, an herbicide used worldwide since the 1960s that caused severe and fatal poisonings, was banned in the European Union in 2003 and withdrawn from the market in 2007. Another example is the organochlorine insecticide Table 1. 1 (continued) General topic chlordecone, introduced in 1958 and banned in 1978 in the US and in the early 1993 in the French West Indies [START_REF] Rana | Cyclodextrin as a complexation agent in the removal of chlordecone from water[END_REF]. In 2000, a first list of 33 priority substances (several pesticides, the phthalate di(2-ethylhexyl)-phthalate, octylphenol, nonylphenol, solvents, among others) was established as a control measure for the next 15 years based on their significant risk to or via the aquatic environment (European Water Framework Directive 2000/60/EC; Decision 2455/2001/EC). In 2008, the Directive 2008/105/EC layed down the environmental quality standards (EQS) for the priority substances and certain other pollutants. Moreover, other groups of substances were also targeted to be reviewed for possible future prioritization (e.g., bisphenol A, musk xylene, perfluorooctane sulphonic acid, dioxins, polychlorinated biphenyls), and in fact some of them were later included in the list of priority substances by Directive 2013/39/EU, which enlisted 45 priority subtances or group of substances. Additionally, this Directive preconized the launch of the first Watch List and recommended to include diclofenac, 17-β-estradiol and 17-α-ethinylestradiol. The non-steroidal anti-inflammatory drug diclofenac is often detected in European municipal wastewater treatment plants influents and effluents, surface water and groundwater. The first complete European watch list of substances of emerging concern (European Decision 2015/495/EU of 20 March 2015) was launched in 2015 and included three hormones (17-α-ethinylestradiol, 17-β-estradiol and estrone), four pharmaceuticals (diclofenac, azithromycin, clarithromycin and erythromycin), eight pesticides (methiocarb, oxadiazon, imidacloprid, thiacloprid, thiamethoxam, clothianidin, acetamiprid and triallate), a UV filter (2-ethylhexyl-4methoxycinnamate) and an antioxidant (2,6-di-tert-butyl-4-methylphenol) commonly used as food additive [START_REF] Priac | Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination[END_REF]. This list is dynamic and the latest update was published in 2018 (e.g., with the European Decision 2018/840/ EU), by removing tri-allate, oxadiazon, 2,6-di-tert-butyl-4-methylphenol and diclofenac (due to the sufficient high-quality monitoring data already available, according to the Decision), as well as 2-ethylhexyl-4-methoxycinnamate (since data is needed for sediment rather than water), and by adding 3 candidates: the insecticide metaflumizone, and the antibiotics amoxicillin and ciprofloxacin. Recently, the substances propiconazole and 4-nonylphenol were banned in Europe in November 2018 and July 2019, respectively. Indeed, from a regulatory point of view, the situation is constantly evolving [START_REF] Barbosa | Occurrence and removal of organic micropollutants: an overview of the watch list of EU Decision 2015/495[END_REF][START_REF] Jurado | Occurrence, fate and environmental risk assessment of the organic microcontaminants included in the watch lists set by EU decisions 2015/495 and 2018/840 in the groundwater of Spain[END_REF][START_REF] Sousa | Monitoring of the 17 EU Watch List contaminants of emerging concern in the Ave and the Sousa Rivers[END_REF]. The chronicle of European science, policy and legislation to develop a groundwater monitoring list can be found in the review by [START_REF] Lapworth | Developing a groundwater watch list for substance of emerging concern: a European perspective[END_REF]. Water contamination by pesticides, pharmaceuticals and industrial chemicals has become a global environmental and health crisis (Morin- Crini and Crini 2017;[START_REF] Crini | Wastewater treatment: an overview (Chapter 1)[END_REF][START_REF] Patel | Pharmaceuticals of emerging concern in aquatic systems: chemistry, occurrence, effects, and removal methods[END_REF][START_REF] Tolboom | Algal-based removal strategies for hazardous contaminants from the environment -a review[END_REF]. There is also a mobilization of the global scientific community on all subjects concerning emerging substances, from their analysis to their removal, their behavior in the environment and their impact on health (Table 1. 1).

The objective of this chapter is to present a recent state of knowledge on emerging substances, considering several aspects presented in three parts. After general considerations on emerging contaminants, the first part is devoted to analysis and detection of emerging substances with the presentation of chromatographic methods coupled to mass spectrometry for their analysis and detection. The detection of microplastics in water and sediments is also discussed. The second part of this chapter presents the occurrence, fate and toxicity of alkylphenols, rare earth elements and nanoparticles in the aquatic environment. The third part presents selected examples of contamination described from around the world, from China to Portugal, and Latin America.

General Considerations on Emerging Contaminants

Contamination and Pollution

Contamination/Pollution arises from all sectors of human activity, and is due to natural (petroleum, minerals, etc.) and anthropogenic causes (e.g., sewage treatment sludge or persistent organic pollutants produced by waste incineration) and especially to synthetic substances produced by chemical industries (e.g., dyes, fertilizers, pesticides, and so on). The terms contamination/pollution and contaminant/ pollutant are often used in relation to subjects like environment, food and medicine (Crini andBadot 2007, 2010;[START_REF] Priac | Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination[END_REF]. Both contaminant and pollutant refer to undesirable or unwanted substances. Pollutant refers to a harmful substance but contaminant is not necessarily harmful since contamination refers simply to the presence of a chemical substance where it should not be. This means that all pollutants are contaminants, but not all contaminants are pollutants. In this chapter, both these terms were used.

What Is an Emerging Contaminant?

A chemical pollutant is a substance toxic for flora, fauna and for humans, and present at concentrations such that, in Nature, has repercussions for the environment and/or on health in general (Crini andBadot 2007, 2010;[START_REF] Sauvé | A review of what is an emerging contaminant[END_REF][START_REF] Harmon | (ed) Persistent organic pollutants (POPs): analytical techniques, environmental fate and biological effects[END_REF]. Examples of pollutants/micropollutants known to the public are various, including nitrates, phosphates, pesticides such as glyphosate or atrazine, detergents (cleaning products), metals, dyes, pharmaceuticals such as diclofenac or ibuprofen, licit drugs (caffeine 1,3,7-trimethyl-3-7-dihydro-1H-purine-2,6-dione), illicit drugs (cocaine, amphetamines), synthetic (17-α-ethinylestradiol) and natural (17-β-estradiol) hormones, cosmetics and personal care products (parabens, triclosan, sunscreens and UV filters, domestic biocides, disinfectants), food derivatives and additives (nitrites, caffeine, artificial sweeteners), food packaging and containers (phthalates, other plasticizers), industrial substances (bisphenol A, surfactants, chlorinated solvents such as trichloroethylene, disinfection products, biocides, lubricants, silicones, substances used in nonstick materials, ingredients used in paints), microbial pathogens, indoor pollutants, etc. Other substances, that are less known by the public, are considered substances of concern: estrogens (estriol), pesticides less known by the public but widely used such as methiocarb, triallate and oxadiazon, neonicotinoids (insecticides), 2,6-di-tert-butyl-4-methylphenol (anti-oxidant), UV filter (2-ethylhe xyl-4-methoxycinnamate), macrolide antibiotics used in veterinary medicine and aquaculture, volatile organic compounds, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, bromine-containing flame-retardants, perfluorinated compounds and perfluorinated alkyl substances, polybrominated diphenyl ethers, alkylphenols and alkylphenol polyethoxylates, rare earth elements, radionuclides, metalloids such as selenium, and many more [START_REF] Kolpin | Pharmaceuticals, hormones, and other organic wastewater contaminants in US streams, 1999-2000: a national reconnaissance[END_REF][START_REF] Daughton | Non-regulated water contaminants: emerging research[END_REF][START_REF] Tijani | Pharmaceuticals, endocrine disruptors, personal care products, nanomaterials and perfluorinated pollutants: a review[END_REF]). The public is also increasingly aware of so-called emerging substances: antibiotics, analgesics, hormones and other drugs (anti-inflammatory, antidiabetic, antiepileptic), nanoparticles, bioterrorism and sabotage agents, and pathogens (cyanotoxins or algal toxins, mycotoxins, antibiotic-resistant organisms, etc.). The list of emerging substances and products is therefore particularly long [START_REF] Tijani | Pharmaceuticals, endocrine disruptors, personal care products, nanomaterials and perfluorinated pollutants: a review[END_REF] and is also of great interest to the scientific community (Table 1.1).

The term "emerging contaminants/pollutants" refers primarily to those for which there are currently no regulations requiring monitoring or public reporting of their presence in our water supply or wastewaters. The US Environmental Protection Agency (EPA) defines an emerging pollutant as "a chemical or material which because of a recent source that it originates, or because of a new pathway that has developed, and for which a lack of published health standards exist poses a perceived, potential, or real threat to the human health or the environment" (source: US EPA 2012, Washington, DC). Their occurrence results from point (urban and industry) or diffuse (agriculture) contamination/pollution sources. Various other terms and definitions can be found in the literature. Indeed, there is no generally accepted definition, each definition and interpretation depending on the respective perspective and/or objective [START_REF] Priac | Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination[END_REF][START_REF] Salthammer | Emerging indoor pollutants[END_REF]. In Europe, the term contaminant of emerging concern is a common term for chemicals that are currently not regulated (not submitted to a routine monitoring and/or emission control regime) but may be under scrutiny for future regulation [START_REF] Dulio | Emerging pollutants in the EU: 10 years of NORMAN in support of environmental policies and regulations[END_REF]).

In the bibliography, there are several terms to denote emerging contaminants almost interchangeably such as emerging organic contaminants, emerging substances, substances of emerging concern, contaminants of emerging concern, emerging pollutants, emerging micropollutants and other similar terminologies (trace organic contaminants, micropollutants, trace organic compounds, trace pollutants, constituents of emerging concern, xenobiotic organic compounds, etc.). However, it is important to point out that all emerging pollutants are emerging contaminants, but not all emerging contaminants are emerging pollutants. This is often confuse in the literature. There are also terms that refer to subsets of emerging substances. All of these terms refer to many different types of chemicals, such as pharmaceuticals and drugs (medicines, non-prescription drugs, endocrine disrupting compounds), personal care products and cosmetics (soaps, fragrances, bisphenols, parabens, triclosan, endocrine disrupting compounds), household cleaning products, industrial compounds (surfactants, flame/fire retardants, monomers and polymers, solvents), pesticides (new formulations), and other agricultural products (fertilizers, lawn care products) and biocides [START_REF] Tijani | Pharmaceuticals, endocrine disruptors, personal care products, nanomaterials and perfluorinated pollutants: a review[END_REF][START_REF] Priac | Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination[END_REF][START_REF] Patel | Pharmaceuticals of emerging concern in aquatic systems: chemistry, occurrence, effects, and removal methods[END_REF]. Endocrine disruptors can be found in the pharmaceutical and/or cosmetic category. They also include a range of other compounds, including pesticides and phytocompounds, as well as industrial chemicals. Many researchers consider endocrine disruptors to be a narrower subclass of emerging substances. This term refers to specific substances that have been shown to have an effect on the endocrine system of aquatic organisms or that have been designed to act on the human hormone system. Other substances, products and new technologies of concern include UV filters, corrosion inhibitors (benzothiazoles), 3D-printing (thermoplastics, additives), E-cigarettes and E-shishas, nanomaterials and nanoparticles (new products of new anthropogenic processes, nanosprays), microplastics and nanoplastics (considered as truly "new" to the environment). Biological agents and other pathogens (pathogenic bacteria, multi-drug resistant microbes) can also be defined as emerging [START_REF] Priac | Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination[END_REF][START_REF] Crini | Wastewater treatment: an overview (Chapter 1)[END_REF][START_REF] García | A review of emerging organic contaminants (EOCs), antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs) in the environment: increasing removal with wetlands and reducing environmental impacts[END_REF]. Indeed, the literature also includes discussion of antibioticresistant microorganisms and antibiotic-resistance genes under the broad category of emerging contaminants. More recently, nanoparticles have also been included in the class of emerging substances [START_REF] Mearns | Effects of pollution on marine organisms[END_REF][START_REF] Zhao | Emerging pollutants -part I: occurrence, fate and transport[END_REF][START_REF] Marchi | Engineered nanomaterials: from their properties and applications, to their toxicity towards marine bivalves in a changing environment[END_REF][START_REF] Matich | Applications of metabolomics in assessing ecological effects of emerging contaminants and pollutants on plants[END_REF]. [START_REF] Luo | A review on the occurrence of micropollutants in the aquatic environment and their fate and removal during wastewater treatment[END_REF] proposed to classify emerging contaminants in five categories, namely personal care products (fragrances, disinfectants, UV filters and insect repellents), pharmaceuticals (non-steroidal anti-inflammatory drugs, antibiotics, lipid regulator, anticonvulsants, β-blockers), steroid hormones, industrial chemicals (plasticizers, fire retardants, bisphenol A, phthalates) and surfactants (cleaning products, alkylphenols), excluding pesticides. According to Norman network (2016), over 1000 emerging chemicals are recognized and classified in four main groups, i.e., drugs, personal care products, endocrine disruptors and pesticides (Norman network 2016; [START_REF] Dulio | Emerging pollutants in the EU: 10 years of NORMAN in support of environmental policies and regulations[END_REF]. Another simplified classification for pharmaceuticals and personal care products proposed by [START_REF] Ebele | Pharmaceuticals and personal care products (PPCPs) in the freswater aquatic environment[END_REF] considers only one main family of endocrine disruptors, which is subdivided into three categories: (1) personal care products including cosmetics, disinfectants, conservation agents, fragrances and UV screens; (2) nonsteroidal drugs, including antibiotics, analgesics, and other pharmaceuticals (human and veterinary drugs); and (3) steroids (estrogens, etc.). [START_REF] Patel | Emerging pollutants in aquatic environment: source, effect, and challenges in biomonitoring and bioremediation -a review[END_REF] recently proposed four groups of emerging contaminants (excluding pesticides), i.e., pharmaceuticals, endocrine disruptors (including cosmetics, hormones, xenobiotics, plastics), personal care products (including cosmetics, UV filters, disinfectants, insect repellents such as triclosan, synthetic hormones, lipid regulators and steroids), and perfluorinated compounds. Other researchers and organizations have classified emerging substances into three broad categories: pharmaceuticals, personal care products and endocrine disrupting compounds, excluding pesticides. However, these classifications can be confusing because some personal care products are also endocrine-disrupting chemicals while other drugs are not (Darbre 2015; [START_REF] Gee | Considerations of endocrine disruptors in drinking water (chapter 18)[END_REF]. In reality, there is not yet an internationally recognized general classification for emerging substances. Nevertheless, many researchers agree with the definition given by the US EPA [START_REF] Gogoi | Occurrence and fate of emerging contaminants in water environment: a review[END_REF]. Figure 1.1 provides a general classification of emerging contaminants and issues of concern in water compartments into seven categories, regardless of their risk to health or the environment.

Examples of Emerging Contaminants of Recent Concern

Polyfluoroalkyl or perfluoroalkyl, known by the abbreviation PFASs, are a family of emerging contaminants that have recently become a concern [START_REF] Melzer | Association between serum perfluorooctanoic acid (PFOA) and thyroid disease in the U.S. national health and nutrition examination survey[END_REF][START_REF] Gallo | Serum perfluooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) concentrations and liver function biomarkers in a population with elevated PFOA exposure[END_REF]; [START_REF] Barry | Perfluorooctanoic acid (PFOA) exposures and incident cancers among adults living near a chemical plant[END_REF][START_REF] Vestergren | Human dietary exposure to per-and poly-fluoroalkyl substances (PFASs) (chapter 12)[END_REF]DeWitt 2015;[START_REF] Xiao | Emerging poly-and perfluoroalkyl substances in the aquatic environment: a review of current literature[END_REF][START_REF] Dong | Review: micro-organic contaminants in groundwater in China[END_REF][START_REF] Lorenzo | Analytical challenges to determine emerging persistent organic pollutants in aquatic ecosystems[END_REF][START_REF] Brusseau | Subsurface pollution (Chapter 15)[END_REF][START_REF] Ng | Fate of environmental pollutants[END_REF][START_REF] Klemes | Reduction of a tetrafluoroterephthalonitrile-β-cyclodextrin polymer to remove anionic micropollutants and perfluorinated alkyl substances from water[END_REF][START_REF] Pan | Analysis of emerging per-and polyfluoroalkyl substances: progress and current issues[END_REF][START_REF] Salthammer | Emerging indoor pollutants[END_REF]. Perfluoroalkyl substances is a term used for a family of highly fluorinated chemicals (the term perfluorinated compounds can also be found in the literature). These substances contain fluorinated molecular chains that degrade very slowly in the environment and have a high bioaccumulation potential. They include subclasses such as perfluoroalkyl sulphonic acids (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs). The list is particularly long as the Chemical Abstracts Service registers more than 4000 compounds. These synthetic substances have been produced and widely used since the 1950s before their harmful health effects and persistence came to light. Today, they are still widely used in consumer products and for industrial uses, finding targeted applications in a wide variety of fields. For example, perfluoroalkyl substances (perfluoroalkyl sulfonates and perfluoroalkyl carboxylates) are widely used as polymer constituents in food containers and packaging (fast-food packaging, pizza boxes), processing aids in non-stick cookware (Teflon ® ), surface-active agents in waterproof clothing and stain-resistant carper (stain-resistant textiles, water-resistant textiles), and cleaning products. They are also used as individual ingredients in firefighting foams used in many military installations and airports, and in painting materials [START_REF] Xiao | Mechanisms for removal of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) from drinking water by conventional and enhanced coagulation[END_REF]DeWitt 2015;[START_REF] Brusseau | Subsurface pollution (Chapter 15)[END_REF][START_REF] Pan | Analysis of emerging per-and polyfluoroalkyl substances: progress and current issues[END_REF]. Other applications include coatings and metal plating, hydraulic fluids, medical devices, cosmetics (shampoos), pesticides, and photo imaging. The best known are perfluorooctanoic acid (PFOA) used as a repellent coating for textiles, paper products and cookware and perfluorooctanesulfonic acid (PFOS) used in fire fighting foams, carpet treatments, and mist suppressants in metal plating operations.

In 2009, perfluoroalkyl substances were listed in Annex B of the Stockholm Convention on Persistent Organic Pollutants (Stockholm Convention 2009: CN524-TREATIES 4, UNEP, Geneva) as substances of concern, restricted but not completely banned. Many substances are currently being considered for restriction under the 2015 Rome Directive (Stockholm Convention 2015: Decision POPRC-11/4, UNEP, Rome) and will be banned under the EU Chemicals Regulation from 2020. Indeed, perfluoroalkyl substances are chemicals considered to be persistent organic pollutants and long-range transported anthropic contaminants found at high concentrations in human and wildlife populations around the World, including in Arctic marine mammals. Their ubiquous persistence in the environment and their toxicity in animal models raise concerns about the effects on human health of chronic low-level exposure [START_REF] Melzer | Association between serum perfluorooctanoic acid (PFOA) and thyroid disease in the U.S. national health and nutrition examination survey[END_REF]DeWitt 2015;[START_REF] Pan | Analysis of emerging per-and polyfluoroalkyl substances: progress and current issues[END_REF]). Perfluoroalkyl substances have been linked to cancer, liver damage and thyroid disease [START_REF] Melzer | Association between serum perfluorooctanoic acid (PFOA) and thyroid disease in the U.S. national health and nutrition examination survey[END_REF][START_REF] Gallo | Serum perfluooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) concentrations and liver function biomarkers in a population with elevated PFOA exposure[END_REF][START_REF] Barry | Perfluorooctanoic acid (PFOA) exposures and incident cancers among adults living near a chemical plant[END_REF][START_REF] Vestergren | Human dietary exposure to per-and poly-fluoroalkyl substances (PFASs) (chapter 12)[END_REF]. [START_REF] Klemes | Reduction of a tetrafluoroterephthalonitrile-β-cyclodextrin polymer to remove anionic micropollutants and perfluorinated alkyl substances from water[END_REF] recently reported that more than 16 million people in the United States were exposed to drinking water with perfluorinated alkyl substances concentrations exceeding 10 ng/L. [START_REF] Melzer | Association between serum perfluorooctanoic acid (PFOA) and thyroid disease in the U.S. national health and nutrition examination survey[END_REF] previously reported that higher concentrations of serum perfluorooctanoate and perfluorooctane sulfonate are associated with current thyroid disease in the general adult population in the United States. [START_REF] Gallo | Serum perfluooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) concentrations and liver function biomarkers in a population with elevated PFOA exposure[END_REF] demonstrated an association between concentrations of perfluorooctanoate and perfluorooctane sulfonate and serum levels of alanine of transaminase, a marker of hepatocellular damage. In another study, [START_REF] Barry | Perfluorooctanoic acid (PFOA) exposures and incident cancers among adults living near a chemical plant[END_REF] reported that exposure to perfluorooctanoic acid is associated with renal, pancreatic and testicular cancer in rats. Other examples can be found in the review by [START_REF] Vestergren | Human dietary exposure to per-and poly-fluoroalkyl substances (PFASs) (chapter 12)[END_REF].

The presence of perfluoroalkyl substances in tap water has become a priority. However, due to their chemical stability and composition, these substances are poorly or even not eliminated by conventional water treatment methods. Because they have no carbon-carbon double bonds and no functional groups, they are also resistant to advanced oxidation processes. Innovation is therefore required to find removal solutions.

Another topical issue concerns plastics/microplastics [START_REF] Wagner | Microplastics in freshwater ecosystems: what we know and what we need to know[END_REF][START_REF] Avio | Plastics and microplastics in the oceans: from emerging pollutants to emerged threat[END_REF][START_REF] Lambert | Microplastics are contaminants of emerging concern in freshwater environments: an overview[END_REF][START_REF] Peeken | Arctic Sea ice is an important temporal sink and means of transport for microplastic[END_REF]. Plastics are synthetic polymers composed of different materials that range from cellulose to crude oil and are used in a broad ever-growing spectrum of applications. They are separated into thermoplastics and thermosets and consist of different synthetic polymers of which polypropylene, polyethylene, polyvinyl-chloride, polyurethane, polyethylene terephthalate and polystyrene were the most commercially demanded in 2017 (Plastics Europe 2017). Moreover, tire wear may be included in a larger definition of microplastics (Wagner et al. 2018) (although ISO does not cover it; ISO 2013). Plastics are important materials that are abundant in our economy (because they are lighter and cheaper than other materials) and are part of our daily lives, making our lives easier in many ways. Since the 1950s, the plastic production rose exponentially to 359 million tons in 2018 (Plastics Europe 2019). However, if they are not properly disposed of or recycled after use, they are often released into the environment where they can persist for long periods of time and break down into smaller and smaller pieces, called microplastics, which are of concern [START_REF] Lambert | Microplastics are contaminants of emerging concern in freshwater environments: an overview[END_REF]. Figure 1.2 shows accumulation of plastic debris on a shoreline in France.

Microplastics are indeed widespread contaminants worldwide, from the Arctic to the Antarctic [START_REF] Peeken | Arctic Sea ice is an important temporal sink and means of transport for microplastic[END_REF]) via tropical islands [START_REF] Imhof | Spatial and temporal variation of macro-, meso-and microplastic abundance on a remote coral island of the Maldives, Indian Ocean[END_REF], present not only in all the aquatic compartments (rivers, sediments, marine environment), but also in soils and in the atmosphere [START_REF] Avio | Plastics and microplastics in the oceans: from emerging pollutants to emerged threat[END_REF][START_REF] Prata | Methods for sampling and detection of microplastics in water and sediment: a critical review[END_REF][START_REF] Möller | Finding microplastics in soils: a review of analytical methods[END_REF][START_REF] Xu | Microplastics in aquatic environments: occurrence, accumulation, and biological effects[END_REF]). In fact, plastics have also been detected in remote mountain lakes and deep-sea sediments [START_REF] Cauwenberghe | Microplastic pollution in deep-sea sediments[END_REF][START_REF] Free | High-levels of microplastic pollution in a large, remote, mountain lake[END_REF], and even in the air we breathe [START_REF] Gasperi | Microplastics in air: are we breathing it in?[END_REF][START_REF] Allen | Atmospheric transport and deposition of microplastics in a remote mountain catchment[END_REF]. They are considered as emerging contaminants. However, the first studies on the description of polystyrene spherules and pieces in the environment and their effects date back to the 1970s with the works of Carpenter and co-workers (Carpenter et al. 1972;[START_REF] Carpenter | Plastics on the Sargasso Sea surface[END_REF]. Microplastics were already identified as persistent in the environment and as potentially to accumulate in different marine ecosystems.

Special attention is paid to plastic pollution of the marine environment. Indeed, this issue is a growing environmental concern worldwide, as shown by the recent explosion of literature on their identification, quantification and behavior (e.g., [START_REF] Avio | Plastics and microplastics in the oceans: from emerging pollutants to emerged threat[END_REF][START_REF] Juliano | Cosmetic ingredients as emerging pollutants of environmental and health concern. A mini-review[END_REF][START_REF] Barboza | Marine microplastic debris: an emerging issue for food security, food safety and human health[END_REF]Lin et al. 2018b;[START_REF] Da Costa | Micro(nano)plasticsanalytical challenges towards risk evaluation[END_REF][START_REF] Mishra | Marine microfiber pollution: a review on present status and future challenges[END_REF][START_REF] Ng | Fate of environmental pollutants[END_REF][START_REF] Prata | Methods for sampling and detection of microplastics in water and sediment: a critical review[END_REF][START_REF] Stock | Sampling techniques and preparation methods for microplastic analyses in the aquatic environment -a review[END_REF][START_REF] Guo | Source, migration and toxicology of microplastics in soil[END_REF][START_REF] Iroegbu | Plastics in municipal drinking water and wastewater treatment plant effluents: challenges and opportunities for South Africa -a review[END_REF][START_REF] Wong | Microplastics in the freshwater and terrestrial environments: prevalence, fates, impacts and sustainable solutions[END_REF]. The first studies have been conducted in the marine environment, mainly about macroplastics, (e.g., UNEP 2009;[START_REF] Hidalgo-Ruz | Microplastics in the marine environment: a review of the methods used for identification and quantification[END_REF], and started only some years ago in freshwater environments (e.g., Li et al. 2018b;[START_REF] Wagner | Freshwater microplastics: emerging environmental contaminants?[END_REF]. Plastics have also been investigated in rivers (Lin et al. 2018b;Rodrigues et al. 2018b), lakes (e.g., [START_REF] Eriksen | Microplastic pollution in the surface waters of the Laurentian Great Lakes[END_REF][START_REF] Turner | A temporal sediment record of microplastics in an urban lake, London, UK[END_REF], beaches [START_REF] Turra | Threedimensional distribution of plastic pellets in sandy beaches: shifting paradigms[END_REF]) and in the deep sea [START_REF] Kanhai | Deep sea sediments of the Arctic Central Basin: a potential sink for microplastics[END_REF].

The majority of plastic debris or microplastics (particles <5 mm) in the seas comes from the fragmentation of larger products (e.g., fishing net, household practices, bottles). There is growing evidence that microplastics also enters the water compartment directly from other sources, including cosmetics (nanoplastics used as ingredients), clothing and industrial processes [START_REF] Juliano | Cosmetic ingredients as emerging pollutants of environmental and health concern. A mini-review[END_REF]. Microfibers present in aquatic systems may also be released from the textile industries and from wastewater treatment plants (baths and washing clothes). Plastic microbeads are indeed present as abrasive scrubbers in personal care and cosmetic products (hand cleansers, toothpastes, facial scrubs, shampoos, etc.). Several studies have demonstrated the negative impacts of plastics and plastic debris on wildlife and the evidence of seafood contamination by microplastics, and therefore their potential effects on human health [START_REF] Avio | Plastics and microplastics in the oceans: from emerging pollutants to emerged threat[END_REF][START_REF] Juliano | Cosmetic ingredients as emerging pollutants of environmental and health concern. A mini-review[END_REF][START_REF] Barboza | Marine microplastic debris: an emerging issue for food security, food safety and human health[END_REF][START_REF] Da Costa | Micro(nano)plasticsanalytical challenges towards risk evaluation[END_REF][START_REF] Mishra | Marine microfiber pollution: a review on present status and future challenges[END_REF][START_REF] Prata | Methods for sampling and detection of microplastics in water and sediment: a critical review[END_REF][START_REF] Stock | Sampling techniques and preparation methods for microplastic analyses in the aquatic environment -a review[END_REF][START_REF] Guo | Source, migration and toxicology of microplastics in soil[END_REF]. From a scientific point of view, there is an urgent need for knowledge on the sources, fate and environmental concentrations over time [START_REF] Wong | Microplastics in the freshwater and terrestrial environments: prevalence, fates, impacts and sustainable solutions[END_REF].

The review by [START_REF] Barboza | Marine microplastic debris: an emerging issue for food security, food safety and human health[END_REF] showed the negative effects of plastics and plastic debris on marine fauna, and thus a potential effect on human health, due to the evidence of contamination of marine species (e.g., seafood) by microplastics, for example through the ingestion of microplastics as they are confounded with prey. However, data on the presence and occurrence of microplastics in marine species (and seafood in general) used for human consumption are scarce. This information is necessary for providing a basis for a sound risk assessment. Another important challenge is to understand the processes and mechanisms involved in the entry and assimilation of plastic debris into human tissues and their potential effects on human health. From a water engineering point of view, plastic-based debris are too small to be trapped in wastewater treatment plants. Therefore, they enter into water sources through domestic drainage systems and are transported to seas and oceans. Wastewater treatment plants should adopt innovative ideas to deal with this contamination.

A third example of substances of recent concern are nanoparticles, which are organic or inorganic particles that are smaller than 100 nm, widely used in consumer products (cosmetics, sunscreens, electronics, food), pharmacy, medicine, and chemical industry (nano-plasticizers, coatings, textiles, catalysis). Other sectors are also concerned, such as automotive parts, building materials, sports equipment, and energy [START_REF] Mearns | Effects of pollution on marine organisms[END_REF][START_REF] Zhao | Emerging pollutants -part I: occurrence, fate and transport[END_REF][START_REF] Marchi | Engineered nanomaterials: from their properties and applications, to their toxicity towards marine bivalves in a changing environment[END_REF][START_REF] Matich | Applications of metabolomics in assessing ecological effects of emerging contaminants and pollutants on plants[END_REF][START_REF] Sousa | Metal-based engineered nanoparticles in the drinking water treatment systems: a critical review[END_REF]. Indeed, research and development in nanotechnology (including nanoscience, nanomaterials, and nanoparticles) is booming. However, the development of a regulatory framework and environmental impact assessment tools concerning the potential toxicity of nanoparticles for the environment and/or health has not yet been completed. Unfortunately, this lack of regulatory control means that the increasing environmental exposure to nanoparticles is occurring without awareness of the general public about the exposure and potential environmental toxicity of these emerging contaminants. In recent years, the term nanotoxicity has been coined. Likewise, the terms nanopollution and nanopollutants are also increasingly being used, but there is still very little research on the presence and behavior of nanoparticles and nanoproducts in aquatic compartments, as well as on their impact on wastewater and waste treatment systems, and on the production of drinking water. These are important areas for future research by local scientific institutions. Like other emerging substances, existing wastewater treatment and water purification technologies are not primarily designed to deal with nanopollution/nanocontamination [START_REF] Sousa | Metal-based engineered nanoparticles in the drinking water treatment systems: a critical review[END_REF]. Nanoparticles have already been detected in wastewater, surface water, and treated drinking water, with concentrations ranging from ng/L to μg/L.

The scientific community is also increasingly concerned about the global contamination of water by other pollutants (Table 1.1), such as cosmetic ingredients (parabens, triclosan, bisphenol A) and UV filters (organic filters such as 2-ethylhexyl-methoxycinnamate, inorganic filters such as TiO 2 and ZnO), alkylphenols (detergents), rare earth elements (e.g., used in the production of electronic devices, mobile phones, super-capacitors, or as contrast agents in medical imaging), radioactive elements or radionuclides (some such as radium-226, radium-228 and uranium are natural groundwater contaminants; and thus contamination of drinking water is a significant, emerging issue), anti-retroviral drugs (used for human immunodeficiency virus), psychiatric drugs (antiepileptics such as carbamazepine used for the treatment of epilepsy and bipolar disorder, antidepressants such as selective serotonin reuptake inhibitors, anxiolytics such as benzodiazepines), cardiovascular drugs (beta-blockers such as atenolol), hypocholesterolaemic drugs, and biological agents such as pathogenic bacteria and antibiotic-resistance genes (Table 1.1). These substances are problematic because most of them: (1) are currently not regulated in humans and the environment; (2) are not systematically monitored as part of environmental and public health programs; and (3) have their mechanism of environmental and human toxicity poorly understood. There is an urgent need for scientific knowledge from a chemical, biological, toxicological and ecotoxicological point of view [START_REF] Gwenzi | Sources, behaviour, and environmental and human health risks of high-technology rare earth elements as emerging contaminants[END_REF][START_REF] Pedrazzani | Opinion paper about organic trace pollutants in wastewater: toxicity assessment in a European perspective[END_REF][START_REF] Xu | Occurrence and ecological risk of pharmaceuticals and personal care products (PPCPs) and pesticides in typical surface watersheds, China[END_REF][START_REF] Zhang | Decontamination of radioactive wastewater: state of the art and challenges forward[END_REF][START_REF] Olaniyan | Environmental water pollution, endocrine interference and ecotoxicity of 4-tert-octylphenol: a review[END_REF].

Another recent area of concern, not only for the public but also for the scientific community, is indoor pollutants [START_REF] Slezakova | Indoor air pollutants: relevant aspects and health impacts[END_REF][START_REF] Salthammer | Very volatile organic compounds: an understudied class of indoor air pollutants[END_REF][START_REF] Salthammer | Emerging indoor pollutants[END_REF][START_REF] Cretescu | Indoor air pollutants and the future perspectives for living space design. Indoor environment and health[END_REF]. It is recognized that indoor air is highly polluted: 5-10 times more polluted than outdoor air. There are many sources of indoor air pollution (at home as well as in offices), such as combustion and tobacco products (gas appliances, tobacco smoke, candles), cooking processes, building materials and furnishings, cleaning and personal care products (perfumes), paints, central heating and cooling systems, humidity, and other sources (indoor and outdoor particulate matter, biological agents, etc.). Chemical (volatile organic compounds, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated biphenyl ethers, particulate matter, radioelements such as radon, pesticides, etc.) and biological (pollens, bacteria, and mold) pollutants can accumulate to levels that can cause health, nuisance and comfort problems [START_REF] Slezakova | Indoor air pollutants: relevant aspects and health impacts[END_REF]. The comprehensive review recently published by [START_REF] Salthammer | Emerging indoor pollutants[END_REF] can be consulted on emerging indoor pollutants.

Biological Agents

In recent years, cases of fatal emerging/re-emerging viral infections have significantly affected human health despite extraordinary advances in biomedical knowledge. The recurrent epidemics of dengue and chikungunya in tropical and subtropical regions, the Zika epidemic in the Americas and the Caribbean, and the global SARS epidemics and Covid-19 pandemics are dramatic examples.

Like chemical hazards, biological threats are part of our societies. Indeed, biological agents are ubiquitous in the environment and in our daily lives. Since they are invisible, it is difficult to assess the risks they present. According to the European Directive 2000/54/EC, the four main groups of biological agents are: bacteria, viruses, parasites, and fungi. In this Directive, biological agents are also defined as "the micro-organisms, including those which have been genetically modified, cell cultures and human endoparasites, which may be able to provoke any infection, allergy or toxicity" (European Directive 2000/54/EC). A microorganism is defined as a microbiological entity, cellular or non-cellular, which is capable of replication or of transferring genetic material. A cell culture is defined as the in-vitro growth of cells derived from multicellular organisms. Like any other organism, a biological agent simply tries to live and procreate [START_REF] Parvez | Evolution and emergence of pathogenic viruses: past, present, and future[END_REF]. Pathogenic microorganisms are present in the secretions, feces, urines of patients or asymptomatic carriers, subsequently retrieved in the wastewater, the wastewater treatment plants, and the receiving surface water. Hence, pathogenic biological agents can be considered as emerging pollutants.

Pathogens are organisms/microorganisms able to cause diseases. A minor part of organisms/microorganisms are pathogens. They include viruses, bacteria, fungi, and parasites, which can be found anywhere in the environment, including water, air, food, soil, and surfaces we are in contact with at home. Every pathogen needs a host to grow and survive. Once the pathogen has settled in a host, it must avoid the host immune responses, and thrive before being transmitted to a new host. Pathogens can be transmitted in several ways depending on their type: through skin contact, body fluids, airborne particles, water and food, contact with feces, and contact with a contaminated surface.

Viruses are responsible for a number of infections, many of which are contagious. Examples of viruses causing viral diseases include human immunodeficiency virus (HIV), dengue virus, rotavirus, and coronavirus. They are made up of a piece of genetic code (DNA or RNA) and protected by a coating or protein. Depending on the type of virus, they can cause a wide range of acute or chronic respiratory, gastrointestinal, or genital infections. However, viruses are unable to thrive and reproduce independently. Hence, viruses use the components of the host cell to replicate, damage or destroy the infected cells, before being released. There are efficient vaccines and antiviral treatments for some, but not for all, viral diseases.

Bacteria are microorganisms made of a single cell that can live almost everywhere on Earth. They are more complex organisms than viruses that can thrive independently of a host. Only a few bacterial species cause infections. Indeed, some species are beneficial (e.g., those present in dairy products or in human gut), others are harmful (e.g., those causing infections such as tuberculosis are called pathogenic bacteria). Examples of bacterial infections are gastroenteritis, meningitis, tuberculosis, and Lyme disease. Some bacterial diseases can be prevented by vaccination. Bacterial infections are treated by antibiotics.

Fungi can be found naturally in the environment, and also on the human skin. Some of them cause infections and the structure of their cell walls can make them resistant to antifungal agents. Some new species of fungi, such as Candida auris, are especially pathogenic. Parasites are organisms that behave like tiny animals, living in or on a host and feeding from or at the expense of the host. Three main types of parasites (i.e., protozoa, helminths and ectoparasites) can cause diseases (e.g. malaria) in humans. They can be spread after an insect bite or contamination by soil, water, or air.

Antibiotic-resistant bacteria and antibiotic resistance genes have recently been identified as the greatest threats to public health by the World Health Organization. They are a potential hazard to public safety and water quality. The contamination of wastewater systems by antibiotic-resistance genes and the global spread of antibiotic-resistant superbugs is of great concern. Indeed, an area of great interest to the scientific community is the phenomenon of bacterial resistance [START_REF] Zad | Fate of environmental pollutants[END_REF][START_REF] Zhao | Emerging pollutants -part I: occurrence, fate and transport[END_REF][START_REF] Kumar | Antibiotics bioremediation: perspectives on its ecotoxicity and resistance[END_REF][START_REF] Liu | Emerging pollutants -part II: treatment[END_REF][START_REF] Ng | Fate of environmental pollutants[END_REF][START_REF] Reichert | Emerging contaminants and antibiotic resistance in the different environmental matrices of Latin America[END_REF][START_REF] García | A review of emerging organic contaminants (EOCs), antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs) in the environment: increasing removal with wetlands and reducing environmental impacts[END_REF]. Some bacterial clones have become resistant to most of the antibiotics, even to the last-resort compounds carbapenems or colistin, making the associated infections difficult to treat. This is due to the overuse of antibiotics by humans and animals. However, studies have also linked the use of antibiotic in agriculture with infections in humans caused by antibiotic-resistant microbes. The great majority of pharmaceuticals consumed by humans and animals end up in feces and urine, which reach sewage treatment plants and/or soil. In addition, the gut of animals and human is the major reservoir of antibiotic-resistant bacteria. Since wastewater treatment plants are not designed to eliminate pharmaceuticals or antibiotic-resistant bacteria, treated effluents still contain pharmaceuticals (e.g., antibiotics, hormones) and antibiotic-resistant microorganisms. In addition, the manure produced by animals receiving antibiotics that is commonly used as fertilizer, can become a source of antibiotics and antibiotic-resistance determinants for soils and crops. Besides, in areas affected by water scarcity, wastewater reuse is becoming a common practice in agriculture, potentially introducing these emerging pollutants into the food chain. In fact, there is still very little information on antibiotic resistant organisms in water sources, drinking water treatment plants and drinking water distribution systems, and the impact of their presence on human health. There is also an urgent need to improve understanding of the mechanisms associated with the spread and development of these organisms, not only in treatment plants and the environment (water, sediment, and soil), but also in the human body and in clinical and veterinary settings (see the two chapters devoted to these topics in this book).

Analysis and Detection of Emerging Contaminants

The proliferation of chemical substances, both known and unknown, that can have adverse effects on human health and the environment has increased the need for early detection for the safe identification of these contaminants. High-performance analytical tools and validated protocols now exist to identify and quantify contaminants in various environmental matrices. All water stakeholders concerned with water pollution issues, whether they are university researchers, government agencies, regulatory bodies or environmental interest groups, have tools at their disposal that allow them to collect and evaluate data from a variety of sources. These data are important for advancing knowledge about emerging substances and for preparing future regulatory or monitoring requirements.

Chromatographic Methods Coupled to Mass Spectrometry for the Analysis of Emerging Contaminants

The increase of the production, as well as consumption, of compounds designed to improve health, leads to their increased release into the environment. The governments try to regulate this impact into the environment with emission limits for different chemicals and the societies try to minimize, with the available technology, the amount of these pollutants that end up in aquatic ecosystems (IOM 2014). The complexity of the chemical mixtures that are present in the environment demands that the scientific community works on increasingly sensitive methods for the analysis of these compounds, as shown in Table 1.1.

When planning to study contaminants in environmental matrices, it is necessary to develop an entire study design. Within this study design, the following points need to be considered: (1) sampling, (2) sample preparation, (3) chemical analysis, as well as (4) data visualization and analysis.

The collection of samples requires a previous study to make them representative. The previous study should depend on a great extension of the target chemicals or the expected concentrations, as well as on the information to be extracted from the results [START_REF] García-Córcoles | Chromatographic methods for the determination of emerging contaminants in natural water and wastewater samples: a review[END_REF]. For example, for a study involving pesticide analysis, the areas to be selected should be those where the major economic activity is agriculture, or in the case of a study of pharmaceuticals, it should be based on population density and age.

Sample Collection and Preparation

For the study of contamination/pollution, water is usually the most often investigated environmental matrix due to its physicochemical characteristic and since it is relatively easy to analyse and is in nature an important reservoir of pollutants in Nature. These samples are usually collected from surface water, wastewater treatment plants, groundwater or even drinking water. There are two predominant methods of sample collection: grab samples or composite samples. When performing grab sampling, a certain volume of water is collected at a specific time and place. The sampled amount of water is usually relatively small. This type of sampling is usually performed only when contaminant concentrations can be expected to be high and hence easy to detect with analytical methods. The second method is more complex since the sampling is performed with a time window that can last from hours to days. It is often used to observe a wider range of contaminants or when relatively low concentrations are expected and are more difficult to detect with simple techniques. An example is the so-called large volume solid phase extraction in which the selected site is sampled for a certain time and the sample is filtered into solid phase extraction cartridges. The contaminants are accumulated and can subsequently be extracted in the laboratory [START_REF] Schulze | Assessment of a novel device for onsite integrative large-volume solid phase extraction of water samples to enable a comprehensive chemical and effect-based analysis[END_REF].

Not many methods perform direct analysis of samples. Most of the studies in water perform pre-concentration techniques using solid phase extraction [START_REF] Carmona | The use of chromatographic methods coupled to mass spectrometry for the study of emerging pollutants in the environment[END_REF][START_REF] De Alda | Liquid chromatography-(tandem) mass spectrometry of selected emerging pollutants (steroid sex hormones, drugs and alkylphenolic surfactants) in the aquatic environment[END_REF][START_REF] Dimpe | Current sample preparation methodologies for analysis of emerging pollutants in different environmental matrices[END_REF] since they are considered relatively cheap, fast, reliable and reproducible methods [START_REF] Tang | Emerging pollutants in water environment: occurrence, monitoring, fate, and risk assessment[END_REF].

Solid phase extraction is the most widely used extraction technique for environmental samples [START_REF] Dimpe | Current sample preparation methodologies for analysis of emerging pollutants in different environmental matrices[END_REF][START_REF] Carmona | The use of chromatographic methods coupled to mass spectrometry for the study of emerging pollutants in the environment[END_REF][START_REF] Lorenzo | Analytical challenges to determine emerging persistent organic pollutants in aquatic ecosystems[END_REF][START_REF] García-Córcoles | Chromatographic methods for the determination of emerging contaminants in natural water and wastewater samples: a review[END_REF] and is an effective tool for isolating and purifying compounds. The retention of emerging contaminants was improved thanks to the development of new polymeric sorbents, which are mainly made by hydrophilic-hydrophilic material [START_REF] Wille | Coupled chromatographic and mass-spectrometric techniques for the analysis of emerging pollutants in the aquatic environment[END_REF]. Nowadays, most of the studies with solid phase extraction techniques use Oasis ® HLB cartridges (divinyl benzene and vinylpyrrolidone copolymer) followed by StrataX ® cartridges (polymeric reversed phase that provides a strong retention of neutral, acidic and basic compounds). Another widely used method for the extraction of emerging pollutants is the liquid-liquid extraction, although this can be time consuming (due to its complex automation), difficult and expensive, since a large volume of organic solvents is needed. Furthermore, this procedure requires a subsequent clean-up and a preconcentration phase prior to the chromatographic analysis [START_REF] Wang | Characterization, treatment and releases of PBDEs and PAHs in a typical municipal sewage treatment plant situ-ated beside an urban river, East China[END_REF][START_REF] García-Córcoles | Chromatographic methods for the determination of emerging contaminants in natural water and wastewater samples: a review[END_REF]).

In the case of solid matrices, such as sediments, soils or biota, the Quick, Easy, Cheap, Effective, Rugged and Safe (known as QuEChERS) method developed by [START_REF] Anastassiades | Fast and easy multiresidue method employing acetonitrile extraction/partitioning and "dispersive solid-phase extraction" for the determination of pesticide residues in produce[END_REF] is frequently used for the extraction of emerging contaminants [START_REF] Calatayud-Vernich | Efficiency of QuEChERS approach for determining 52 pesticide residues in honey and honey bees[END_REF]. This method was optimized for the extraction of pesticides from fruits and consists mainly of two phases: extraction and clean-up. The extraction phase uses salts, such as MgSO 4 , to reduce the water content, and others such as NaCl, sodium acetate or citrate salts for all other applications. For the clean-up step, the use of primary/secondary amine stands out for the elimination of, among others, organic acids, fatty acids, sugars and atrazine pigments, or the sorbent C18 that eliminates fats, sterols and other non-polar interferences. Other methods have been optimized over the years for the extraction of a greater number of compounds, such as solid-liquid extraction. A method using solid-liquid extraction with a McIlvaine-EDTA buffer (pH = 5.5) accompanied by solid phase extraction was described by [START_REF] Carmona | Multi-residue determination of 47 organic compounds in water, soil, sediment and fish-Turia River as case study[END_REF] as an improvement of the traditional QuEChERS. The method using McIlvaine-EDTA buffer reduces matrix effects to less than 20% and provides recoveries above 50%. In addition, more extracted compounds have been detected in studies with screening analysis. Other methods for the extraction of organic contaminants in solid matrices are based on the technique of pressurized liquid extraction which requires solvents at high temperatures and pressures that may transform some analytes into different transformation products.

Instrumental Analysis

In recent years, the number of scientific publications that focused on the study of emerging contaminants in aquatic ecosystems has increased exponentially. Most of these publications base their analyses on a multitude of chromatographic techniques coupled with mass spectrometry as shown in recent reviews (Fig. 1.3) [START_REF] Carmona | The use of chromatographic methods coupled to mass spectrometry for the study of emerging pollutants in the environment[END_REF][START_REF] Lorenzo | Analytical challenges to determine emerging persistent organic pollutants in aquatic ecosystems[END_REF][START_REF] García-Córcoles | Chromatographic methods for the determination of emerging contaminants in natural water and wastewater samples: a review[END_REF][START_REF] Tang | Emerging pollutants in water environment: occurrence, monitoring, fate, and risk assessment[END_REF][START_REF] Álvarez-Ruiz | Analysis of emerging and related pollutants in aquatic biota[END_REF]. Chromatography is a physical method of separation in which the components are separated and distributed between two phases, a stationary and a mobile phase. The Russian botanical Mikhail Tsvett thus conceived it in 1903 based on the ability of a column of finely powdered solid materials such as Al 2 O 3 , to adsorb substances from a solution that drips through it. Tsvett used this method to separate coloured components of plant pigments. The column developed its colour bands, and this technique was called chromatography separation. The Tsvett method remained unknown for a long time until switched back to biochemists in the 1930s.

The first type of chromatography is known as adsorption chromatography. In 1942, Archer Martin and Richard Synge co-developed the partition chromatography by using a liquid absorbed on a solid as the stationary phase and the other immiscible liquid stationary phase as mobile phase. In this method, called liquid-liquid chromatography, the compounds are distributed into two liquid phases. This achievement inspired the development of other separation methods, namely gas chromatography. The effectiveness of liquid-liquid chromatography was increased in the 1970s by the use of small particles for support and by pumping fluid, in order to enhance the mobile phase through the stationary phase under pressure. This method is known as high Pressure liquid chromatography. With the various chromatography techniques, it is possible to separate and detect compounds quantities of components (parts per billion and even parts per trillion). Chromatography effectiveness is even higher when combined with other instruments such as with mass spectrometry for analysis.

One of the main reasons for the delay in the application of liquid chromatographymass spectrometry was the difficulty involved with the coupling liquid chromatography and mass spectrometry. From the 70s several liquid chromatography-mass spectrometry interfaces have been developed, but it was only after commissioning of atmospheric pressure interfaces (electrospray ionization and atmospheric pressure chemical ionization) when liquid chromatography-mass spectrometry began to be a robust alternative to the methods of gas chromatography-mass spectrometry.

Advances in chromatographic techniques have led to increased detection of analysis of emerging contaminants (in the order of ng/L or μg/L). The most used techniques for the separation of these compounds are the gas chromatography and the liquid chromatography. The selection of one of them depends on the physicalchemical properties of the compounds to be detected. Volatile and semi volatile compounds are analysed in the gas chromatograph, such as phenols or phtalates and non-volatile ones in the liquid chromatograph [START_REF] Tousova | European demonstration program on the effect-based and chemical identification and monitoring of organic pollutants in European surface waters[END_REF][START_REF] Lebedev | Detection of semi-volatile compounds in cloud waters by GCxGC-TOF-MS. Evidence of phenols and phthalates as priority pollutants[END_REF]. According to most of the literature reviews consulted, an average of 80% of the studies use liquid chromatograph versus gas chromatograph. Both techniques require the use of columns for the compounds separation. In Liquid Chromatography, the most common mode is reverse phase separation which is characterized by a stationary phase that is less polar than the mobile phase [START_REF] Rennie | Dictionary of chemistry[END_REF]. Columns that are characterized by this type of separation have stationary phases with long chains of aliphatic carbons attached to silica with pores of the micrometric order. The silica columns most used in liquid chromatography are those with 8 or 18 hydrocarbon chains (C8 and C18), being the C18 column the most used due to the robustness offered through the retention of both polar and nonpolar analytes. In the case of gas chromatography, the most used columns are capillary ones between 30 and 60 m, due to their efficiency, high resolution and speed (Zhang et al. 2016b). These types of columns usually have a diameter between 0.1μm and 0.5μm. These columns can be classified into three different types: support coated open tubular, porous layer open tubular and wall coated open tubular column, being the last one the most used (Dettmer-Wilde and Engewald 2014; [START_REF] Baduel | Development of sample extraction and clean-up strategies for target and non-target analysis of environmental contaminants in biological matrices[END_REF].

When designing a method for analysis and depending on both the equipment available and the compounds to be identified, a robust and stable mobile phase selection is important. The mobile phase is used to transport the analytes to the stationary phase. It can also play an important role in the separation of compounds in the case of liquid chromatography. The mobile phase in liquid chromatography analysis generally consists of two solvents. One is an aqueous type (A) and the other is an organic solvent (B) and generally includes an acid or salt to improve separation. The mixture ratio of both constituents usually changes over time of analysis to allow a better elution of the compounds in the column. The most common organic solvents used are methanol or acetonitrile. These are supplemented by a salt, in the case of the negative ionization mode for further mass spectrometry detection, such as ammonium acetate, ammonium formate or ammonium fluoride. The latter has been demonstrated to improve chromatographic signals, compared to other salts and also to improve the capacity and efficiency of electrospray [START_REF] Carmona | Occurrence of acidic pharmaceuticals and personal care products in Turia River Basin: from waste to drinking water[END_REF]) for the study of some emerging pollutants such as pharmaceuticals, illicit drugs and personal care products. For the positive ionization mode, the most commonly used acids are acetic acid and formic acid [START_REF] Carmona | Multi-residue determination of 47 organic compounds in water, soil, sediment and fish-Turia River as case study[END_REF][START_REF] Sadutto | Systematic assessment of extraction of pharmaceuticals and personal care products in water and sediment followed by liquid chromatographytandem mass spectrometry[END_REF][START_REF] Álvarez-Ruiz | Analysis of emerging and related pollutants in aquatic biota[END_REF]. In gas chromatography the mobile phase is usually an inert gas such as helium or another non-reactive gas such as nitrogen. Helium is usually the most used gas (about 90%) (Li et al. 2019b) for the transport of analytes. Chromatographs have been evolving, including increasing their pressure or increasing their capacity for the use of more than two mobile phases at the same time. Chromatography is a technique that is usually coupled to tandem with mass spectrometry for environmental analysis.

Mass spectrometry is a universal and specific instrumental technique, highly sensitive, which enables the unequivocal identification of a substance. The principle of the mass spectrometry is the production of ions from neutral compounds and observing the subsequent decomposition of these ions in "product ions". These ions decomposed (fragments also possess charge) move quickly and are classified according to their ratio m/z (ratio between mass and charge number of the ion). The mass spectrometer not only classifies the fragments, but also measures the amount that is formed. When a molecule is supplied with a given energy, the molecule is decomposed in a certain pattern, which fragments are always obtained at the same intensity ratio. This particular pattern is plotted in the mass spectrum, which, for this reason, is called the fingerprint of the substance. Thus, the mass spectrum allows the unequivocal identification of the molecules.

Mass spectrometers are generally sophisticated instruments, which comprise: (A) sample introduction system, that may be, in this case, a liquid chromatograph; (B) an ionization source, where the molecular fragmentation characteristic of each compound occurs; (C) a mass analyser or filter which separates the ion fragments generated according to their mass/charge ratio and (D) a detector, which collects and characterizes the fragment ions leaving the analyser. This instrumental technique is the most used for the determination and identification of emerging contaminants. This is a method with many different uses, ranging from forensics to health research, as well as for the study of the environment, since it is highly sensitive and reliable. There are different types of mass spectrometers depending on the objective of the study. Among them, for the study of emerging contaminants, the triple quadrupole (QqQ), the time of flight (TOF) and the orbitrap stand out. The most common mode for the study of emerging contaminants is electrospray ionization.

In studies on emerging pollution, the most widely used technique with mass spectrometry is the so-called target analysis or target screening, i.e., studies to identify and quantify a series of known compounds in complex matrices [START_REF] Krauss | LC-high resolution MS in environmental analysis: from target screening to the identification of unknowns[END_REF][START_REF] Ccanccapa-Cartagena | Suspect, non-target and target screening of emerging pollutants using data independent acquisition: assessment of a Mediterranean River basin[END_REF]. This technique requires a series of reference standards for the quantification and confirmation of the compound. The triple quadrupole consists of three quadrupoles connected in series. Quadrupole 1 (Q1) and the quadrupole 3 (Q3) operate as two quadrupole analysers connected in series. The quadrupole 2 (q2) or collision cell is placed in between Q1 and Q3. It is a special quadrupole in which energy is applied. The collision energy, that allows fragment ions, is obtained in the ionization source. This energy can take different values, which allows different fragments and/or different intensity relationships between them in mass spectra. This instrumental technique is highly sensitive and selective.

Another widely used technique is suspect screening. The suspect screening method implements an identification of expected compounds using databases (libraries) for their identification. This method, which has the so-called known unknowns approach, starts with a list of expected substances. Unlike the target analysis, it is not based on reference standards for confirmation and quantification, but on the specific information available for the compound, such as the molecular formula (which allows the calculation of the m/z of the expected ion). In contrast to this technique, non-target screening starts without any information about the compounds to be detected. The number of chemically significant structures that can be assigned to a particular peak is limited to those structures that show a close relationship with the original compound [START_REF] Krauss | LC-high resolution MS in environmental analysis: from target screening to the identification of unknowns[END_REF]. The most common mass spectrometers for this type of analysis are the QToF (time-of-flight mass spectrometry) or the orbitrap (ion trap), the latter being the least used [START_REF] Andrés-Costa | Universal method to determine acidic licit and illicit drugs and personal care products in water by liquid chromatography quadrupole time-of-flight[END_REF]). In the QToF, which is the most used for the realization of these techniques, after the ions have crossed the quadrupole, they reach an ion button in which a high voltage pulse is applied that accelerates the ions in the so-called flight tube. An ion mirror at the end of the tube reflects the ions which sends them to the detector and records their time of arrival. The time of flight for each mass is unique and is determined by the energy at which the ion is accelerated, the distance and the m/z.

For the analysis of the obtained data, although each device has its specific software, nowadays there are new open-source softwares, such as MZmine. This can identify the compounds as well as integrate them for their later quantification. This type of software can be used for target, suspect and non-target screening.

Detection of Microplastics in Water and Sediment

Plastics in environmental samples are usually size categorized in macroplastics (>25 mm; MSFD Technical Subgroup on Marine Litter, MSFD 2013), mesoplastics (5-25 mm) and microplastics (<5 mm). Microplastics may further be differentiated in size classes of 1-5 mm (large microplastics) and <1 mm (small microplastics; [START_REF] Galgani | Marine litter within the European marine strategy framework directive[END_REF] or different size fractions (1-5 mm, 0.5-1 mm, 100-500μm, 50-100μm, 10-50μm, 5-10μm and 1-5μm; [START_REF] Braun | Microplastics analytics sampling, preparation and detection methods. Discussion paper within the scope of the research focus plastics in the environment sources, sink, solutions[END_REF]. Furthermore, different forms of microplastics are distinguished (e.g. fragments, fibers, films, spheres). Figure 1.4 shows different microplastic forms from the Elbe River, Germany. Primary microplastics mostly consist of small-sized industrially manufactured pellets (microbeads) which are used in personal care products [START_REF] Fendall | Contributing to marine pollution by washing your face: microplastics in facial cleansers[END_REF] or for further processing [START_REF] Thompson | Microplastics in the marine environment: sources, consequences and solutions[END_REF]. Secondary microplastics refer to a fragmentation of larger pieces of plastics during use or because of weathering in the environment [START_REF] Barnes | Accumulation and fragmentation of plastic debris in global environments[END_REF][START_REF] Thompson | Microplastics in the marine environment: sources, consequences and solutions[END_REF]. It includes fragments of plastic litter in aquatic environments and on land [START_REF] Ryan | Monitoring the abundance of plastic debris in the marine environment[END_REF], films from agricultural use [START_REF] Astner | Mechanical formation of micro-and nano-plastic materials for environmental studies in agricultural ecosystems[END_REF] or fibers from textiles [START_REF] Carr | Transport and fate of microplastic particles in wastewater treatment plants[END_REF]. Although many researchers intensively studied microplastics in the water and sediment, the results are difficult to compare. A first suggestion for standardized sampling has been published by [START_REF] Frias | Standardised protocol for monitoring microplastics in sediments[END_REF] for sediments. ISO TC 61/SC 14 (ISO/CD 23187; ISO 2020) is currently also working on a standardization for microplastic preparation and analytics.

Studying environmental samples for microplastic analysis is complex as the polymers are not only influenced by their manifold characteristics [START_REF] Hartmann | Are we speaking the same language? Recommendations for a definition and categorization framework for plastic debris[END_REF], but may also be altered by the development of biofilms [START_REF] Oberbeckmann | Marine microplastic-associated biofilms -a review[END_REF], hetero-aggregates or sorbed pollutants [START_REF] Guo | The chemical behaviors of microplastics in marine environment: a review[END_REF]. For identifying microplastics in water and sediment, the samples most often have to be treated beforehand. Microplastics are relatively small and difficult to detect in environmental samples. Sediment and soil usually contain a high content of organic matter which hampers the identification by means of e.g. Raman spectroscopy or Fourier transform infrared (FTIR) spectroscopy. Therefore, the sample volume has to be reduced (for sediments e.g., by means of sieving and a size fractionation; water and sediment samples: digestion of organics, density separation). The most common procedure for water and sediment samples is organic digestion with acids, bases, oxidizers or enzymes before measuring the samples [START_REF] Stock | Sampling techniques and preparation methods for microplastic analyses in the aquatic environment -a review[END_REF]. These solutions may however affect synthetic polymers, e.g., degrade, discolorate or dissolute them [START_REF] Cole | Microplastics as contaminants in the marine environment: a review[END_REF]. Therefore, samples only have to be treated when a high amount of suspended matter is present.

Before measuring the samples, most researchers separate minerals (e.g., >2.5 g/ cm 3 for quartz, feldspar and calcite) from organics and polymers (<0.01 and >1.4 g/ cm 3 , e.g., foamed polystyrene and polyvinyl-chloride; Hidalgo-Ruz et al. 2012). Microplastics will generally float and minerals sink to the ground. Different density solutions are usually used: sodium chloride, zinc chloride, sodium iodide, sodium bromide, sodium polytungstate or potassium formate [START_REF] Stock | Sampling techniques and preparation methods for microplastic analyses in the aquatic environment -a review[END_REF]. Depending on the density of the solution (>1.2 g/cm 3 ), only parts or all polymers are recovered from environmental samples. The same holds true as for organic digestion; density separation is only necessary when the sample contains a larger part of inorganic material. Contamination of samples also has to be taken into account. During preparation and analysis, especially air-borne fibers may contaminate the samples [START_REF] Dris | A first overview of textile fibers, including microplastics, in indoor and outdoor environments[END_REF]. Therefore, a blank sample for checking the contamination during preparation and measuring is absolutely needed in order to detect external contamination.

For identifying polymers, different analytical methods have been developed. Depending on the specific research question, one of these methods is chosen rendering information about quantity, quality or mass. Visual identification of plastic particles allows a first preliminary evaluation, description, photograph and measurement of larger plastic particles [START_REF] Löder | Methodology used for the detection and identification of microplastics -a critical appraisal[END_REF]. Digital, visual or light microscopes are usually used to identify particles. Visual identification is based on polymer-specific characteristics such as color, form, absence of organic structures or equal thickness of fibers [START_REF] Norén | Small plastic particles in Coastal Swedish waters[END_REF]. Hidalgo-Ruz et al. ( 2012) recommends a size of >500μm or >1 mm as smaller particles may be confounded with inorganic or organic material. However, as this method is subjective and only larger particles are taken into account, all particles have to be verified later by means of FTIR, Raman or pyrolysis.

The most common methods for identifying microplastics are FTIR spectroscopy, Raman spectroscopy and pyrolysis gas chromatography-mass spectrometry (GC-MS). Furthermore, research is conducted with thermal extraction and desorptiongas chromatography mass spectrometry [START_REF] Dümichen | Fast identification of microplastics in complex environmental samples by a thermal degradation method[END_REF], scanning electron microscopy coupled with energy dispersive X-ray spectroscopy [START_REF] Gniadek | The marine nano-and microplastics characterisation by SEM-EDX: the potential of the method in comparison with various physical and chemical approaches[END_REF] or quantitative nuclear magnetic resonance spectroscopy [START_REF] Peez | Quantitative analysis of PET microplastics in environmental model samples using quantitative 1H-NMR spectroscopy: validation of an optimized and consistent sample clean-up method[END_REF].

FTIR spectroscopy allows identifying single particles of a sample by absorbing IR radiation in reflection or transmission mode. Each infrared spectrum of a sample is compared to a reference spectrum and can thus be identified [START_REF] Löder | Methodology used for the detection and identification of microplastics -a critical appraisal[END_REF]. Selected particles >500μm can be measured with an ATR-FTIR (attenuated total reflectance), smaller ones (>10μm) with a μFTIR which is very timeconsumptive. μFTIR measurements in transmission mode are feasible with transparent filters (e.g. aluminum oxide) and thin samples. If water is present, particles are black or too thick (50-100μm), the IR radiation is totally absorbed and thus no identification is possible. In order to measure an entire filter, a focal plane array may be coupled to the FTIR which identifies automatically all particles present.

Raman spectroscopy detects the molecular composition by investigating its vibrational and rotational frequencies with lasers and wavelengths from 500 nm to 1064 nm. The spectral fingerprint of a chemical structure allows the determination of the specific polymer. The basis of a Raman is the Raman shift which is the difference of Rayleigh photons and inelastically scattered photons [START_REF] Mcnesby | Handbook of vibrational spectroscopy[END_REF][START_REF] Kuhar | Challenges in application of Raman spectroscopy to biology and materials[END_REF]. Such as the μFTIR, μRaman is used for measuring small particles (>1μm) and is also time-consumptive when analyzing singe particles. Raman and FTIR are complementary methods as the signals are stronger in Raman and weaker in IR. The advantage of Raman spectroscopy is that water does not influence the measurement and that a higher depth can be reached, i.e. more particles can be measured and identified. However, samples need to be well prepared as organic/inorganic particles may lead to fluorescence influencing the spectra and Raman measurements are still time-consuming [START_REF] Dris | Microplastic contamination in an urban area: a case study in greater Paris[END_REF].

Pyrolysis gas chromatography mass spectrometry renders qualitative information about one single particle or quantitative information by calculating the mass of selected plastic polymers in environmental matrices. Moreover, plastic additives might be measured. Molecules are thermally degraded to determine their chemical composition by using a gas chromatograph for separation and a mass spectrometer for identification [START_REF] Käppler | Comparison of μ-ATR-FTIR spectroscopy and py-GCMS as identification tools for microplastic particles and fibers isolated from river sediments[END_REF][START_REF] Dierkes | Quantification of microplastics in environmental samples via pressurized liquid extraction and pyrolysis-gas chromatography[END_REF]). The measured pyrograms are compared to a library with the most common polymer types. The disadvantage of pyrolysis gas chromatography mass spectrometry is that particles can only be used once, as they are destroyed during the measurement.

In summary, microplastics are small plastic/polymer fragments in debris of various sizes that have accumulated in the global environment, particularly in all major marine habitats from the poles to the equator, from the sea surface and coastline to the depths. Techniques and methodologies for evaluating the detection of microplastics in aqueous environments are available. However, the detection and quantification of plastics in environmental matrices is currently an analytical challenge due to the laborious and varied analytical procedures currently used [START_REF] Barboza | Marine microplastic debris: an emerging issue for food security, food safety and human health[END_REF]. Indeed, the comparability of data on microplastics is currently hampered by a wide variety of different methodologies, resulting in the production of data of widely differing quality and resolution. Recently, da Costa et al. ( 2019) and [START_REF] Prata | Methods for sampling and detection of microplastics in water and sediment: a critical review[END_REF] also highlighted the difficulty comparison of data obtained in different studies due to the lack of standardized sampling protocols, methodologies and techniques for their identification and quantification, because of the many different characteristics of polymers. A critical evaluation of the methodologies used for the detection and identification of microplastics is necessary. Environmental research on these materials is also not consensual and definitions are unclear [START_REF] Barboza | Marine microplastic debris: an emerging issue for food security, food safety and human health[END_REF]. The classification of plastics is not a trivial issue. Recently, the term nanoplastics (<100 nm) has been introduced but there is no universally agreed definition. In addition, there are no established standard methods yet to accurately establish their ecotoxicological effects. This aspect is also of interest to the scientific community.

Emerging Contaminants in the Environment

Occurrence, Fate and Toxicity of Alkylphenols in the Aquatic Environment

Alkylphenols are a group of chemicals used in the production of surfactants, resins, antioxidants, pesticides, construction materials and automobile supplies [START_REF] Ying | Environmental fate of alkylphenols and alkylphenol ethoxylates_a review[END_REF][START_REF] Lamprea | Alkylphenol and bisphenol A contamination of urban runoff: an evaluation of the emission potentials of various construction materials and automotive supplies[END_REF]. Nonylphenol ethoxylates and octylphenol ethoxylates are the most common non-ionic surfactants. When nonylphenol ethoxylates and octylphenol ethoxylates are released to wastewater treatment plants and environmental matrices, they are subjected to incomplete biodegradation, leading to the formation of nonylphenol and octylphenol [START_REF] Fairbairn | Contaminants of emerging concern: mass balance and comparison of wastewater effluent and upstream sources in a mixed-use watershed[END_REF][START_REF] Xu | Occurrence, fate, and risk assessment of selected endocrine disrupting chemicals in wastewater treatment plants and receiving river of Shanghai, China[END_REF].

Nonylphenol and octylphenol can also be leached from concrete, elastomeric bitumen, and tires in runoff [START_REF] Lamprea | Alkylphenol and bisphenol A contamination of urban runoff: an evaluation of the emission potentials of various construction materials and automotive supplies[END_REF]). Short-chain alkylphenols, such as 4-tert-butylphenol and 4-tert-pentylphenol, are often present in building materials such as paints, coating, and adhesives [START_REF] Janousek | Combined study of source, environmental monitoring and fate of branched alkylphenols: the chain length matters[END_REF]. Some alkylphenols, e.g., 6-di-tert-butyl-4-methylphenol, are also used as antioxidants in food and cosmetics [START_REF] Lu | Distribution and fate of synthetic phenolic antioxidants in various wastewater treatment processes in Canada[END_REF]. Produced water discharges from offshore oil and gas production can be an important source for some alkylphenols (C1-C3) in the marine environment [START_REF] Lofthus | Biotransformation of potentially persistent alkylphenols in natural seawater[END_REF]. Alkylphenols are known as environmental endocrine disruptors, and their levels in some areas may exceed water quality criteria [START_REF] Zhang | Criteria for assessing the ecological risk of nonylphenol for aquatic life in Chinese surface fresh water[END_REF]. Alkylphenols are therefore recognized as emerging contaminants of concern and, in the European Water Framework Directive (2013/39/EU), nonylphenols (in particular 4-para-nonylphenol) and octylphenols (4-tertoctylphenol) are classified as priority substances.

Occurrence Nonylphenol and octylphenol are frequently detected in the aquatic environment worldwide due to their widespread use (Table 1.2). It should be noted that nonylphenol or technical nonylphenol is a mixture of alkylphenols with different carbon chain lengths, branching, and substitution positions. Technical nonylphenol consists mostly of 4-nonylphenol, which is theoretically composed of 211 isomers, and 4-n-nonylphenol is the linear isomer. Similarly, 4-tert-octylphenol is one of the isomers of octylphenol. Most of the recent reports on nonylphenol and octylphenol are from China (Table 1.2). The highest levels have been reported from Guangzhou, the largest city in Pearl River Delta, where maximum concentrations of nonylphenol in river water and sediment were 5050 ng/L and 14,400 ng/g, respectively [START_REF] Xu | Tracking major endocrine disruptors in coastal waters using an integrative approach coupling field-based study and hydrodynamic modeling[END_REF]. Levels of nonylphenol and octylphenol in other Asian countries are also high, with nonylphenol as high as 1100 ng/L in seawater in Tokyo Bay, Japan [START_REF] Song | Field survey of environmental estrogen pollution in the coastal area of Tokyo Bay and Nagasaki City using the Japanese common goby Acanthogobius flavimanus[END_REF]. Levels of nonylphenol and octylphenol in European countries are much lower, with the highest concentration reported in pond sediments in Greece being 323 ng/g for nonylphenol [START_REF] Bokony | Endocrine disruptors in breeding ponds and reproductive health of toads in agricultural, urban and natural landscapes[END_REF]. Limited data are available for countries in Africa and North and South America (Table 1.2). The presence of other alkylphenols has hardly been reported. [START_REF] Liu | Occurrence, distribution, and risk assessment of alkylphenols, bisphenol A, and tetrabromobisphenol A in surface water, suspended particulate matter, and sediment in Taihu Lake and its tributaries[END_REF] reported levels of 4-tert-butylphenol, 2,4-di-tert-pentylphenol, 4-n-heptylphenol, 4-butylphenol, and 4-n-hexylphenol in surface waters, suspended particulates, and sediment in Lake Taihu and its tributaries in China, and their concentrations were lower than those of nonylphenol and octylphenol. [START_REF] Saeed | Sources and levels of endocrine disrupting compounds (EDCs) in Kuwait's coastal areas[END_REF] reported C4-C9 alkylphenols in coastal waters and sediments in Kuwait, with concentrations of ng/L and subng/L in water and ng/g and subng/g in sediments, respectively.

Environmental Fate Adsorption of alkylphenol to solid particles (sediment and suspended solids) and organic matter is a critical process that dominates their fate, transport, bioavailability and toxicity in the aquatic environment. [START_REF] Hu | Occurrence, behavior and risk assessment of estrogens in surface water and sediments from Hanjiang River, Central China[END_REF] reported that log K OC values of nonylphenol and octylphenol calculated under field conditions were 4.63-4.78 and 4.74-4.84, respectively, indicating their high affinity for organic matter. [START_REF] Gong | Seasonal variation and partitioning of endocrine disrupting chemicals in waters and sediments of the Pearl River system, South China[END_REF] found that in the Pearl River system in South China, log K OC values for nonylphenol in suspended particulate matter and sediment were 5.05 ± 0.33 and 4.59 ± 0.26, respectively. The corresponding values for octylphenol were 4.89 ± 0.41 and 4.32 ± 0.49, respectively. Biodegradation is another major factor in the fate of alkylphenols in the aquatic environment. Fate modeling in the Yong River in China indicated that the contribution of adsorption was greater than that of biodegradation, while the opposite was true for 4-t-octylphenol [START_REF] Cheng | Distribution and fate modeling of 4-nonylphenol, 4-t-octylphenol, and bisphenol A in the Yong River of China[END_REF]). The half-lives for nonylphenol in estuarine waters alone and estuarine waters with sediment would be 2.36 ± 1.76 and 1.31 ± 0.51 d [START_REF] Yang | Contributions of abiotic and biotic processes to the aerobic removal of phenolic endocrine-disrupting chemicals in a simulated estuarine aquatic environment[END_REF]).

Another study showed that the half-lives of nonylphenol in the water/sediment system under several redox conditions, ranging from aerobic to sulfate reduction, ranged from 3.2 to 6.2 d [START_REF] Koumaki | Assessment of the environmental fate of endocrine disrupting chemicals in rivers[END_REF]. A variety of bacteria, fungi and microalgae have been found to degrade alkylphenols. The consortium of cyanobacteria Arthrospira Maxima and the green microalgae Chlorella vulgaris can remove 96% of 4-nonylphenol from water in 96 h [START_REF] Zaytseva | Sorption and biodegradation of octyl-and nonylphenols by the cyanobacterium Planktothrix agardhii (Gomont) Anagn. & Komarek[END_REF]. Other microalgae can also remove nonylphenol to varying degrees (He et al. 2016). Fungi of the genera Aspergillus and Penicillium have been found to effectively degrade 4-n-nonylphenol within a few days (Zhang et al. 2016a;[START_REF] Yang | Different pathways for 4-n-nonylphenol biodegradation by two Aspergillus strains derived from estuary sediment: evidence from metabolites determination and key-gene identification[END_REF]). It should be noted that the biodegradation of nonylphenol is isomer-specific and affected greatly by the redox potential; for example, the half-lives of 19 nonylphenol isomers in oxic river sediments ranged from 0.9 to 13.2 d (Lu and Gan 2014a). Biodegradation pathways of 4-nonylphenol include ipso-hydroxylation in the para position, nitrification at the ortho-position, and oxidation of the alkyl-chain, in particular ω-oxidation and then β-oxidation of the nonyl chain when fungi are involved. However, the routes of action of 4-n-nonylphenol are different. One pathway is initiated by hydroxylation at the terminal β-carbon atom, followed by oxidation and decarboxylation. Another pathway is initiated by hydroxylation at the orthopositions and followed by ring-opening reactions (Zhang et al. 2016a;[START_REF] Yang | Different pathways for 4-n-nonylphenol biodegradation by two Aspergillus strains derived from estuary sediment: evidence from metabolites determination and key-gene identification[END_REF].

Toxicity The estrogenicity of nonylphenol and octylphenol has been known for decades and has been confirmed in fish (Ahmadpanah et 2016) also reported that the reproductive capacity of Cichlasoma dimerus caused by 4-t-octylphenol could be recovered when transferred to octylphenol-free water. Exposure to nonylphenol may increase vitellogenin and vitellogenin receptor expression in the shrimp Macrobrachium rosenbergii (Guo et al. 2019), weaken the immune system of the Pacific oyster Crassostrea gigas [START_REF] Hart | Effect of 4-nonylphenol on the immune response of the Pacific oyster Crassostrea gigas following bacterial infection with Vibrio campbellii[END_REF], reduce the biomass of mussels (Lampsilis siliquoidea and Villosa iris) [START_REF] Ivey | Chronic toxicity of 4-nonylphenol to two unionid mussels in water-only exposures[END_REF], and disrupt lipid storage [START_REF] Jordao | Compounds altering fat storage in Daphnia magna[END_REF], moulting, and reproduction of the water flea Daphnia magna [START_REF] Kim | Evaluation of 4-nonylphenol and bisphenol A toxicity using multiple molecular biomarkers in the water flea Daphnia magna[END_REF]. Nonylphenol and octylphenol can also induce oxidative responses in algae such as Gracilaria lemaneiformis [START_REF] Zhong | Toxic effect of nonylphenol on the marine macroalgae Gracilaria lemaneiformis (Gracilariales, Rhodophyta): antioxidant system and antitumor activity[END_REF]) and Dictyosphaerium sp. [START_REF] Cheng | Bioaccumulation, growth performance, and transcriptomic response of Dictyosphaerium sp. after exposure to nonylphenol[END_REF]) and the submersed macrophyte Ceratophyllum demersum [START_REF] Cahyanurani | Glutathione biosynthesis plays an important role against 4-tert-octylphenol-induced oxidative stress in Ceratophyllum demersum[END_REF]. The Yeast Estrogen Screen Test, the Two Hybrid Yeast Test, the MVLN Cell Test and the E-Screen Test all showed that the estrogenicity of nonylphenol was isomer-specific (Lu and Gan 2014a). However, no studies were conducted in aquatic species. The co-existence of other pollutants may increase or decrease the toxicity of alkylphenols to aquatic species. The equitoxic mixture of copper and nonylphenol was antagonistic to the embryos and larvae of Rhinella arenarum toad at LC50 [START_REF] Aronzon | Mixture toxicity of copper and nonylphenol on the embryolarval development of Rhinella arenarum[END_REF]. [START_REF] Carnevali | Dietary administration of EDC mixtures: a focus on fish lipid metabolism[END_REF] demonstrated that dietary intake of bisphenol A, octylphenol, and nonylphenol by juvenile sea bream was antagonistic to its lipid metabolism. However, Cd(II) enhanced growth inhibition and superoxide induction in the alga Chlorella sorokiniana (Wang et al. 2018a). All these results suggest that further research is needed on the co-toxicity of nonylphenol and other pollutants.

Environmental Impact of Rare Earth Elements

Rare earth elements (REEs) are a group of 17 elements (fifteen lanthanides as well as yttrium and scandium) that tend to occur in the same ore deposits in Nature and exhibit similar physical and chemical properties. One of the members of the lanthanide series, promethium (Pm) which has only radioactive isotopes is usually recovered from the leftovers of uranium fission. Rare earth elements occur at trace concentration levels in the upper continental crust with total content ranging from <1 to 65μg/g (Table 1.3). These are highly electropositive and normally exists predominantly in trivalent stage (M 3+ ), with the exception of cerium which exists in quadrivalent valent state (Ce 4+ ) and europium which exists in divalent state (Eu 2+ ) under oxidizing and reducing environments respectively [START_REF] Balaram | Recent trends in the instrumental analysis of rare earth elements in geological and industrial materials[END_REF]. Their unique electronic, optical, magnetic, and catalytic properties give them the ability to donate and accept electrons, making them suitable for integral components of many hi-tech products such as mobile phones, computers, home entertainment, medical devices, military defense systems, autocatalytic converters, petroleum refining and for polishing of optical-quality glass, and emerging clean energies. Thus, their industrial applications can be divided mainly into catalysts, ceramics, metallurgy, polishing and other applications (Fig. 1.5). A number of reviews has been published in recent times on all aspects of rare earth elements including their applications, occurrence, exploration, and their chemical analysis (e.g., [START_REF] Mubashir | Rare earth elements -a review[END_REF][START_REF] Balaram | Rare earth elements: a review of applications, occurrence, exploration, analysis, recycling, and environmental impact[END_REF]. The extensive applications of these elements have led to their wide distribution in all environmental compartments, raising concerns over their potential effects on human health. Because of well-known toxic effects of elements such as As, Cd, Pb, Hg and U, most of the environmental toxicity studies so far have been confined to this set of elements only (e.g., [START_REF] Sparks | Toxic metals in the environment: the role of surfaces[END_REF][START_REF] Reddy | Assessment of the effects of municipal sewage, immersed idols and boating on the heavy metal and other elemental pollution of surface water of the eutrophic Hussainsagar Lake (Hyderabad, India)[END_REF][START_REF] Duggal | Risk assessment of metals from groundwater in Northeast Rajasthan[END_REF]. Even platinum group elements have received considerable attention in recent years for their impact on human health due to their extensive utilization in autocatalysts [START_REF] Balaram | Environmental impact of Pt, Pd and Rh emissions from autocatalytic converters -a brief review of the latest developments[END_REF]. But in recent times, technological innovations coupled to modern living conditions have been contributing to the enhancing intake of significant quantities of rare earth elements by humans. Several studies demonstrated that these elements have toxic effects on human health and therefore are considered as emerging pollutants (e.g., [START_REF] Pagano | Health effects and toxicity mechanisms of rare earth elements-knowledge gaps and research prospects[END_REF][START_REF] Rim | Effects of rare earth elements on the environment and human health: a literature review[END_REF]). These elements can accumulate in the different environmental compartments and also in the biota, by many different routes such as mining, mineral processing, e-waste, agriculture practices, medicines and rudimentary recycling and disposal practices. Impact of Rare Earth Elements Mining Though its more than a century since commercial mining of rare earth elements started, their global production and consumption have seen a significant increase during last half century, thus currently posing mounting environmental risk. Intense rare earth elements mining and production activities have led to significant environmental and health impacts already in countries such as China, US, India, Malaysia and Brazil. There are a number of potential environmental implications to mining of rare earth elements if not done properly. Mining activities such as cutting, drilling, blasting, transportation, stockpiling, and processing can release dust containing rare earth elements, other toxic metals and chemicals into air and surrounding water bodies that can impact local soil, vegetation, wildlife, and humans. Some of the rare earth element minerals contain significant amounts of radioactive elements such as uranium and thorium, which can contaminate air, soil, surface water and groundwater [START_REF] Balaram | Rare earth elements: a review of applications, occurrence, exploration, analysis, recycling, and environmental impact[END_REF].

According to [START_REF] Hurst | China's rare earth elements industry: what we can the west learn? Department of Defense[END_REF], approximately one ton of calcined rare earth ore generates 9600-12,000 cubic meters of waste gas containing dust concentrate, hydrofluoric acid, sulfur dioxide, and sulfuric acid, approximately 75 cubic meters of acidic wastewater, and about one ton of radioactive waste residue containing water. Most of that wastewater is normally discharged without being effectively treated, which can not only contaminate potable water for daily living of the neighboring communities, but also contaminates the surrounding water environment and irrigated farmlands. For example, an urban street dust of an industrial city, Zhuzhou in central China recorded very significant concentrations of rare earth elements (ΣREEs ranged from 66.1 to 237.4μg/g with an average of 115.9μg/g) which reveals the gravity of the rare earth elements pollution, particularly in industrial cities [START_REF] Sun | Rare earth elements in street dust and associated health risk[END_REF]). More mining of rare earth elements, however, will mean more environmental degradation and human health hazards as waste disposal areas can be exposed to weathering conditions and have the potential to pollute the air, soil and water if adequate monitoring and protection measures are not applied [START_REF] Barakos | A forward look into the US rare-earth industry. How potential mines can connect to the global REE market?[END_REF]). These problems are due to insufficient environmental regulations and controls in the mining and processing areas in different countries.

Rare Earth

Elements in e-Waste Toxic metals are increasingly present in water systems around the World due to human activities, such as unregulated mining and more recently, the inadequate disposal of electronic waste. Dumping of huge amounts of e-waste that facilitate the release of significant quantities of rare earth elements along with several other toxic elements is leading to severe contamination of the subsoils and ground water [START_REF] Haxel | Rare earth elements -critical resources for high technology[END_REF]. Each year, the electronics industry generates up to 50 million tons of e-waste, but as the number of consumers rises, and the lifespan of devices shrinks in response to demand for the updated equipment, this figure could cross 50 million tons in the coming years. Rare earth elements are known to be more mobile in solutions rich in F -, Cl -, HCO 3 -, CO 3 2-, HPO 4 2-, PO 4 3-ions [START_REF] Xiong | The mobility of rare-earth elements during hydrothermal activity: a review[END_REF]. In addition, large quantities of rare earth elements are also getting into the agricultural soils through the phosphatebased fertilizers (Table 1.3). Under natural conditions, rare earth elements may become available only in small amounts via the groundwater and the atmosphere; however, their increased use and enhanced amounts have created several new routes for bioaccumulation (in plants, animals, and human beings). Background level of rare earth elements content in waters, both surface and subsoil, varies significantly and depends mostly on the local geology.

Recycling of Rare Earth Elements

Recycling and recovering activities of the valuable rare earth elements found in advanced electronic gadgets such as mobile phones, smart television sets, magnets, computers, batteries and catalysts, have been a challenge for both manufacturers and environmental groups. Several research groups are involved in the developments of technologies that could recover these materials for reuse [START_REF] Hasegawa | Chelatorinduced recovery of rare earths from end-of-life fluorescent lamps with the aid of mechanochemical energy[END_REF][START_REF] Jowitt | Recycling of the rare earth elements[END_REF]. The intensity of this activity is driven by the demand for these elements and its future potential and sustainability requires a significant amount of research on these aspects. One of the biggest electronic companies, Apple has already started expanding the company's global recycling programs [START_REF] Balaram | Rare earth elements: a review of applications, occurrence, exploration, analysis, recycling, and environmental impact[END_REF]. Increasing the amount of rare earth elements recycling may contribute to overcoming some of the criticality issues related to the supply of these elements. However, recycling activities such as the treatment of raw materials, beneficiation, separation of rare earth elements as oxides and their purification can also contribute to the release of substantial amounts of these metals into the environment.

Adverse Effects of the Use of Rare Earth Elements in Agriculture Rare earth elements containing micro fertilizers are extensively utilized in agriculture because of the striking positive effects in terms of crop yield and quality [START_REF] Hu | Rare earth elements in soils[END_REF], therefore leading to further increase in the concentrations of these elements in soils [START_REF] Guo | Rare earths in agriculture[END_REF][START_REF] Diatloff | Rare earth elements and plant growth-third responses of corn and mungbean to low concentrations of cerium in dilution, continuously flowing nutrient solutions[END_REF]. Although several findings reported positive effects of rare earth elements on plant growth, many questions about their biological role remain unclear. Their concentrations in vegetables produced from mining area are higher and can have health implications especially in children [START_REF] Zhuang | Concentrations and health risk assessment of rare earth elements in vegetables from mining area in Shandong, China[END_REF]. In general, the mineral fertilizers (i.e., phosphate fertilizers) and soil conditioners contain macronutrients (Ca, Mg, N, P, and S), micronutrients (such as Fe and Si) and rare earth elements. In soils, the rare earth elements can also originate from local geological parent materials [START_REF] Liu | The effects of rare earth elements on growth of crops V[END_REF]. Although the accumulated concentrations of rare earth elements have been reported to be very low, the accumulation capacity of a particular plant depends upon several factors such as plant species, their growing conditions and the rare earth elements content in the substrate soil or rock [START_REF] Fu | The variation of REE (rare earth elements) patterns in soil-grown plants: a new proxy for the source of rare earth elements and silicon in plants[END_REF]). Table 1.3 presents the concentrations of rare earth element in different parts of plants such as roots, stem and leaves of a particular plant species, which can give an idea on how these elements can reach biota. Following excessive application of rare earth elements in agriculture, there is a raising environmental concern that these elements may enter the food chain in greater quantities though plant uptake, which might be deleterious to human health. For instance, the studies conducted by [START_REF] Redling | Rare earth elements in agriculture with emphasis on animal husbandry[END_REF] confirmed very low concentrations of rare earth elements in cereal grains and no significant accumulation due to rare earth elements fertilization. Thus, grains and products made of them such as wheat flour are considered to be safe. [START_REF] Thomas | Rare earth elements (REE): effects on germination and growth of selected crop and native plant species[END_REF] have indicated that countries like Russia and Nigeria where the natural abundance levels of rare earth elements are high in their soils will have more environmental threats arising from the increased input of these elements. However, close monitoring may be needed in countries where phosphate-based fertilizers (mined from monazite deposits) are applied in large scale.

Rare Earth Elements in Medicine

Their unique properties, such as radiation emission and magnetism, allow these elements to be used in many health and medical applications, such as in anti-tumor agent, kidney dialysis medicine and surgical equipment [START_REF] Giese | Rare earth elements: therapeutic and diagnostic applications in modern medicine[END_REF]. Though, there are currently a few major applications of rare earth elements in medicine and many others are on the horizon [START_REF] Lu | Realizing the therapeutic potential of rare earth elements in designing nanoparticles to target and treat glioblastoma[END_REF]).

Lanthanide compounds with outstanding stability (photo-and redox-stability) and luminescent properties have found wider applications in cancer therapy and imaging [START_REF] Teo | Lanthanides: applications in cancer diagnosis and therapy[END_REF]. For example, Gadolinium has been used in a chelated form as a contrast agent in magnetic resonance imaging measurements [START_REF] Raju | Speciation of gadolinium-based MRI contrast agents in environmental water samples using hydrophilic interaction chromatography hyphenated with inductively coupled plasma mass spectrometry[END_REF].

Even the pharmaceutical samples analyzed for inorganic impurities are found to contain appreciable amounts of rare earth elements when analyzed by inductively coupled plasma mass spectrometry (ICP-MS) [START_REF] Balaram | Recent advances in the determination of elemental impurities in pharmaceuticals e status, challenges and moving frontiers[END_REF]. The implications of the presence of this range of rare earth elements concentrations in pharmaceuticals, are not clear at present. On one hand, rare earth elements have been found to diseasecausing and occupational poisoning of local residents in mining areas, water pollution, and farmland destruction, etc. A body of evidence; has shown that rare earth elements are associated with antioxidant properties that are used in the treatment of many diseases [START_REF] Rim | Effects of rare earth elements on the environment and human health: a literature review[END_REF]. Several studies [START_REF] Zhang | Effect of Lanthanum on growth and biochemical property of Sclerotinia sclerotiorum[END_REF][START_REF] Wakabayashi | Antibacterial, antifungal and nematicidal activities of rare earths ions[END_REF]) confirmed the antibacterial and antifungal activities of rare earth elements that are comparable to those of copper ions, and thus these elements are starting to be used for several pharmaceutical applications. Rare earth elements can also be used as nematicide as they can also inhibit the formation and germination of fungal spores and thus influence large number of organisms [START_REF] Zhang | Effect of Lanthanum on growth and biochemical property of Sclerotinia sclerotiorum[END_REF]. Recently, the medical and biological properties of rare earth elements have been reviewed by [START_REF] Panichev | Rare earth elements: review of medical and biological properties and their abundance in the rock materials and mineralized spring waters in the context of animal and human geophagia reasons evaluation[END_REF]. New medical applications for these elements are being found at an increasing rate and emerging advancements such as nanotechnology might be used to enhance their use in medicine in the future.

Health Effects to Humans Extensive mining activities and dumping of huge amounts of e-waste are facilitating release of significant quantities rare earth elements along with several other toxic elements and radionuclides into the subsoils and ground water. In addition, the largescale application of rare earth elements in various modern technologies is continually growing despite the knowledge about the environmental concerns of these elements. In addition, there is also a widespread use of these elements in agriculture and medicine sectors [START_REF] Xiong | The mobility of rare-earth elements during hydrothermal activity: a review[END_REF]. As a result, large quantities of rare earth elements are also getting migrated into the agricultural soils, groundwater and thereby food products. Unfortunately, there is no sufficient data available about the toxicity of rare earth elements to human health and thus, their maximum acceptable limits in drinking water were not provided yet by any international health organization. [START_REF] Sneller | Maximum permissible concentrations and negligible concentrations for rare earth elements (REES)[END_REF] have reported maximum permissible concentrations for different rare earth elements in drinking water and the validity of these values is not known (Table 1.3). Currently, there are substantial gaps in our understanding of the adverse effects of rare earth elements to human health, their anthropogenic levels and fate, their biogeochemical or anthropogenic cycling, and their individual and additive toxicological effects. Most of the harmful effects resulting from human exposure to rare earth elements exposure are reported in occupational studies of mine workers and others who regularly deal with rare earth elements or their products, where exposure is typically much higher than that which the general population would experience. There are also several reports of occupational exposure to rare earth elements that resulted in bioaccumulation and adverse effects to human health [START_REF] Mcdonald | Intracranial gadolinium deposition after contrast-enhanced MR imaging[END_REF][START_REF] Yoon | Dendriform pulmonary ossification in a patient with rare earth pneumoconiosis[END_REF][START_REF] Giovanni | Rare earth elements in human and environmental health. At the crossroads between toxicity and safety[END_REF][START_REF] Rim | Effects of rare earth elements on the environment and human health: a literature review[END_REF]. More studies are required to identify various anthropogenic sources, transfer mechanisms, bioaccumulation and their environmental behavior to minimize human health risks in future.

Despite substantial increase in the number of studies, many questions about the environmental and biological effects of rare earth elements remain unanswered. As the use of rare earth elements in industrial, agricultural and health applications is expected to increase to a great extent in the future, risk assessment studies on the daily intake of rare earth elements through dust, air, water and food, and on the subsequent long-term health effects on humans including pregnant women, children, and other vulnerable populations, have to be speeded up. In order to fill in the current gaps in our understanding of the roles of different rare earth elements, multifaceted studies focusing on different organisms and exposure routes are needed. As the mining, processing and recycling of rare earth elements will be imperative in the future in order to meet the demand for these elements, it is necessary to formulate verified guidelines and monitoring systems to guarantee the welfare of workers, but also to protect the environment in general.

Engineered Nanoparticles in Drinking Waters Sources

In the last decade, nanotechnology has brought a large number of nanoparticles, engineered nanoparticles and nanomaterials to applications in multiple daily products and for many industrial products, due to their specific physicochemical properties [START_REF] Mueller | Exposure modeling of engineered nanoparticles in the nnvironment[END_REF][START_REF] Gottschalk | The release of engineered nanomaterials to the environment[END_REF]. For example, titanium dioxide and zinc oxide nanoparticles can be found in sunscreens and cosmetics [START_REF] Lu | Analysis of titanium dioxide and zinc oxide nanoparticles in cosmetics[END_REF]; titanium dioxide, silver, and silicon dioxide in paints and coatings [START_REF] Hanus | Nanotechnology innovations for the construction industry[END_REF]; silver nanoparticles in textiles due to their antimicrobial properties [START_REF] Hardin | Nanotechnology for antimicrobial textiles (chapter 6)[END_REF]; cerium oxide nanoparticles as fuel additives [START_REF] Dale | Transformation of cerium oxide nanoparticles from a diesel fuel additive during combustion in a diesel engine[END_REF]); C60-fullerenes in dermatological and skin care products [START_REF] Mousavi | Fullerene nanoparticle in dermatological and cosmetic applications[END_REF]; or carbon nanotubes as nanofertilizers [START_REF] Iavicoli | Nanotechnology in agriculture: opportunities, toxicological implications, and occupational risks[END_REF]. This increase in use of engineered nanoparticles ends up in waste streams, and consequently in the environment and drinking water resources. The potential human risks from engineered nanoparticles in drinking water are still unknown and uncertain, due to the limited data on the occurrence and toxicity of nanoparticles in waters [START_REF] Good | Implications of engineered nanomaterials in drinking water sources[END_REF]Bhattacharyya et al. 2017a, b). Potential impacts on the environment and human health have been reported [START_REF] Born | The potential risks of nanomaterials: a review carried out for ECETOC[END_REF][START_REF] Biskos | Airborne engineered nanoparticles: potential risks and monitoring challenges for assessing their impacts on children[END_REF].

According to [START_REF] Gottschalk | The release of engineered nanomaterials to the environment[END_REF], engineered nanoparticles may enter into the environment through production, incorporation of nanoparticles into products, the use of nanoparticles containing products, and through wastewater treatment plants, waste incineration, landfills, and recycling and disposal processes. In addition, during their life cycle, the characteristics of engineered nanoparticles can change (due to physical/chemical interactions such as agglomeration, dissolution), as well as aging/degradation of the nanoparticles or nanoparticles containing products [START_REF] Gottschalk | The release of engineered nanomaterials to the environment[END_REF]. Surface water, such as lakes, rivers and streams, may therefore receive engineered nanoparticles, which may represent a threat to human health if this water is used for human consumption. In developed countries, 80% of the water supply is from surface water, while smaller communities or private residences are supplied by groundwater [START_REF] Westerhoff | Low risk posed by engineered and incidental nanoparticles in drinking water[END_REF].

Occurrence in Surface Waters Surface waters have many sources of engineered nanoparticles, including natural, unintentional and intentional sources [START_REF] Hochella | Nanominerals, mineral nanoparticles, and earth systems[END_REF][START_REF] Park | Occurrence and removal of engineered nanoparticles in drinking water treatment and wastewater treatment processes[END_REF]. Natural sources such as mineral weathering, sea spray, volcanoes and forest fires also include nanoparticles beyond other particle sizes [START_REF] Hochella | Nanominerals, mineral nanoparticles, and earth systems[END_REF]. Unintentional release usually includes non-point sources and release from products such as cosmetics (e.g., sunscreens, [START_REF] Weir | Titanium dioxide nanoparticles in food and personal care products[END_REF], wearing or washing textiles containing engineered nanoparticles [START_REF] Gottschalk | The release of engineered nanomaterials to the environment[END_REF], paints [START_REF] Mueller | Exposure modeling of engineered nanoparticles in the nnvironment[END_REF], urban runoff [START_REF] Baalousha | Outdoor urban nanomaterials: the emergence of a new, integrated, and critical field of study[END_REF], or combustion, wear and corrosion processes [START_REF] Westerhoff | Low risk posed by engineered and incidental nanoparticles in drinking water[END_REF]. However, major incidental engineered nanoparticles releases into the environment occur via wastewater treatment for cosmetics, coatings, cleaning agents, and dietary supplements [START_REF] Gottschalk | Modeled environmental concentrations of engineered nanomaterials (TiO 2 , ZnO, Ag, CNT, Fullerenes) for different regions[END_REF]. Intentional sources are usually related with the application of the engineered nanoparticles directly, for example, when used in drinking water or wastewater treatments [START_REF] Brar | Engineered nanoparticles in wastewater and wastewater sludge -evidence and impacts[END_REF], in remediation of contaminated sites because of their sorption capacities [START_REF] Nowack | Occurrence, behavior and effects of nanoparticles in the environment[END_REF] or applied as agrochemicals and nanopesticides [START_REF] Kah | Nanopesticide research: current trends and future priorities[END_REF][START_REF] Iavicoli | Nanotechnology in agriculture: opportunities, toxicological implications, and occupational risks[END_REF]. Groundwater may also receive engineered nanoparticles through direct use, e.g., nano zero-valent iron injected into groundwater contaminated with chlorinated solvents then directly pumped into the subsurface [START_REF] Nowack | Occurrence, behavior and effects of nanoparticles in the environment[END_REF][START_REF] Grieger | Environmental benefits and risks of zero-valent iron nanoparticles (nZVI) for in situ remediation: risk mitigation or trade-off?[END_REF]. Carbon nanotubes are intentionally loaded in water and soil to detect, prevent or remove pollutants [START_REF] Mauter | Environmental applications of carbon-based nanomaterials[END_REF].

Once released into water, engineered nanoparticles can undergo various transformations, including degradation, agglomeration, dissolution and sedimentation, and their fate, mobility, and persistence in aquatic systems are largely dependent on these transformations and their stability [START_REF] Nowack | Occurrence, behavior and effects of nanoparticles in the environment[END_REF]. Thus, the significance of engineered nanoparticles to drinking water supplies depends upon their stability and mobility in water resources used for drinking water production, which is largely determined by engineered nanoparticles colloidal stability. Engineered nanoparticles have high surface energies, due to their high surface-to-volume ratios, so they tend to aggregate [START_REF] Hu | Effect of dissolved organic matter on the stability of magnetite nanoparticles under different pH and ionic strength conditions[END_REF][START_REF] Sousa | Aggregation kinetics and surface charge of CuO nanoparticles: the influence of pH, ionic strength and humic acids[END_REF][START_REF] Sousa | The effect of TiO 2 nanoparticles removal on drinking water quality produced by conventional treatment C/F/S[END_REF]. Furthermore, if repulsive electrostatic forces are dominant, an increase in ionic strength leads to reduced engineered nanoparticle stability and an increase in aggregation [START_REF] Chen | Aggregation and deposition kinetics of fullerene (C60) nanoparticles[END_REF][START_REF] Li | Aggregation and dissolution of silver nanoparticles in natural surface water[END_REF][START_REF] Sousa | Aggregation kinetics and surface charge of CuO nanoparticles: the influence of pH, ionic strength and humic acids[END_REF]. However, aggregation rate stops increasing with ionic strength because each collision leads to attachment and aggregation becomes diffusion-limited, at a particular electrolyte concentration known as the critical coagulation concentration [START_REF] Troester | Vulnerability of drinking water supplies to engineered nanoparticles[END_REF]. However, at Na + and Ca 2+ concentrations typically found in surface waters, destabilization of engineered nanoparticles by Na + and Ca 2+ is, respectively, too low or limited [START_REF] Troester | Vulnerability of drinking water supplies to engineered nanoparticles[END_REF]. The naturally occurring organic matter present in surface waters can interact with engineered nanoparticles and influence suspension stability. Organic matter surface coating of engineered nanoparticles influences the aggregation rate of particles by electrostatic stabilisation mechanisms and electrosteric repulsion [START_REF] Chen | Influence of humic acid on the aggregation kinetics of fullerene (C60) nanoparticles in monovalent and divalent electrolyte solutions[END_REF][START_REF] Baalousha | Aggregation and surface properties of iron oxide nanoparticles: influence of pH and natural organic matter[END_REF][START_REF] Klaine | Nanomaterials in the environment: behavior, fate, bioavailability, and effects[END_REF][START_REF] Sousa | Aggregation kinetics and surface charge of CuO nanoparticles: the influence of pH, ionic strength and humic acids[END_REF]. The extent of the stabilization is dependent of organic matter type and concentration [START_REF] Chen | Influence of humic acid on the aggregation kinetics of fullerene (C60) nanoparticles in monovalent and divalent electrolyte solutions[END_REF][START_REF] Sousa | Aggregation kinetics and surface charge of CuO nanoparticles: the influence of pH, ionic strength and humic acids[END_REF][START_REF] Zhang | Effects of humic and fulvic acids on aggregation of aqu/nC60 nanoparticles[END_REF]. [START_REF] Baalousha | Aggregation and disaggregation of iron oxide nanoparticles: influence of particle concentration, pH and natural organic matter[END_REF] referred that an increase of nanoparticle concentration enhances their aggregation, particularly at pH values close to the engineering nanoparticle isoelectric points. In addition, at pH equal to the engineering nanoparticle isoelectric point, particles have little or no charge, leading to a substantial weakening in the repulsive forces between nanoparticles and aggregation occurs [START_REF] Baalousha | Aggregation and disaggregation of iron oxide nanoparticles: influence of particle concentration, pH and natural organic matter[END_REF]. For surface waters pHs, between 6.5 and 8.5, only limited electrostatic stabilization can be expected for bare cerium oxide and bare iron oxide nanoparticles, since their isoelectric points are reported within this range [START_REF] Illés | The effect of humic acid adsorption on pH-dependent surface charging and aggregation of magnetite nanoparticles[END_REF][START_REF] Baalousha | Aggregation and surface properties of iron oxide nanoparticles: influence of pH and natural organic matter[END_REF][START_REF] Zhang | Stability of commercial metal oxide nanoparticles in water[END_REF].

In a very simplified way, [START_REF] Hammes | Geographically distributed classification of surface water chemical parameters influencing fate and behavior of nanoparticles and colloid facilitated contaminant transport[END_REF] evaluated the effects of the physicochemical properties of the water on the ultimate fate of nanoparticles and contaminant-colloid assemblies across Europe. These authors showed more stable conditions for contaminant-colloid assemblies in northern Europe, the alpine region and Austria, Scotland, Northern Ireland and on the north-western Iberian Peninsula. In addition, as sedimentation rates were expected to be low in these areas, they concluded that aquatic organisms may be exposed to higher to small sized nanoparticle compared to waters in Italy, southern Portugal and Spain, France, Germany, east England and eastern Europe where conditions to nanoparticle aggregate prevail.

Predicted and Measured Engineered Nanoparticles Concentrations in Surface

Waters Data available on the occurrence and quantities of engineered nanoparticles in surface waters are scarce. The uncertainties about the input and production quantities, the multiple pathways for engineered nanoparticles entering into the environment, but mostly the absence of widespread adequate detection techniques for identifying low concentrations of engineered nanoparticles in natural waters contribute to these limited data (von der [START_REF] Der Kammer | Analysis of engineered nanomaterials in complex matrices (environment and biota): general considerations and conceptual case studies[END_REF][START_REF] Westerhoff | Low risk posed by engineered and incidental nanoparticles in drinking water[END_REF]). Rather models have been developed to predict engineered nanoparticles concentrations. [START_REF] Gottschalk | Environmental concentrations of engineered nanomaterials: review of modeling and analytical studies[END_REF] reviewed published data on the distribution of engineered nanoparticles in surface waters, both modelled and experimental data. [START_REF] Troester | Vulnerability of drinking water supplies to engineered nanoparticles[END_REF] made an actualisation of that review. According to [START_REF] Gottschalk | Environmental concentrations of engineered nanomaterials: review of modeling and analytical studies[END_REF], modelled nano-titanium dioxide concentrations in rivers ranged from 0.003 to 1.6μg/L, at high temporal and geographical resolution, and this range included other modelled concentration ranges. Nano-silver presented high variations between the highest and lowest values, approximately a factor of 1x10 5 for the difference, which might reflect the differences between initial estimates of nanosilver production [START_REF] Gottschalk | Environmental concentrations of engineered nanomaterials: review of modeling and analytical studies[END_REF]. Modelled nano-zinc oxide varied between ca. 1 × 10 -4 and 1 × 10 -1 μg/L, but only two studies have reported concentrations in aqueous systems; carbon nanotube varied between 1 × 10 -5 and 1 × 10 -3 μg/L; fullerenes ranged from 1 × 10 -5 to 1 × 10 -4 μg/L; and cerium oxide nanoparticles were in the range 1 × 10 -2 to 1 × 10 -1 μg/L [START_REF] Gottschalk | Environmental concentrations of engineered nanomaterials: review of modeling and analytical studies[END_REF]. More recent modelling studies revised in by [START_REF] Troester | Vulnerability of drinking water supplies to engineered nanoparticles[END_REF], showed concentrations ranging for titanium dioxide nanoparticles between 0.40 and 1.4 μg/L; for silver nanoparticles between 0.51 ng/L and 0.94 ng/L; for zinc oxide nanoparticles between 0.05 ng/L and 0.29μg/L; for C60 between 0.07 ng/L and 0.28 ng/L; and for carbon nanotubes between 0.17 ng/L and 0.35 ng/L for percentile 15 and 85%, respectively [START_REF] Sun | Comprehensive probabilistic modelling of environmental emissions of engineered nanomaterials[END_REF]). In addition, some studies predicted engineered nanoparticles concentrations at different distances from emission source, showing a decrease in concentrations justified by hetero-aggregation and sedimentation of the engineered nanoparticles [START_REF] Troester | Vulnerability of drinking water supplies to engineered nanoparticles[END_REF]. Experimental studies revealed similar concentrations of nano-titanium dioxide from the ones predicted [START_REF] Gottschalk | Environmental concentrations of engineered nanomaterials: review of modeling and analytical studies[END_REF][START_REF] Troester | Vulnerability of drinking water supplies to engineered nanoparticles[END_REF]. Table 1.4 presents an overview of recent published data on measured engineered nanoparticles in surface waters that are dependent on the nanoparticles type and ranges within with the ealier studies presented in the table. Some studies demonstrate a remarkable decrease in measured engineered nanoparticles concentration with the distance of the point source, namely wastewater treatment plants [START_REF] Syafiuddin | Silver nanoparticles in the water environment in Malaysia: inspection, characterization, removal, modeling, and future perspective[END_REF][START_REF] Wimmer | Silver nanoparticle levels in river water: real environmental measurements and modeling approaches -a comparative study[END_REF].

The data currently available suggest that engineered nanoparticles may be present in certain surface waters, but not at high concentrations. However, the amount of analytical data available remains too small. There is a continuing need to detect and quantify these emerging contaminants in water. The low concentrations result from the removal mechanisms occurring in surface waters, particularly in waters with moderate or high ionic strengths, and organic matter high concentrations. Nevertheless, an expected increase of engineered nanoparticles production and use might increase the concentration of engineered nanoparticles in surface waters and the risk of water contamination. Furthermore, localized high-input sources may exist and engineered nanoparticle releases that may impact drinking water treatment plants intake should be carefully analysed and monitored.

Substances of Emerging Global Concern

Persistent Organic Pollutants in Lake and Ocean Ecosystems

The term "persistent organic pollutant" describes a wide range of organic compounds of anthropogenic origin present in the environment. This family of substances is subdivided into four main categories, namely polycyclic aromatic hydrocarbons (PAHs), chlorinated aromatic compounds, pesticides (organochlorine pesticides) and brominated flame retardants. The best known substances are, for example, 2,4-dichlorophenoxyacetic acid herbicide (well known as 2,4-D), hexachlorobenzene (another chlorinated fungicide used to treat seeds, especially wheat), polychlorinated biphenyls commonly known as PCBs used as lubricants in transformers, or PAHs from combustion or pyrolysis. The list of substances is particularly long due to the large number of congeners and isomers for the same class of substances. For example, polychlorinated biphenyls represent a group of 209 different chemical compounds ( Persistent organic pollutants represent a family of substances that is not strictly speaking "new" as it has been known for more than 50 years to date, but this group of pollutants is still of concern. Indeed, their presence in the aquatic environment is not a recent phenomenon, but this problem has become more widely evident over the last decade thanks to the constant improvement of analytical techniques and more regular monitoring of aqueous compartments, including sediments, and organisms. Persistent organic pollutants in the Arctic atmosphere have been investigated since the 1970s when the first atmospheric measurements revealed their presence in this pristine polar environment [START_REF] Kallenborn | Atmospheric long-range transport of persistent organic pollutants (POPs) into Polar Regions. In Zeng EY (ed) Persistent organic pollutants (POPs): analytical techniques, environmental fate and biological effects[END_REF]. Nevertheless, this family of substances is regularly updated, for example, the emerging perfluoro alkyl and polyfluoro alkyl substances have been classified as persistent organic pollutants [START_REF] Puzyn | Organic pollutants ten years after the Stockholm convention[END_REF][START_REF] Vestergren | Human dietary exposure to per-and poly-fluoroalkyl substances (PFASs) (chapter 12)[END_REF][START_REF] Zeng | Persistent organic pollutants (POPs): analytical techniques, environmental fate and biological effects[END_REF]. Only limited information is available for these "newly" identified substances.

Persistent organic pollutants are transported from primary and secondary sources (industry, agriculture, urbanized areas, transport, etc.) through the atmosphere, and they can be transported over long distances to areas of the World through natural atmospheric and oceanic processes where there are no anthropogenic activities, e.g., in Arctic soils [START_REF] Gioia | Sources, transport and fate of organic pollutants in the oceanic environment (Chapter 8)[END_REF][START_REF] Cabrerizo | Legacy and emerging persistent organic pollutants (POPs) in terrestrial compartments in the high Arctic: sorption and secondary sources[END_REF]. Indeed, they are found all over the World, even in areas where these substances have never been used or produced [START_REF] Puzyn | Organic pollutants ten years after the Stockholm convention[END_REF][START_REF] Kallenborn | Atmospheric long-range transport of persistent organic pollutants (POPs) into Polar Regions. In Zeng EY (ed) Persistent organic pollutants (POPs): analytical techniques, environmental fate and biological effects[END_REF].

The majority of persistent organic pollutants identified so far are banned or restricted worldwide due to concerns about their harmfulness to human health and ecosystems. They are indeed substances of global concern due to their toxicity, persistence, bioaccumulation and long-range transport (Puzyn and Mostrag-Szlichtyng 2012; [START_REF] Datta | Fate and transport modelling of emerging pollutants from watersheds to oceans: a review[END_REF]. Once released into the environment, persistent organic pollutants, that remain intact for exceptionally long periods of time (even some long-banned substances persist in the environment), are widely distributed in all environmental compartments (water, sediment, soil and atmosphere). They accumulate in the fatty tissue of living organisms (due to their low solubility and high lipophilicity, the molecules are subject to bioaccumulation in human and animal fatty tissues, and then biomagnify along food chains), being toxic to humans and wildlife [START_REF] Mortimer | Persistent organic pollutants in foods: science, policy and regulation (chapter 1)[END_REF][START_REF] Harmon | (ed) Persistent organic pollutants (POPs): analytical techniques, environmental fate and biological effects[END_REF]. Indeed, due to their special intrinsic physical and chemical properties, they are resistant to environmental degradation through physical, chemical and biological processes [START_REF] Harmon | (ed) Persistent organic pollutants (POPs): analytical techniques, environmental fate and biological effects[END_REF][START_REF] Zeng | Persistent organic pollutants (POPs): analytical techniques, environmental fate and biological effects[END_REF]. Exposure to persistent organic pollutants can lead to serious health effects, including certain cancers, birth defects, immune and reproductive system dysfunction, increased susceptibility to disease and damage to the central and peripheral nervous systems. Some substances are also known as disrupting endocrine compounds.

In order to eliminate or reduce the release of persistent organic pollutants into the environment, several international treaties have been established, which call for efforts and actions by the international community, such as the Protocol to the UNECE Regional Convention on Long Range Transboundary Air Pollution (CLRTAP) and the Stockholm Convention on persistent organic pollutants. The Stockholm Convention (signed in 2001; Puzyn and Mostrag-Szlichtyng 2012), which has 184 countries/regions member signataries, listed 12 original persistent organic pollutants in 2004 and has updated it over the last decades. These instruments have established strict international regimes for lists of persistent organic pollutants, including 16 chemicals in the UNECE Protocol and 12 original chemicals (the "dirty dozen" including DDT, aldrin, endrin, heptachlor, polychlorinated biphenyls, polychlorinated dibenzofurans and polychlorinated dibenzo dioxins) and 16 newly added chemicals in the Stockholm Convention.

Lake ecosystems, composed of the water body, sediments, organisms, surrounding soils and the atmosphere, are one of the major sinks for persistent organic pollutants and are also an important part of surface water systems. Persistent organic pollutants in lakes can accumulate in the fatty tissue of living organisms through the food chain and pose potential risks to humans [START_REF] Puzyn | Organic pollutants ten years after the Stockholm convention[END_REF][START_REF] Duedahl-Olesen | Polycyclic aromatic hydrocarbons (PAHs) in foods (chapter 13)[END_REF][START_REF] Schrenk | Dioxins and polychlorinated biphenyls (PCBs) in foods (chapter 9)[END_REF][START_REF] Mortimer | Persistent organic pollutants in foods: science, policy and regulation (chapter 1)[END_REF]. Legacy persistent organic pollutants, such as polycyclic aromatic hydrocarbons, organochlorine pesticides, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans and polybrominated diphenyl ethers, have been commonly detected and reported in various lake ecosystems, while emerging persistent organic pollutants such as perfluorinated compounds, polychlorinated naphthalenes, tetrabromobisphenol A and hexabromocyclododecane have been relatively less detected or reported, but these chemicals are also of great concern. Figure 1.6 shows the average concentrations of various persistent organic pollutants in the Chinese Taihu lake ecosystem. Lake Taihu, located in the southern Jiangsu province and northern Zhejiang province, is the third largest freshwater lake in China and has provided local communities with valuable fisheries for centuries. There are 38 cities and more than 40 million people living around the lake, Taihu Basin being one of the most developed regions in China [START_REF] Li | Ecosystem structure and functioning of Lake Taihu (China) and the impacts of fishing[END_REF][START_REF] Wang | Pollution in Taihu Lake, China: causal chain and policy options analyses[END_REF]). Various carcinogenic persistent organic pollutants from the past are commonly detected in typical lake ecosystems in Europe and Asian. Organochlorine pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons are the main persistent organic pollutants in water bodies [START_REF] Javedankherad | Levels and distribution of organochlorine pesticides and polychlorinated biphenyls in water and sediment from the International Anzali Wetland, North of Iran[END_REF]), sediments [START_REF] De Mora | Organochlorinated compounds in Caspian Sea sediments[END_REF][START_REF] Boehm | Aspects of polycyclic aromatic hydrocarbons in offshore sediments in the Azeri sector of the Caspian Sea[END_REF][START_REF] Nemirovskaya | Origin of hydrocarbons in the particulate matter and bottom sediments of the northern shelf of the Caspian Sea[END_REF][START_REF] Varnosfaderany | Distribution and characteristic of PAHs in sediments from the Southwest Caspian Sea, Guilan Province, Iran[END_REF][START_REF] Baniemam | Seasonal variation of polycyclic aromatic hydrocarbons in the surface sediments of the southern Caspian Sea[END_REF], organisms [START_REF] Rajaei | Persistent organic pollutants in muscle and feather of ten Avian species from Mazandaran Province of Iran, on the Coast of the Caspian Sea[END_REF][START_REF] Mashroofeh | Distribution and composition pattern of polycyclic aromatic hydrocarbons in different tissues of sturgeons collected from Iranian coastline of the Caspian Sea[END_REF], and the surrounding soils and atmosphere [START_REF] Aliyeva | Organochlorine pesticides and polychlorinated biphenyls in air and soil across Azerbaijan[END_REF][START_REF] Aliyeva | The legacy of persistent organic pollutants in Azerbaijan: an assessment of past use and current contamination[END_REF][START_REF] Shahbazi | Elevated concentrations of pesticides and PCBs in soils at the Southern Caspian Sea (Iran) are related to land use[END_REF] of the Caspian Sea located between Europe and Asia, the World's largest lake.

The levels of these persistent organic pollutants in the Caspian Sea ecosystems are at a scale of approximately ng/g, with polycyclic aromatic hydrocarbons having a relatively higher concentration. However, persistent organic pollutants newly added to the Stockholm Convention, such as polychlorinated naphthalenes, perfluorinated compounds, hexabromocyclododecane, etc., are rarely studied in the Caspian Sea at present. Persistent organic pollutants, including organochlorine pesticides, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers, polychlorinated naphthalenes, hexabromocyclododecane, perfluorinated compounds and tetrabromobisphenol A, are also present in different environmental compartments and biota in Chinese lake ecosystems [START_REF] Qiu | Organochlorine pesticides in the air around the Taihu Lake, China[END_REF][START_REF] Zhang | Polychlorinated dibenzo-p-dioxins/furans and polychlorinated biphenyls in sediments and aquatic organisms from the Taihu Lake, China[END_REF][START_REF] Qiao | Composition, sources, and potential toxicological significance of PAHs in the surface sediments of the Meiliang Bay, Taihu Lake, China[END_REF][START_REF] Wang | Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China[END_REF][START_REF] Wen | Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in surface sediment and bivalve from the Changjiang Estuary, China[END_REF][START_REF] Yang | Occurrence and partition of perfluorinated compounds in water and sediment from Liao River and Taihu Lake, China[END_REF][START_REF] Yu | Polybrominated diphenyl ethers and polychlorinated biphenyls in freshwater fish from Taihu Lake, China: their levels and the factors that influence biomagnification[END_REF][START_REF] Zhang | Intakes of omega-3 polyunsaturated fatty acids, polybrominated diphenyl ethers and polychlorinated biphenyls via consumption of fish from Taihu Lake, China: a risk-benefit assessment[END_REF]Zhou et al. 2012a, b;[START_REF] Xu | Levels and distribution of tetrabromobisphenol A and hexabromocyclododecane in Taihu Lake, China[END_REF][START_REF] Xu | AhR-mediated activities and compounds in sediments of Meiliang Bay, Taihu Lake, China determined by in vitro bioassay and instrumental analysis[END_REF]Wang et al. 2016a, b;[START_REF] Cui | Fast analysis of 4-tertoctylphenol, pentachlorophenol and 4-nonylphenol in river sediments by QuEChERS extraction procedure combined with GC-QqQ-MS/MS[END_REF][START_REF] Liu | Research progress on the distribution and enrichment of persistent organic pollutants in lake organisms in China[END_REF][START_REF] Wei | Organohalogenated Contaminants (OHCs) in surface sediments and water of East Dongting Lake and Hong Lake, China[END_REF][START_REF] Xiang | Contamination characteristics and ecological risk assessment of polybrominated diphenyl ethers in the North Pacific Ocean[END_REF].

Recently, the presence of perfluorinated compounds in the environment has been of great concern. Levels of perfluorinated compounds in the water body of Chinese lakes have averaged between 30 and 50 ng/L and perfluorooctanoic acid and perfluorooctane sulfonate were the most frequent perfluorinated compounds [START_REF] Yang | Occurrence and partition of perfluorinated compounds in water and sediment from Liao River and Taihu Lake, China[END_REF][START_REF] Gao | Persistent organic chemicals in the environment: status and trends in the Pacific Basin Countries[END_REF]. Mean concentrations of organochlorine pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated diphenyl ethers, polychlorinated dibenzo-p-dioxins and dibenzofurans, perfluorinated compounds and hexabromocyclododecane in samples of biota from various Chinese lakes are usually at ng/g levels [START_REF] Liu | Research progress on the distribution and enrichment of persistent organic pollutants in lake organisms in China[END_REF]. In summary, European and Asian lake ecosystems are contaminated to varying degrees by various persistent organic pollutants. There are large differences in the levels of persistent organic pollutants between different lake ecosystems and other environmental media. Further studies on newly added persistent organic pollutants are needed in the future to better understand their environmental fate and ultimate control.

Persistent organic pollutants, old and new, are also widely distributed in the water bodies, sediments, organisms, surrounding soils and atmosphere of lake ecosystems typical of North America and Africa. Lake Superior is the largest freshwater lake in the World and also the largest of the Great Lakes in North America. Polychlorinated biphenyls and organochlorine pesticides occuring in the Lake Superior water body in the 1990s were at ng/g range and by 2018 they were at pg/g levels, which is lower than in lakes in Europe and Asia [START_REF] Jeremiason | PCBs in lake-superior, 1978-1992decreases in water concentrations reflect loss by volatilization[END_REF][START_REF] Ruge | Concentrations, trends, and air-water exchange of PCBs and organochlorine pesticides derived from passive samplers in Lake Superior in 2011[END_REF]. Polychlorinated dibenzo-p-dioxins and dibenzofurans, polybrominated diphenyl ethers and polychlorinated biphenyls were found in Lake Superior sediments at ng/g magnitude, which was comparable to that of European and Asian lakes [START_REF] Pearson | Atmospheric inputs of polychlorinated dibenzo-p-dioxins and dibenzofurans to the Great Lakes: compositional comparison of PCDD and PCDF in sediments[END_REF][START_REF] Shen | Occurrence and sources of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in surficial sediments of Lakes Superior and Huron[END_REF].

In addition to organochlorine pesticides and polychlorinated biphenyls, some emerging persistent organic pollutants such as polybrominated diphenyl ethers, hexabromocyclododecane, polychlorinated naphthalenes and perfluorinated compounds were also present in Lake Superior organisms [START_REF] Kannan | Polychlorinated naphthalenes and polychlorinated biphenyls in fishes from Michigan waters including the Great Lakes[END_REF][START_REF] Luross | Spatial distribution of polybrominated diphenyl ethers and polybrominated biphenyls in lake trout from the Laurentian Great Lakes[END_REF][START_REF] Dykstra | Contaminant concentrations and reproductive rate of Lake Superior bald eagles, 1989-2001[END_REF][START_REF] Fernie | Historical contaminants, flame retardants, and halogenated phenolic compounds in Peregrine Falcon (Falco peregrinus) Nestlings in the Canadian Great Lakes Basin[END_REF][START_REF] Furdui | Effect of solution pH on the removal of paracetamol by activated carbon of Dende coconut mesocarp[END_REF]. Polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers, organochlorine pesticides, polychlorinated naphthalenes and polychlorinated biphenyls were present in the surrounding atmosphere [START_REF] Hillery | Temporal and spatial trends in a long-term study of gas phase PCB concentrations near the Great Lakes[END_REF][START_REF] Strandberg | Concentrations and spatial variations of polybrominated diphenyl ethers and other organohalogen compounds in Great Lakes air[END_REF][START_REF] Fernandez | Atmospheric gas-particle partitioning of polycyclic aromatic hydrocarbons in high mountain regions of Europe[END_REF][START_REF] Helm | Spatial distribution of polychlorinated naphthalenes in air over the great lakes and air-water gas exchange in Lake Ontario[END_REF]. Lake Tanganyika is a freshwater lake located in Central Africa. Reports of persistent organic pollutants in Lake Tanganyika are mainly related to lake organisms. Organochlorine pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers and hexabromocyclododecane were detected in fish samples from Lake Tanganyika [START_REF] Mahugija | Determination of dichlorodiphenyltrichloroethane (DDT) and metabolites residues in fish species from Eastern Lake Tanganyika[END_REF][START_REF] Polder | Levels and patterns of persistent organic pollutants (POPs) in tilapia (Oreochromis sp.) from four different lakes in Tanzania: geographical differences and implications for human health[END_REF]. Among these reported persistent organic pollutants, the concentration of polychlorinated biphenyls in fish samples ranged from 36 to 167 ng/g, which is generally lower than in Asian lakes. In addition, the contamination of persistent organic pollutants in Lake Tanganyika was lower or comparable to that in other parts of Africa [START_REF] Manirakiza | Persistent chlorinated pesticides and polychlorinated biphenyls in selected fish species from Lake Tanganyika, Burundi, Africa[END_REF].

Polybrominated diphenyl ethers have raised new concerns in recent decades. Some studies have focused on polybrominated diphenyl ether contamination in the North Pacific Ocean, where the World's largest fishery, that of Hokkaido, is being lacerated. It is the main source of seafood for people living in countries along the North Pacific coast, especially those living in Japan, South Korea and China. However, this coast is also the World's largest producer and consumer of polybrominated diphenyl ethers. The use and emissions of polybrominated diphenyl ethers in this region are significant, and pollution by polybrominated diphenyl ethers is becoming an increasingly serious problem. [START_REF] Xiang | Contamination characteristics and ecological risk assessment of polybrominated diphenyl ethers in the North Pacific Ocean[END_REF] showed that the current concentration of polybrominated diphenyl ethers in the atmosphere, water, sediments and organisms in the North Pacific Ocean is 0.14 to 896 pg/m 3 , 3 to 4360 pg/L, 0.24 to 7397.7 ng/g dry weight and 0.56 to 3930 ng/g lipid weight, respectively. The predicted concentration of polybrominated diphenyl ethers in the Hokkaido fishery could be 4.6 to 9 pg/m 3 (air), 106 to 341 pg/L (water), 3.4 to 248 ng/g dry weight (sediment) and 5 to 64.7 ng/g lipid weight (biota). The concentration of polybrominated diphenyl ethers in the atmosphere, water bodies, sediments and organisms in the North Pacific has a characteristic near-shore > ocean or low latitude > high latitude distribution [START_REF] Xiang | Contamination characteristics and ecological risk assessment of polybrominated diphenyl ethers in the North Pacific Ocean[END_REF].

From a global perspective, lake ecosystems are contaminated to varying degrees by several persistent organic pollutants, both from past and recent contamination. Although many studies have been conducted on these substances in lake ecosystems, these studies have mainly focused on traditional persistent organic pollutants such as organochlorine pesticides, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans, while emerging persistent organic pollutants such as polychlorinated naphthalenes, perfluorinated compounds, hexabromocyclododecane, etc. are relatively less reported. The extent and significance of all these substances are still largely unknown. Environmental risk assessing of persistent organic pollutants remains particularly difficult, not only in lake ecosystems, but also in freshwater and marine ecosystems.

These ecosystems are fragile, living at the rate of anthropogenic disturbances (pollution, artificialization, withdrawals), increasingly vulnerable for example to climate change, but essential to life in general. Indeed, lake ecosystems are important freshwater resources closely linked to human life, but our understanding of pollution by persistent organic pollutants in lake ecosystems is not yet sufficient. A better understanding of these substances, in terms of their degradation, behavior, accumulation, transfer, toxicity and impact, still requires research in the different environmental compartments and living organisms of these systems. More comprehensive international health policies and standards are also needed in the future.

Monitoring of Emerging Contaminants in Portuguese Rivers

Portugal is on the top three of countries with more studies in the field of surface water even by normalizing the amount of reports by the number of inhabitants per country, according to a recent review on the environmental monitoring of water organic pollutants dedicated to the literature published between 2012 and 2018 [START_REF] Sousa | A review on environmental monitoring of water organic pollutants identified by EU guidelines[END_REF]. That review paper provides an overview of the worldwide occurrence of contaminants identified by European Union guidelines, namely priority substances of European Directive 39/2013/EU and contaminants of emerging concern of Watch Lists of European Decisions 495/2015/EU and 840/2018/EU, and presenting also comprehensive data about other specific organic pollutants not considered in those European Union documents and with reported high concentrations and frequencies. Another review paper covering the period between 2001 and 2015 systematically overviewed the published data on the monitoring of industrial compounds, natural and synthetic estrogens, phytoestrogens and phytosterols, pharmaceuticals, and pesticides in the Portuguese aquatic environment (Ribeiro et al. 2016b). The data collected in that review show that some compounds were determined at high concentrations in the studies performed between 2001 and 2015, namely industrial and household compounds (e.g., bisphenol A, alkylphenols and alkylphenol polyethoxylates) found from few ng/L to dozens of μg/L, in agreement with other European countries such as Spain, Switzerland, Netherlands, and France (Ribeiro et al. 2016b). In the case of natural and pharmaceutical estrogens, they were detected always at ng/L levels in Portuguese surface waters in the reviewed literature, similar or higher than those concentrations reported in European countries (Ribeiro et al. 2016b). While phytoestrogens are described as frequently studied and detected at μg/L range, the authors pointed out that most publications about pharmaceuticals in Portuguese surface waters published before 2016 referred only few therapeutic classes in the north of Portugal and the majority of them consisted in the application of new analytical methods rather than consistent monitoring data (Ribeiro et al. 2016b). A wide range of classes of pesticides including priority substances of European Directive 39/2013/EU were compiled in that review from 2001 to 2015, some of them up to μg/L, including atrazine that was already banned in Europe (Ribeiro et al. 2016b). The present section aims to update the information about the occurrence and distribution of emerging contaminants in Portuguese rivers (Fig. 1.7) and results from a literature survey comprising reports published since 2015 in Scopus database, using as keywords: "river water", "surface water" or "estuarine water" and "Portugal" or "Portuguese", and "monitor" or "occurrence".

In the last years, natural organic compounds have been studied in Portuguese rivers, namely phytoestrogens and phytosterols that are found in many plants and mycotoxins produced by fungi. One study monitoring these classes in the Douro River estuary reported the maximum concentration of daidzein (up to 277.4 ng/L) in the summer (Ribeiro et al. 2016a), whereas the highest value in another seasonal study performed by the same research group in the Ave River was determined in the spring (up to 404.0 ng/L) (Ribeiro et al. 2016c). In that river, a seasonal trend for phytoestrogens and phytosterols was verified and the largest level of coumestrol (up to 165.0 ng/L) was observed in the summer. Interestingly, this compound was not detected in any sample collected in the Douro monitoring campaign (Ribeiro et al. 2016a). Both reports showed that the mycotoxin deoxynivalenol was ubiquitously found up to 373.5 ng/L in the Douro (Ribeiro et al. 2016a) and between 59.5 to 642.4 ng/L in the Ave (Ribeiro et al. 2016c), whereas the micotoxin zearalenone and its metabolite α-zearalenol were only detected in spring and summer in the Douro (Ribeiro et al. 2016a). This last finding is in agreement with another monitoring study in seven Portuguese rivers and one creek, where the highest concentration of zearalenone was reported during spring. In that survey, it was estimated a contamination frequency of 23.7% for this mycotoxin, with concentrations ranging between 5.6 and 82.6 ng/L [START_REF] Laranjeiro | The mycoestrogen zearalenone in Portuguese flowing waters and its potential environmental impact[END_REF]. In general, the highest values found in the last years are quite lower than those reviewed in the previous period 2001-2015 by Ribeiro et al. (2016b). Industrial and household compounds have been also monitored in Portuguese rivers. In a monitoring program developed in Mira River over a 1-year period, including also natural and pharmaceutical estrogens, phytoestrogens and the phytosterol sitosterol, both estrogens and industrial/household pollutants were found at high concentrations in all sampling locations, including some positioned in environmental protected areas [START_REF] Rocha | Pollution by oestrogenic endocrine disruptors and β-sitosterol in a south-western European river (Mira, Portugal)[END_REF]. Specifically, the annual average of industrial/household pollutants was of ca. 1.3μg/L, whereas values at ng/L levels were described for phytoestrogens and sitosterol [START_REF] Rocha | Pollution by oestrogenic endocrine disruptors and β-sitosterol in a south-western European river (Mira, Portugal)[END_REF]. Another recent study targeting endocrine disruptor compounds in Minho, Ave and Mondego River estuaries, reported quite high concentrations of alkylphenols and alkylphenol ethoxylates (up to 4855 ng/L) despite those of the natural estrogens were markedly lower than previous surveys [START_REF] Rocha | Pollution by oestrogenic endocrine disruptors and β-sitosterol in a south-western European river (Mira, Portugal)[END_REF].

Regarding personal care products, one study performed in northern Portuguese rivers in the summer (2018) targeted 43 compounds and detected 28 substances [START_REF] Celeiro | Determination of multiclass personal care products in continental waters by solid-phase microextraction followed by gas chromatography-tandem mass spectrometry[END_REF]): fragrances up to 200 ng/L (citronellol), limonene, α-isomethylionone, tonalide and galaxolide in all samples, the latter up to 379 ng/L; phthalates up to 92 ng/L (benzylbutylphthalate), including the priority substance diethylhexylphthalate determined at 88 ng/L in one sampling point; the priority substance antioxidant butylhydroxytoluene between 8 and 25 ng/L in half of the samples; and UV filters up to 254 ng/L (benzophenone 3).

In the last years, pharmaceuticals have been extensively monitored by some research groups. A wide group of 66 human and veterinary pharmaceuticals belonging to seven therapeutic groups was monitored in Tejo estuarine waters and the therapeutic families with an overall frequency of detection higher than 90% were antibiotics, β-blockers, antihypertensives, lipid regulator and anti-inflammatories (Reis- [START_REF] Santos | Development of an analytical methodology for the analysis of priority cytostatics in water[END_REF]). The highest concentrations of each class were 304 ng/L for antidepressants (sertraline), 51.8 ng/L for non-steroidal anti-inflammatories (diclofenac), 77.0 ng/L for lipid regulators (gemfibrozil), 161.9 ng/L for antihypertensives (ibersartan) and 128.0 ng/L for antibiotics (doxycycline) (Reis- [START_REF] Santos | Development of an analytical methodology for the analysis of priority cytostatics in water[END_REF]. Another one-year occurrence study published before targeting 23 pharmaceuticals in Tejo and Mondego Rivers (Pereira et al. 2017a), showed one site in Tejo River with comparable concentrations of diclofenac, gemfibrozil and bezafibrate. In that study, pharmaceuticals were found in 27.8% of the samples at ng/L levels, with the following therapeutic families having the highest detection frequencies and mean concentrations: selective serotonin reuptake inhibitors, anti-inflammatories and antibiotics (Pereira et al. 2017a). The authors confirmed the impact of wastewater treatment plants by an increase of the mean concentrations downstream and the impact of lower river flow rates on increasing detection frequencies and concentrations (Pereira et al. 2017a). In this sense, despite the risk quotients were higher than one only for two pharmaceuticals, the authors stressed the ecotoxicological pressure especially due to water scarcity in drought periods, which may raise the risk in rivers located in the Iberia region (Pereira et al. 2017a). A study carried out in the Lisbon's drinking water supply system included the analysis of 31 pharmaceuticals in surface waters from Tejo and Zêzere Rivers, where 15 and 10 pharmaceuticals were detected at ng/L levels, respectively (de Jesus [START_REF] De | Occurrence of pharmaceuticals in a water supply system and related human health risk assessment[END_REF]. Caffeine, erythromycin, acetaminophen, sulfadiazine, sulfapyridine, sulfamethoxazole, carbamazepine and atenolol were quantified in both rivers; propranolol, sulfamethazine, gemfibrozil, indomethacin, ibuprofen, diclofenac, and naproxen were present in the Tejo River; and nimesulide was only quantified in the Zêzere River (de Jesus [START_REF] De | Occurrence of pharmaceuticals in a water supply system and related human health risk assessment[END_REF]. In that study, the risk assessment was performed for human health and it was suggested that the exposure to residual pharmaceuticals in drinking water would be particularly improbable. One environmental relevant therapeutic class is the cytostatics as the cancer incidence has raised worldwide and thus their consumption has evidently increased over the last years. From the seven cytostatics (cyclophosphamide, capecitabine, mycophenolic acid, imatinib, bicalutamide, prednisone and 5-fluorouracil) determined in river water samples in a very recent study encompassing also wastewaters, only mycophenolic acid was detected in Uíma, Douro and Leça Rivers, at average concentrations of 210, 211 and 541 ng/L, respectively [START_REF] Santos | Development of an analytical methodology for the analysis of priority cytostatics in water[END_REF]. Twenty-seven pharmaceuticals including antibiotics and psychiatric drugs were also analysed in Douro and Leça Rivers [START_REF] Fernandes | Antibiotics and antidepressants occurrence in surface waters and sediments collected in the north of Portugal[END_REF]). In that study, higher frequency and concentrations of pharmaceuticals were found in the Leça River, where six antibiotics (azithromycin, ciprofloxacin, clarithromycin, moxifloxacin, ofloxacin, and trimethoprim) were found, the highest concentration was registered for azithromycin (2819 ng/L), and fluoxetine was the most detected pharmaceutical [START_REF] Fernandes | Antibiotics and antidepressants occurrence in surface waters and sediments collected in the north of Portugal[END_REF]. Interestingly, in the same report, none of the studied antibiotics was detected in river samples of Douro River [START_REF] Fernandes | Antibiotics and antidepressants occurrence in surface waters and sediments collected in the north of Portugal[END_REF].

Some occurrence studies have been developed in the last years, by simultaneously targeting pharmaceuticals and other classes of compounds, namely pesticides. One recent monitoring program performed recently in four rivers (Ave, Antuã, Cértima, and Leça) described the spatial and temporal variations of 39 priority substances and contaminants of emerging concern, some belonging to European Directive 39/2013/EU, European Decisions 840/2018/EU and 495/2015/EU [START_REF] Barbosa | Spatial and seasonal occurrence of micropollutants in four Portuguese rivers and a case study for fluorescence excitation-emission matrices[END_REF]. From the 13 pollutants detected in all the rivers, various pharmaceuticals were detected (up to 396 ng/L) and the priority pesticide isoproturon was found up to 92 ng/L [START_REF] Barbosa | Spatial and seasonal occurrence of micropollutants in four Portuguese rivers and a case study for fluorescence excitation-emission matrices[END_REF]. The industrial priority substance perfluorooctanesulfonic acid was detected below its quantification limit in the Antuã, Cértima, and Leça [START_REF] Barbosa | Spatial and seasonal occurrence of micropollutants in four Portuguese rivers and a case study for fluorescence excitation-emission matrices[END_REF]. Atrazine, a priority substance of European Union Directive 39/2013 already banned, was also detected in Ave, Antuã and Leça (up to 41 ng/L), whereas simazine was found in the Cértima and Leça [START_REF] Barbosa | Spatial and seasonal occurrence of micropollutants in four Portuguese rivers and a case study for fluorescence excitation-emission matrices[END_REF], both pesticides being found at higher concentrations than those reported in the Arade River by [START_REF] Gonzalez-Rey | Occurrence of pharmaceutical compounds and pesticides in aquatic systems[END_REF]. The neonicotinoids acetamiprid and imidacloprid of the European Decision 840/2018/EU were only detected during the dry season in the Ave [START_REF] Barbosa | Spatial and seasonal occurrence of micropollutants in four Portuguese rivers and a case study for fluorescence excitation-emission matrices[END_REF]).

In the same report, higher concentrations were observed downstream of industrial areas and urban wastewater treatment plants [START_REF] Barbosa | Spatial and seasonal occurrence of micropollutants in four Portuguese rivers and a case study for fluorescence excitation-emission matrices[END_REF]. In another study published by the same group, all the contaminants of emerging concern preconized in the Watch List in force at the time of that monitoring program (European Decision 495/2015/EU) were monitored during four seasons in two Portuguese rivers located in the northern region, Ave and Sousa [START_REF] Sousa | Monitoring of the 17 EU Watch List contaminants of emerging concern in the Ave and the Sousa Rivers[END_REF]. In that study, 13 contaminants of emerging concern were found, being diclofenac, 2-ethylhexyl 4-methoxycinnamate, and azithromycin the most frequent compounds and diclofenac, 2-ethylhexyl 4-methoxycinnamate and imidacloprid those determined at the highest concentrations [START_REF] Sousa | Monitoring of the 17 EU Watch List contaminants of emerging concern in the Ave and the Sousa Rivers[END_REF]. The same authors reported the first spatial distribution of 37 pollutants in the entire Portuguese coast, including the ocean shore and the nearest river discharging on it [START_REF] Sousa | Monitoring of the 17 EU Watch List contaminants of emerging concern in the Ave and the Sousa Rivers[END_REF]. This monitoring program included some priority substances and contaminants of emerging concern of the European Watch List (European Decisions 495/2015/EU and 840/2018/EU; EU 2015, 2018). In general, the authors found high concentrations of diclofenac, tramadol and carbamazepine, the latter being ascribed as having medium to high risk for algae (Sousa et al. 2020). While some pharmaceuticals and perfluorooctanesulfonic acid were largely distributed, atrazine and alachlor were also determined in most samples, with the concentrations of alachlor in some locations being considered as medium to high risky (Sousa et al. 2020). Interestingly, higher levels were described in some seawater samples in comparison to that of the nearest estuarine site, which was attributed to the possible direct discharge into the sea (Sousa et al. 2020). The first study on the presence of pharmaceutical compounds and pesticides in the Arade River estuary included 19 pharmaceuticals and 47 pesticides, some of which defined as priority substances of European Directive 39/2013/EU or included in the European Decision 495/2015/EU (EU 2013; [START_REF] Gonzalez-Rey | Occurrence of pharmaceutical compounds and pesticides in aquatic systems[END_REF]. In that study, the detected compounds varied temporally and seasonally, except the stimulant caffeine (804 ng/L), which occurred without any remarkable differences. Other study targeting caffeine as anthropogenic indicator in the Lis River over an 11-month period, reported its presence in all river samples ranging from 25.3 to 321 ng/L, with its highest levels found downstream of effluent discharge points, confirming that it could be an effective indicator of human-born pollution [START_REF] Paíga | Monitoring survey of caffeine in surface waters (Lis River) and wastewaters located at Leiria Town in Portugal[END_REF]. Besides caffeine, those compounds found at highest concentrations in the Arade River were the antiasthmatic theophylline (184 ng/L), the analgesic paracetamol (88 ng/L) and the fungicide carbendazim (45 ± 18 ng/L) [START_REF] Gonzalez-Rey | Occurrence of pharmaceutical compounds and pesticides in aquatic systems[END_REF]. In turn, atrazine, diuron, isoproturon and simazine were found at few ng/L and below the environmental quality standards.

Some monitoring surveys focusing on pesticides have been also published. Surface waters of the Lezíria do Tejo agricultural area were monitored and the measured environmental concentrations for the 19 pesticides were compared with their environmental quality standards for risk assessment, being the risk demonstrated in 100% of the samples containing insecticides, which represented 60% of the total risk identified (Pereira et al. 2017b). One occurrence study was performed between 2002 and 2004 in the river basins Mondego, Sado and Tejo in order to assess the risk of 29 pesticides and metabolites, including priority substances and other compounds used in dominant crops of a number of agricultural areas within the catchment of these Mediterranean river basins (Silva et al. 2015a, b). In that study, 20 substances were detected, from which seven are priority substances (alachlor, atrazine, chlorfenvinphos, chlorpyrifos, endosulfan, simazine and terbutryn) and remarkably all exceeded their individual environmental quality standards values. Other specific pollutants namely molinate, oxadiazon, pendimethalin, propanil, terbuthylazine, and the metabolite desethylatrazine, had non-acceptable aquatic risks (Silva et al. 2015a). The authors highlighted the need to monitor such substances not only at European Union, but also at local/river-basin/national level, allowing to describe the exceedances of the environmental quality standards (Silva et al. 2015a). The most frequently found compounds in a previous study reporting 29 pesticide compounds (21 herbicides, 5 insecticides and 3 metabolites) in surface waters of Mondego, Sado and Tejo from 2002 and 2008 were: chlorfenvinphos (mean 0.16μg/L), propanil (mean 0.007μg/L) and the metabolite 3,4-dichloroaniline (mean 0.33μg/L) in all rivers; molinate (mean 1.03μg/L) and oxadiazon (mean 0.006μg/L) in Mondego and Sado Rivers; and atrazine (mean 0.16μg/L), simazine (mean 0.08μg/L) and metolachlor (mean 0.06μg/L) in Mondego and Tejo Rivers (Silva et al. 2015a). Endosulfan was also detected in all rivers, but less frequently (3-7%) and with a quite lower mean value of 0.0008μg/L (Silva et al. 2015a). In that study, the authors predicted the aquatic risk of the measured pesticide mixtures for primary producers, arthropods and fish in the three Portuguese river basins and proposed a ranking per taxonomic group and river basin for the relative contribution of individual compounds or groups sharing the same mode of action, where the highest toxicity role was observed for oxadiazon on primary producers and for the organophosphorus insecticides chlorfenvinphos and chlorpyrifos on arthropods and fish, respectively. It is noteworthy that a study conducted between 2010 and 2011 in the Mondego estuary, comprising 56 priority pesticides (insecticides, herbicides and fungicides), reported more than half of the quantified pesticides above the maximum values set by the European Directives (98/83/EC and 2013/39/EU), a potential risk for the pesticide mixture at the maximum concentrations found, and a significant toxic effect for Artemia salina, with observed affected locomotion [START_REF] Cruzeiro | Environmental assessment of pesticides in the Mondego River Estuary (Portugal)[END_REF].

In another spatial and temporal monitoring study encompassing the pesticides atrazine, azoxystrobin, bentazon, λ-cyhalothrin, penoxsulam and terbuthylazine in the Mondego estuary, azoxystrobin was found as the most frequently detected pesticide (Rodrigues et al. 2018a), which had been also reported in all aqueous samples collected seasonally during 2012-2013 in a wetland of worldwide interest (Ria Formosa Lagoon) (Cruzeiro et al. 2015a), where pesticide concentrations surpassed those recommended by European Directive 2013/39/EU in two monitoring studies (Cruzeiro et al. 2015a, b). In the Mondego (Rodrigues et al. 2018a), atrazine was the second most detected, reinforcing that this priority substance should be monitored despite its ban. Although the concentrations of pesticides in estuarine water were estimated to lead to low risk to estuarine organisms, all pesticides were bioaccumulated by bivalves and triazine pesticides were found also in macroalgae (Rodrigues et al. 2018a). In the same study, the pesticides were quantified typically during summer concurring with the pesticide usage period and no severe contamination occurred during a flood event that was expected to promote the runoff of pesticides from the adjacent agricultural areas (Rodrigues et al. 2018a). The quantified residues of pesticides were also more frequent during the summer and thus in the pesticide application period in another spatial and temporal monitoring program performed in 2017 in the Sado estuary (Rodrigues et al. 2019a). That report suggested a long-term aquatic exposure for five herbicides, namely alachlor, bentazon, metobromuron, metribuzin and triclopyr, which were determined in the water samples before and after the production season (Rodrigues et al. 2019a). Regarding the potential adverse effects of the application of agricultural pesticides on the aquatic organisms in this estuary, it was not found any severe effect, even considering the potential mixture effect of pesticides (Rodrigues et al. 2019a).

The problematic of microplastics in river waters has received little attention in comparison to marine system. Two recent studies performed in Antuã River (Rodrigues et al. 2018b) and Douro river estuary (Rodrigues et al. 2019b) targeted this environmental issue. The first study on the occurrence of microplastics in freshwater systems performed in Portugal was developed in the Antuã River during March and October 2016, showing a correlation of their occurrence with the urbanization and industrial activities, with an abundance in water up to 193 items/m 3 in March and up to 1265 items/m 3 in October (Rodrigues et al. 2018b). It was verified a higher abundance in October than in March for almost all sampling sites (one exception) and a decrease from upstream to downstream areas (Rodrigues et al. 2018b). Generally, the most frequently found plastic type was foam (>50%) and the least was pellets, but fibers were the dominant type during March (Rodrigues et al. 2018b). In the Douro report performed between from 2016 and 2017, the authors found a total of 2152 particles, with an average density of 17.06 items/100 m 3 , including fibers, soft and hard plastic, colourful and transparent plastic, being hard fragments and fibers the most frequent (Rodrigues et al. 2019b). In the same study, an average ratio of fish larvae to microplastics was found to be greater than one in some months, highlighting the possible ingestion by fish and the resulting impact in these communities (Rodrigues et al. 2019b).

All these results show that we still need to mobilise to protect water resources in order to guarantee the sustainability of the ecosystems that are essential to Portugal's economy. Indeed, the spatial distribution of pollutants along the entire Portuguese mainland coast shows the need for mitigation measures to enhance the elimination of pharmaceuticals in wastewater treatment plants and measures to control the use and discharge of pesticides and industrial compounds.

Presence of Emerging Contaminants in the Aquatic Environment in Latin America

With about one-third of the World's water resources and 24,400 m 3 of water per capita per year, Latin America is a region with abundant freshwater resource availability. This resource is nevertheless fragile, particularly impacted by increasing economic development [START_REF] Peña-Guzmán | Emerging pollutants in the urban cycle in Latin America: a review of the current literature[END_REF]. Indeed, in many Latin America countries, there is a high population density in areas suffering from poor sanitary conditions, which contributes to the contamination/pollution of rivers and reservoirs that supply water [START_REF] Caldas | Occurrence of pesticides and PPCPs in surface and drinking water in Southern Brazil: data on 4-year monitoring[END_REF][START_REF] Peña-Guzmán | Emerging pollutants in the urban cycle in Latin America: a review of the current literature[END_REF][START_REF] Starling | Occurrence, control and fate of contaminants of emerging concern in environmental compartments in Brazil[END_REF]. The chemical and physicochemical properties (e.g., water solubility, high adsorption capacity and low biodegradability) of many substances in daily use facilitate their flow without resistance reaching water sources, which can trigger problems not only for the environment but also for the health of living organisms [START_REF] Janssens | Micropollutants: a bottleneck in sustainable wastewater treatment[END_REF][START_REF] Knepper | Detection of polar organic substances relevant for drinking water[END_REF][START_REF] Kuster | Analysis and occurrence of pharmaceuticals, estrogens, progestogens and polar pesticides in sewage treatment plant effluents, river water and drinking water in the Llobregat river basin (Barcelona, Spain)[END_REF]Hernández et al. 2011a, b;[START_REF] Peña-Guzmán | Emerging pollutants in the urban cycle in Latin America: a review of the current literature[END_REF].

In a recent comprehensive review by [START_REF] Peña-Guzmán | Emerging pollutants in the urban cycle in Latin America: a review of the current literature[END_REF], it was addressed the water quality involving various aqueous compartments of Latin American countries (Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Ecuador, Guatemala, Mexico, Uruguay, and Venezuela), such as water reservoirs for human consumption, drinking water treatment plants, groundwater, surface waters, rivers and wastewater treatment plants. The authors of this survey concluded that the most frequently detected emerging substances are pharmaceuticals (mainly antibiotics), followed by personal care products, and that the most common molecules are 17-β-estradiol, bisphenol A, estrone and caffeine. Most of these chemical substances are not yet regulated by any environmental law. Peña-Guzmán et al. ( 2019) indicated that a total of 51 emerging pollutants were found in studies related to wastewater, with Ecuador being the country with the largest number of samples, followed by Mexico, Brazil and Colombia. In wastewater, caffeine had the highest concentrations (5597μg/L), followed by the cocaine metabolite benzoylecgonine (1065μg/L) and carbazepine (830μg/L). In the drinking water supply, the substance with the highest concentration (625μg/L) was ibuprofen (Brazil, Colombia, and Venezuela). For surface water sources, the contaminants with the highest concentrations were cholesterol (301μg/L), caffeine (106μg/L), stigmasterol (85.5μg/L) and bisphenol A (64.2μg/L) (Brazil, Costa Rica, Colombia, Bolivia, Chile, Mexico and Argentina). Mexico is the only country that has recorded cases of emerging contaminants in groundwater in the urban water cycle, with the highest concentrations for naproxen (2μg/L), sulfasalazine (0.78μg/L), ibuprofen (0.51μg/L), and salicylic acid (0.464μg/L). For drinking water treatment plant effluents (Brazil only), the substances identified were caffeine (4.083μg/L), nonylphenol (0.228μg/L), 17-α-ethinylestradiol (0.798μg/L), bisphenol A (0.0005μg/L), estriol (0.0003μg/L), and estrone (0.00003μg/L).

Other recent studies have also shown that pharmaceuticals, personal care products, industrial substances and pesticides are widely detected at concentrations of the same order of magnitude [START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF][START_REF] Hernández-Padilla | Assessing wastewater treatment in Latin America and the Caribbean: enhancing life cycle assessment interpretation by regionalization and impact assessment sensibility[END_REF][START_REF] Botero-Coy | An investigation into the occurrence and removal of pharmaceuticals in wastewater Colombian[END_REF][START_REF] Gilabert-Alarcón | Regulatory challenges for the use of reclaimed water in Mexico: a case study in Baja California[END_REF][START_REF] Sodré | Seasonal and spatial distribution of caffeine, atrazine, atenolol and DEET in surface and drinking waters from the Brazilian Federal District[END_REF][START_REF] Montagner | Ten years-snapshot of the occurrence of emerging contaminants in drinking, surface and ground waters and wastewaters from São Paulo State, Brazil[END_REF][START_REF] Starling | Occurrence, control and fate of contaminants of emerging concern in environmental compartments in Brazil[END_REF]. All studies concluded that these types of chemicals are persistent in the environmental compartments of Latin America; at the same time, their continuous introduction into rivers yields a complex mixture with potential synergistic effects that can result in a serious ecological risk.

As in many other countries around the World, emerging substances enter the aquatic environment of Latin America by many pathways, with the main one being the conventional wastewater treatment plants not designed to remove these type pollutants, and their discharge containing organic substances and some metabolites [START_REF] Dougherty | Occurrence of herbicides and pharmaceutical care personnel and products in surface water and groundwater around Liberty Bay, Puget Sound, Washington[END_REF][START_REF] Hernández-Padilla | Assessing wastewater treatment in Latin America and the Caribbean: enhancing life cycle assessment interpretation by regionalization and impact assessment sensibility[END_REF][START_REF] Starling | Occurrence, control and fate of contaminants of emerging concern in environmental compartments in Brazil[END_REF]. Besides, it is estimated that only 20% of municipal wastewater is treated, and in some Latin America countries, many water treatment plants are abandoned due to the high operating costs or low performance [START_REF] Hernández-Padilla | Assessing wastewater treatment in Latin America and the Caribbean: enhancing life cycle assessment interpretation by regionalization and impact assessment sensibility[END_REF]. In Mexico, less than 50% of wastewater is treated and wastewater treatment plants are not financially self-sustaining, resulting in uneven water quality [START_REF] Gilabert-Alarcón | Regulatory challenges for the use of reclaimed water in Mexico: a case study in Baja California[END_REF]. In Brazil, a country of more than 200 million inhabitants, the percentage of households with access to the wastewater treatment system does not exceed 50%, and a large part of the collected wastewater does not receive appropriate treatment before being discharged into rivers [START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF]. In Colombia, raw wastewater is sometimes discharged directly into surface waters in certain Colombian regions such as Florencia and Tumaco [START_REF] Botero-Coy | An investigation into the occurrence and removal of pharmaceuticals in wastewater Colombian[END_REF]. When untreated water is released, this contamination further reduces the availability of freshwater for domestic purpose and other uses, as well as damage to ecosystems is caused.

However, this is not just a domestic water problem. Indeed, treated industrial wastewater from the pharmaceutical, chemical, textile or metal industries, as well as water from agricultural activities including irrigation, livestock and aquaculture, can also contain a cocktail of substances, which end up in rivers. All these water uses can also pollute freshwater resources. Before being discharged, like municipal wastewaters, industrial effluents must nevertheless comply with regulations concerning a number of "conventional" substances such as metals and water parameters, namely suspended solids, chemical and biochemical oxygen demand, but organic substances are rarely registered in industrial wastewater [START_REF] Hernández-Padilla | Assessing wastewater treatment in Latin America and the Caribbean: enhancing life cycle assessment interpretation by regionalization and impact assessment sensibility[END_REF][START_REF] Gilabert-Alarcón | Regulatory challenges for the use of reclaimed water in Mexico: a case study in Baja California[END_REF].

The assessment of the occurrence of new contaminants in rivers is one of the major challenges for the scientific community. This task is important because there is a lack of information in most Latin American countries [START_REF] Hernández-Padilla | Assessing wastewater treatment in Latin America and the Caribbean: enhancing life cycle assessment interpretation by regionalization and impact assessment sensibility[END_REF][START_REF] Peña-Guzmán | Emerging pollutants in the urban cycle in Latin America: a review of the current literature[END_REF][START_REF] Starling | Occurrence, control and fate of contaminants of emerging concern in environmental compartments in Brazil[END_REF]. Unlike Europe and other regions, many Latin American countries do not have an established list of priority pollutants or laws controlling their production or release into the environment. However, regulations are beginning to evolve, particularly in Mexico, Colombia and Brazil, for example with regard to the treatment of municipal and industrial wastewater before discharge. Treatment plants and industries in Latin America do not have a formal structure to detect, assess, control and manage new compounds. Researchers and industrialists in Mexico, Colombia and Brazil draw on the experience of other developed countries in order to protect the aquatic environment of their respective regions, which have different conditions, environmental culture and pollutions levels [START_REF] Hernández-Padilla | Assessing wastewater treatment in Latin America and the Caribbean: enhancing life cycle assessment interpretation by regionalization and impact assessment sensibility[END_REF].

Pharmaceuticals, Personal Care Products and Pesticides in the Aquatic Environment in Mexico

Based on data of the Federal Agency of Consumer (PROFECO) of Mexico, this country is one of the main economies in Latin America, which has registered a strong growth in the personal care products market during the last decade, where around 40% of the demand is related to hair and skin care products. On the other hand, according to the Ministry of Health (Mexico), it is estimated that more than 80% of the Mexicans self-medicate, which means that they use drugs regardless medical prescription. As an example, diabetes is one of the main health issues in Mexico, and high pharmaceuticals consumption is associated to this disease. Unfortunately, similar to other countries, the uncontrolled use of drugs and personal care products, coupled to the discharge of untreated domestic wastewater or the inefficient removal of this type of substances in conventional wastewater treatment plants, can increase the contamination levels in the aquatic environment of various Mexican regions [START_REF] Gilabert-Alarcón | Regulatory challenges for the use of reclaimed water in Mexico: a case study in Baja California[END_REF][START_REF] Lesser | Survey of 218 organic contaminants in groundwater derived from the world's largest untreated wastewater irrigation system: Mezquital Valley, Mexico[END_REF][START_REF] Pérez-Alvarez | Determination of metals and pharmaceutical compounds released in hospital wastewater from Toluca, Mexico, and evaluation of their toxic impact[END_REF].

In some States, the reuse of wastewater has been implemented without integrative planning and assessment of the impact on ecosystems and public health [START_REF] Gilabert-Alarcón | Regulatory challenges for the use of reclaimed water in Mexico: a case study in Baja California[END_REF]. Despite emerging contaminants are rarely monitored in Mexico, the occurrence of pharmaceuticals and personal care products in effluents and surface waters has been investigated. With that aim, measurements of trimethoprim (0.11-0.15μg/L, 0.28-0.32μg/L), clarithromycin (0.37-0.45μg/L, 1.10-1.40μg/L), naproxen (6.2-6.74μg/L, 2.84-3.16μg/L), and diclofenac (0.25-0.34μg/L, 0.42-0.50μg/L) were determined in wastewater from Mexico City-Mezquital Valley (Pumping station "Gran Canal" and Emisor Profundo "El Salto"). The concentrations of these substances were found to be similar to levels reported for sewage in Europe, Japan, and USA. Levels of metoprolol (0.21-0.25μg/L) in water from the Gran Canal were comparative to the concentrations detected in wastewater in Switzerland (0.14-0.29μg/L), but these levels were higher than those found in sewage in Spain (< 0.005-0.09μg/L). The concentration of ibuprofen had been previously reported close to 0.3μg/L for both sampling points [START_REF] Siemens | Concentrations and mobility of human pharmaceuticals in the world's largest wastewater irrigation system, Mexico City-Mezquital Valley[END_REF]. [START_REF] Lesser | Survey of 218 organic contaminants in groundwater derived from the world's largest untreated wastewater irrigation system: Mezquital Valley, Mexico[END_REF] carried out analyses of untreated wastewater used for agricultural irrigation, from different points in Mezquital Valley (located in Central Mexico), reporting that from the group of 7 reproductive hormones and 118 pharmaceuticals measured, 3 hormones and 65 drugs were detected. Some examples include acetaminophen (39,900 ng/L), ciprofloxacin (1190 ng/L), sulfamethoxazole (5360 ng/L), oxytetracycline (134 ng/L), naproxen (11,800 ng/L) and metformin (82,900 ng/L).

In the same way, hospital wastewater from Toluca City (the capital city of the State of Mexico) was studied by the quantification of different pharmaceuticals, where antidiabetics (e.g., 1.92μg/L and 1.31μg/L for glibenclamide and metformin, respectively), β-blockers (0.20μg/L for atenolol and 2.02μg/L for metoprolol), β-lactams (3.77μg/L for penicillin G and 0.42μg/L for penicillin V), hormones (0.08μg/L for 17-β-estradiol), and anti-inflammatory drugs (0.59μg/L for diclofenac, 0.62μg/L for ibuprofen, 1.79μg/L for naproxen and 2.66μg/L for acetaminophen), were detected [START_REF] Pérez-Alvarez | Determination of metals and pharmaceutical compounds released in hospital wastewater from Toluca, Mexico, and evaluation of their toxic impact[END_REF].

Similarly, the presence of some emerging contaminants was also investigated in five effluents of domestic wastewater produced in the coastal zone of Cihuatlan, Jalisco (a State of Mexico on the edge of the Pacific Ocean) [START_REF] Arguello-Pérez | Ecotoxicological analysis of emerging contaminants from wastewater discharges in the coastal zone of Cihuatlán (Jalisco, Mexico)[END_REF]. These authors specified that diclofenac, ibuprofen and ketorolac were determined in all the analyzed effluents at concentration considered as "toxic", whilst estradiol was found in two of the effluents at concentrations that fall into a very toxic range. [START_REF] Díaz | A simple method for the simultaneous determination of pharmaceuticals and personal care products in river sediment by ultrasound-assisted extraction followed by solid-phase microextraction coupled with gas chromatography-mass spectrometry[END_REF] previously reported an analytic method for the detection of ibuprofen, 2-benzyl-4-chlorophenol, naproxen, triclosan, ketoprofen, diclofenac, bisphenol A and estrone in river sediments. Their analyses showed that sediment samples from the Tula River (Hidalgo, in central Mexico) had ibuprofen, naproxen and triclosan at concentrations in the order of ng/g. The authors remarked that the water sample with higher naproxen concentration (240 ng/L) was taken from the riverside where wastewater from Ixmiquilpan City was discharged.

Others monitoring studies exhibited the occurrence of pharmaceuticals in influent/effluent of the wastewater treatment plant "Acapantzingo" and surface water (Apatlaco River in Cuernavaca, the capital of the State of Morelos in south-central Mexico) [START_REF] Rivera-Jaimes | Study of pharmaceuticals in surface and wastewater from Cuernavaca, Morelos, Mexico: occurrence and environmental risk assessment[END_REF]. The total concentrations of pharmaceuticals were higher in surface water and influent wastewaters as compared to those detected in effluent wastewaters, showing the important role of wastewater treatment plants. [START_REF] Rivera-Jaimes | Study of pharmaceuticals in surface and wastewater from Cuernavaca, Morelos, Mexico: occurrence and environmental risk assessment[END_REF] indicated that the discharge of untreated wastewater increased the concentration of pharmaceuticals in the river, where naproxen (732-4880 ng/L), acetaminophen (354-4460 ng/L), diclofenac (258-1398 ng/L) and bezafibrate (286-2100 ng/L), were the most abundant.

Recently, [START_REF] Pérez-Coyotl | Polluted water from an urban reservoir (Madín dam, México) induces toxicity and oxidative stress in Cyprinus carpio embryos[END_REF] analyzed water samples from an urban reservoir (Madín dam, located in the municipalities of Naucalpan and Atizapán in the metropolitan area adjacent to Mexico City) that is a source of drinking water and represents an area for recreational activities, including carp fishing. Their results showed different concentrations of personal care products (especially sunscreens) and pharmaceuticals. As example, 2,2′,4,4′-tetrahydroxybenzophenone (13.7 ng/L), 2-ethylhexyl 4-(dimethylamino) benzoate (29 ng/L), 4-methylbenzylidine camphor (134 ng/L) and methyl benzotriazol (250 ng/L), antidiabetic agents glibenclamide and metformin (2148 ng/L and 9557 ng/L, respectively), and the analgesic acetaminophen (9156 ng/L) were detected. Hence, it is notably essential to implement a monitoring program of these emerging contaminants in drinking water sources of this region.

Another important problem in Mexico, as in other Latin American countries, is the presence of pesticides in water resources [START_REF] Parra | Distribution of pesticides and PCBs in sediments of agricultural drains in the Culiacan Valley, Sinaloa, Mexico[END_REF][START_REF] Arellano-Aguilar | Agrochemical loading in drains and rivers and its connection with pollution in coastal lagoons of the Mexican Pacific[END_REF]. The high availability and convenient cost of agrochemicals, as well as flexible environmental laws have led to an overuse of pesticides in Mexico, in order to satisfy the global demand of agricultural products. Nevertheless, residual agrochemicals in agricultural runoff are rarely monitored by farmers, and some of their leachates drain these pollutants to lakes or rivers (sources of drinking water), which eventually contaminate bays and coasts (Fig. 1.8) [START_REF] Osuna-Flores | Organochlorine pesticide residue concentrations in shrimps, sediments, and surface water from Bay of Ohuira, Topolobampo, Sinaloa, Mexico[END_REF][START_REF] Arellano-Aguilar | Agrochemical loading in drains and rivers and its connection with pollution in coastal lagoons of the Mexican Pacific[END_REF]. In particular cases, people of various villages are in contact with this type of hazardous leachates; furthermore, private wells for drinking water, which is untreated (used directly), are located close to agricultural fields [START_REF] Picos-Corrales | Environment-friendly approach toward the treatment of raw agricultural wastewater and river water via flocculation using chitosan and bean straw flour as bioflocculants[END_REF]. In this regard, some pesticides are regulated in Mexico by the Federal Commission for the Protection against Sanitary Risk, an organ of the Health Secretary of Mexico. Based on this environmental regulation (NOM-127-SSA1-1994), the maximum limits for the main organochloride pesticides for drinking water are: 30μg/L for 2,4-D (2,4-dichlorophenoxyacetic acid), 20μg/L for methoxychlor, 2μg/L for γ-lindane, 1μg/L for DDT (dichlorodiphenyltrichloroethane, total) and hexachlorobenzene, 0.2μg/L for chlordane, 0.03μg/L for heptachlor, aldrin and dieldrin (separated or combined).

Sinaloa is an example of an industrialized agricultural region in Northwestern Mexico that is characterized by a variety of crops and high production. In this State of Mexico, pesticides have been found in sediments of agricultural drainages [START_REF] Parra | Distribution of pesticides and PCBs in sediments of agricultural drains in the Culiacan Valley, Sinaloa, Mexico[END_REF]. From this assessment, concentrations of organochlorine compounds (15 substances) and organophosphorus compounds (8 substances) were within the ranges 0.1-20.19 ng/g and 0.03-1294 ng/g, respectively, being diazinon the compound with the highest concentration. Arellano-Aguilar et al. ( 2017) also reported that this industrialized agricultural region has a documented pesticides usage of 700 t/year, being at least 17 of the molecules classified as moderately to highly toxic.

With the same focus, Leyva-Morales et al. ( 2017) assessed the quality of river water from central Sinaloa (Humaya, Tamazula and Culiacan rivers) by monitoring residual pesticides. Their results showed that the following chemicals were present: lindane (0.0041-0.0104μg/L), endosulfan (0.0198-0.03601μg/L), heptachlor, dichlorodiphenyltrichloroethane (0.0525μg/L), diazinon (0.0211-0.0403μg/L), chlorpyrifos, methyl parathion, cyromazine (0.1961μg/L), permethrin (0.2351μg/L), ethion, carbofenothion, lambda cyhalotrine, pyrimicarb, aldrin (0.0099-0.1023μg/ L) and malathion. [START_REF] Leyva-Morales | Monitoring of pesticides residues in northwestern Mexico rivers[END_REF] suggested that pesticide contamination derived mainly from runoffs of polluted soil toward rivers.

Besides, the connection between agrochemical loading in drains/rivers and pollution in coastal lagoons of the Mexican Pacific has been studied [START_REF] Arellano-Aguilar | Agrochemical loading in drains and rivers and its connection with pollution in coastal lagoons of the Mexican Pacific[END_REF]. The authors indicated that the organochlorine chemicals were clearly accumulated in the coastal lagoons from the drains and rivers, with hexachlorocyclohexanes (organochlorine) showing the highest concentration. In another work regarding pesticides accumulation, levels of dichlorodiphenyltrichloroethane (∑DDTs ~0.6-137μg/kg) were quantified in sediments samples taken from Texcalac River in Tlaxcala (Mexico), exceeding the guidelines for protection of aquatic life according to the authors [START_REF] García-Nieto | Ecotoxicological assessment of sediment from Texcalac River and agricultural soil of riverside area, in Tlaxcala, Mexico[END_REF].

From the literature, Yucatan (southeastern Mexico) is a state with high levels of groundwater pollution, where different pesticides have been detected (3.2 mg/L for endrin, 10.86 mg/L for δ-lindane, 5.23 mg/L for γ-lindane, 6.53 mg/L for α-lindane and 12.54 mg/L for heptachlor) [START_REF] Polanco-Rodríguez | Impact of pesticides in karst groundwater. Review of recent trends in Yucatan, Mexico[END_REF]. This type of hazardous chemicals has been also identified in the drinking water source "Madín dam" of Naucalpan and Atizapan (Mexico), namely diazinon up to 12.592 ng/L and fenthion sulfoxide up to 2.465 ng/L [START_REF] Pérez-Coyotl | Polluted water from an urban reservoir (Madín dam, México) induces toxicity and oxidative stress in Cyprinus carpio embryos[END_REF]. Based on the current literature, it is recommended to increase the monitoring work regarding pesticides content in surface water in Mexico.

In addition to monitoring, examples related to the impact of emerging pollutants on human health and ecosystems in Mexico have also been reported. Researchers developed a strategy for the determination of some residual personal care product ingredients in hydroponic French lettuce from a local supermarket in Mexico (Cabrera-Peralta and Peña-Alvarez 2018). The results indicated that the use of wastewater to irrigate crops can result in contaminated food since the absorption by plants is favored in the presence of compounds with intermediate polarity. [START_REF] Martinez-Gomez | Lethal and sublethal effects of selected PPCPs on the freshwater rotifer, Plationus patulus[END_REF] previously assessed the effect of pharmaceuticals and personal care products on aquatic life using the rotifer Plationus patulus, which is a member of riverine food networks in Mexico. Results indicated that the continuous exposure to emerging contaminants could reduce rotifer population growth. Hence, the constant discharge of treated wastewater to aquatic ecosystems could represent a risk for the zooplankton community.

In another work, the toxicological risk of a hospital effluent from Toluca (the capital of the State of Mexico) was evaluated using two bioindicator species, i.e. Xenopus laevis and Lithobates catesbeianus [START_REF] Pérez-Alvarez | Determination of metals and pharmaceutical compounds released in hospital wastewater from Toluca, Mexico, and evaluation of their toxic impact[END_REF]). This research group suggested that the hospital effluents represent a latent risk for the ecological balance and diverse organisms, being necessary a prior treatment for the removal of the pharmaceuticals [START_REF] Pérez-Alvarez | Determination of metals and pharmaceutical compounds released in hospital wastewater from Toluca, Mexico, and evaluation of their toxic impact[END_REF].

Based on hazard quotients for pharmaceuticals detected in the Apatlaco River in Cuernavaca (the capital of the State of Morelos in south-central Mexico), [START_REF] Rivera-Jaimes | Study of pharmaceuticals in surface and wastewater from Cuernavaca, Morelos, Mexico: occurrence and environmental risk assessment[END_REF] found that contamination levels of this river could represent a risk for the aquatic ecosystem, due to the high concentrations of naproxen, ibuprofen, diclofenac and sulfamethoxazole. Similarly, experiments performed using samples from the drinking water source "Madín dam" (Naucalpan-Atizapán, State of Mexico) revealed that residual pharmaceuticals, personal care products and pesticides originated embryotoxicity, embryolethality, congenital abnormalities and oxidative stress on the common carp embryos. This was a rational explanation regarding the reduction in the population of Cyprinus carpio species of this ecosystem [START_REF] Pérez-Coyotl | Polluted water from an urban reservoir (Madín dam, México) induces toxicity and oxidative stress in Cyprinus carpio embryos[END_REF]. Also, in past years in the Bay of Ohuira (Topolobampo, a port on the Gulf of California in northwestern Sinaloa), the decrease in shrimp production was associated, among other causes, with the high coastal pollution by pesticides [START_REF] Osuna-Flores | Organochlorine pesticide residue concentrations in shrimps, sediments, and surface water from Bay of Ohuira, Topolobampo, Sinaloa, Mexico[END_REF]. In Chiapas (Southern Mexico), concentrations of organochlorine pesticides were found in a greater amount in cow's milk and forage than in water samples. Despite the content of contaminants was below the limits established by Mexican government, a monitoring program was recommended by the authors [START_REF] Murga | Organochlorine pesticide distribution in an organic production system for cow's milk in Chiapas, Mexico[END_REF].

It is also estimated that in Yucatan (southeastern Mexico) around 30% of the residents drink water from contaminated sources, and investigations reveled high levels of pesticides (7.352 mg/L for endosulfan I, 2.336 mg/L of 4,4′-dichlorodiphenyldichloroethane, 3.695 mg/L for aldrin and 1.434 mg/L for heptachlore) in the blood of women having cervical uterine cancer. Additionally, other studies showed the high levels of these chemicals in breast milk (18.436 mg/L for heptachlor epoxide and 2.10 mg/L for dieldrin) [START_REF] Polanco-Rodríguez | Impact of pesticides in karst groundwater. Review of recent trends in Yucatan, Mexico[END_REF].

In conclusion, Mexico is facing the problem of emerging substances in its aqueous compartments. This is not a novelty itself, but this problem is accentuated by the diversity of the substances found and the levels of quantified concentrations. Table 1.5 summarizes examples of contamination by emerging substances reported in water compartments in Mexico, comparing them with those reported by Columbian and Brazilian colleagues. It is necessary to mobilize all the stakeholders and the population to protect aquatic ecosystems in order to ensure the production of quality water. To achieve this goal, a thorough monitoring of surface waters is necessary and indispensable as part of a vast program at several spatial and temporal scales, not only at the national level but also as part of a more comprehensive water policy in collaboration with Mexico neighboring countries. In addition, attention should also be paid to treatment plants and their purification performance, as part of a more organizational water management at national and regional levels.

Emerging Contaminants in Colombian Rivers

Colombia is a country in South America with an area of Colombia bases its income mainly on the production of raw materials to export and to manufacture consumer products for the domestic market. Its main activities are the production of oil for exportation (fourth in Latin America and sixth in the continent) and mining, particularly carbon, gold, emeralds, sapphires and diamonds (Ministerio de Ambiente y Desarrollo Sostenible, 2016). The strongest industrial sectors in Colombia are petrochemicals, textiles, automobiles, and chemicals.

Colombia, like most countries in the World, is not immune to the problem of emerging compounds and Colombian developing regions are concerned [START_REF] Vidal | Validation of a gas chromatography/triple quadrupole mass spectrometry based method for the quantification of pesticides in food commodities[END_REF][START_REF] Barceló | Emerging contaminants from industrial and municipal waste[END_REF][START_REF] Ibáñez | Rapid screening of non-target organic pollutants in water by ultraperformance liquid chromatography coupled to time-oflight mass spectrometry[END_REF][START_REF] Ibáñez | Screening of antibiotics in surface and wastewater samples by ultra-high-pressure liquid chromatography to hybrid coupled quadrupole time-of-flight mass spectrometry[END_REF][START_REF] Klamerth | Degradation of emerging contaminants at low concentrations in MWTPs effluents with mild solar photo-Fenton and TiO 2[END_REF][START_REF] Teijón | Occurrence of emerging contaminants, priority substances (2008/105/EC) and heavy metals in treated wastewater and groundwater at Depurbaix facility (Barcelona, Spain)[END_REF][START_REF] Tobón ; Marulanda | Water pollution caused by pesticides in an área of Antioquia (in Spanish)[END_REF][START_REF] Gil | Emerging contaminants in waters: effects and possible treatments (in Spanish)[END_REF][START_REF] Díaz-Casallas | 2008-2017 Bogota river quality assessment based on the water quality index[END_REF][START_REF] Reichert | Emerging contaminants and antibiotic resistance in the different environmental matrices of Latin America[END_REF]. As in many other developing countries, Colombia's indiscriminate industrial growth has led to severe pollution of its waterbodies. Indeed, numerous studies have shown that several of its water sources are heavily contaminated, including by emerging contaminants. The sources of contamination are industrial, agricultural and domestic, the latter often uncontrolled. Once entered into the environment, chemicals and their metabolites can produce subtle effects on aquatic and terrestrial organisms, especially on the former since they are exposed to long-term continuous influx of wastewater effluents. Recently, [START_REF] Díaz-Casallas | 2008-2017 Bogota river quality assessment based on the water quality index[END_REF] proposed a comprehensive analysis of the water quality at the upper basin of the Bogotá River between 2008 and 2017, pointing out an insufficient quality of water. This study highlighted the necessity for further efforts on the continuous monitoring of Colombian rivers basins.

Indeed, Colombia is currently focusing its efforts on the detection and the quantification of emerging substances, in order to compile a list of priority substances adjusted to the needs and characteristics of Latin America. Research programs are also underway to provide recommendations for future monitoring, prevention and elimination programs for these chemicals. It is indeed important not only to monitor discharge waters from municipal treatment plants and industrial wastewaters but also to encourage the improvement of their systems and treatment techniques in order to achieve better removal efficiencies.

The list of substances that have been found in effluents from wastewater treatment plants, and consequently in Colombian waters (surface water, groundwater, etc.) is extremely varied, ranging from pharmaceuticals, hormones and steroids to surfactants, cosmetics and pesticides [START_REF] Hernández | Strategies for quantification and confirmation of multi-class polar products pesticides and transformation in water by LC-MS2 using triple quadrupole and hybrid quadrupole time-of-flight analyzers[END_REF][START_REF] Hernández | Use of time-of-flight mass spectrometry for large screening of organic pollutants in surface waters and soils from a rice production area in Colombia[END_REF][START_REF] Hernández | LC-QTOF MS screening of more than 1,000 licit and illicit drugs and their metabolites in wastewater and surface waters from the area of Bogotá, Colombia Bioanal[END_REF][START_REF] Vidal | Validation of a gas chromatography/triple quadrupole mass spectrometry based method for the quantification of pesticides in food commodities[END_REF][START_REF] Ibáñez | Rapid screening of non-target organic pollutants in water by ultraperformance liquid chromatography coupled to time-oflight mass spectrometry[END_REF][START_REF] Ibáñez | Screening of antibiotics in surface and wastewater samples by ultra-high-pressure liquid chromatography to hybrid coupled quadrupole time-of-flight mass spectrometry[END_REF][START_REF] Tobón ; Marulanda | Water pollution caused by pesticides in an área of Antioquia (in Spanish)[END_REF][START_REF] Bijlsma | Estimation of illicit drug use in the main cities of Colombia by means or urban wastewater analysis[END_REF][START_REF] Sarria-Villa | Presence of PAHs in water and sediments of the Colombian Cauca river during heavy rain episodes, and implications for risk assessment[END_REF][START_REF] Portilla | Intervention to rationalize use of losartan[END_REF][START_REF] Botero-Coy | An investigation into the occurrence and removal of pharmaceuticals in wastewater Colombian[END_REF][START_REF] Serna-Galvis | Degradation of seventeen contaminants of emerging concern in municipal wastewater effluents by sonochemical advanced oxidation processes[END_REF][START_REF] Reichert | Emerging contaminants and antibiotic resistance in the different environmental matrices of Latin America[END_REF]. These studies also helped to improve the understanding about the dynamics and behavior of the target compounds.

The substances most frequently found in Colombian water sources were pharmaceuticals such as antihypertensives, antibiotics, analgesics and psychiatric products, and illicit substances, e.g., cocaine and its main metabolite, heroine, and amphetamines (methamphetamine). They are detected at trace levels, usually between ng/L and μg/L, depending on the molecule. Raw wastewater from the cities of Bogotá, Medellín and Florencia contain levels of several pharmaceuticals above 1μg/L, while the concentrations for antibiotics are commonly above 5μg/L in raw hospital wastewater. A survey of the Latin American literature, including Colombian data, shows that all these substances are often identified and quantified by gas chromatography coupled to mass spectrometry [START_REF] Peña-Guzmán | Emerging pollutants in the urban cycle in Latin America: a review of the current literature[END_REF]. Continual improvements in analytical equipment and methodologies enable the determination of pharmaceuticals and their metabolites at lower and lower concentration levels in water samples and also in other environmental matrices.

Colombia is facing the problematic of the high use of pharmaceutical products and cosmetics (Fig. 1.9). Pharmaceuticals include antihypertensives (valsartan, irbesartan), antibiotics (ciprofloxacin, norfloxacin), anticonvulsants (carbamazepine), diuretics (furosemide), psychiatric products (gabapentin, benzodiazepine derivatives, antiepileptics), and psychoactive agents (hallucinogens). Benzophenones (benzophenone-1, benzophenone-2, benzophenone-3, benzophenone-4), parabens (methylparaben, ethylparaben, butylparaben, propylparaben), triclosan and bisphenols are examples of cosmetic ingredients considered as endocrine disruptors. Among these substances, antihypertensives (valsartan, irbesartan), antibiotics (ciprofloxacin, norfloxacin) and endocrine disruptors are of great concern and their hazardous effects are already reported (Darbre 2015; [START_REF] Gee | Considerations of endocrine disruptors in drinking water (chapter 18)[END_REF]. Triclosan is also a substance of concern. This hydrophobic substance can accumulate in fatty tissues, such as fish and human samples (urine, breast milk and serum). Moreover, triclosan has been shown to have toxic effects in aquatics organisms at environmental concentrations and its degradation products can be more toxic and persistent than the parent compound [START_REF] Kosma | Investigation of PPCPs in wastewater treatment plants in Greece: occurrence, removal and environmental risk assessment[END_REF][START_REF] Juliano | Cosmetic ingredients as emerging pollutants of environmental and health concern. A mini-review[END_REF][START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF][START_REF] Montagner | Ten years-snapshot of the occurrence of emerging contaminants in drinking, surface and ground waters and wastewaters from São Paulo State, Brazil[END_REF]).

A first typical example is the presence of losartan, an antihypertensive widely used in Colombia [START_REF] Portilla | Intervention to rationalize use of losartan[END_REF][START_REF] Serna-Galvis | Degradation of seventeen contaminants of emerging concern in municipal wastewater effluents by sonochemical advanced oxidation processes[END_REF]. Another typical example is ciprofloxacin that is among the top five most common antibiotics prescribed in Colombian hospitals. [START_REF] Botero-Coy | An investigation into the occurrence and removal of pharmaceuticals in wastewater Colombian[END_REF] and Serna-Galvis et al. ( 2019) have reported its frequent presence in hospital effluents. However, the load from hospital wastewater varied from study to study. Another problem is the presence of endocrine disruptors, which are capable of blocking and altering every hormonal function, disrupt the endocrine system. Endocrine disruptors are compounds that mimic the hormones produced by living organisms and interfere with various functions (Darbre 2015). These chemical compounds include the natural (17-β-estradiol) and synthetic (17-α-ethynylestradiol) hormones used in birth control pills, fertility treatments and hormone replacement therapy. All these endocrine disruptors end up in water via domestic, industrial and/or hospital discharges. However, conventional municipal wastewater treatment plants are not designed to deal with these substances, and consequently such molecules and their metabolites can reach the aquatic environment. Endocrine disrupting effects such as intersexuality and reproductive disorders have been reported in fish and other aquatic organisms living downstream from wastewater treatment plant outfalls [START_REF] Vajda | Reproductive disruption in fish downstream from an estrogenic wastewater effluent[END_REF][START_REF] Gagné | Evidence of feminization in wild Elliptio complanata mussels in the receiving waters downstream of a municipal effluent outfall[END_REF][START_REF] Tetreault | Intersex and reproductive impairment of wild fish exposed to multiple municipal wastewater discharges[END_REF]. Cocaine is a highly consumed illicit drug in populated Colombian cities such as Bogotá, and consequently, its main metabolite (benzoylecgonine) has a high prevalence in wastewaters [START_REF] Bijlsma | Estimation of illicit drug use in the main cities of Colombia by means or urban wastewater analysis[END_REF][START_REF] Hernández | LC-QTOF MS screening of more than 1,000 licit and illicit drugs and their metabolites in wastewater and surface waters from the area of Bogotá, Colombia Bioanal[END_REF][START_REF] Serna-Galvis | Degradation of seventeen contaminants of emerging concern in municipal wastewater effluents by sonochemical advanced oxidation processes[END_REF]. [START_REF] Bijlsma | Estimation of illicit drug use in the main cities of Colombia by means or urban wastewater analysis[END_REF] conducted for the first time a wastewater-based epidemiology in Colombia, reporting that cocaine was the most consumed illicit drug, particularly in Medellin (department of Antioquia). Benzoylecgonine, a cocaine metabolite, exceeded 4000 ng/L in all samples from wastewater treatment plants. Amphetamines were also found in all samples at concentrations between 12 ng/L and 68 ng/L [START_REF] Bijlsma | Estimation of illicit drug use in the main cities of Colombia by means or urban wastewater analysis[END_REF]. Illicit substances, together with pharmaceuticals, are commonly measured in Colombian effluents as both groups of substances are not completely removed with conventional treatments [START_REF] Serna-Galvis | Degradation of seventeen contaminants of emerging concern in municipal wastewater effluents by sonochemical advanced oxidation processes[END_REF].

Another important issue is the presence of pesticides, such as glyphosate, dichlorodiphenyltrichloroethane (DDT), parathion and clofibric acid, in water, since Colombia is a major agricultural country that uses phytosanitary products. A typical example is the presence of glyphosate used to protect illicit crops. The frequent detection of this substance suggests that it is a widespread environmental contaminant. Another typical example is the insecticide DDT which has well know adverse health consequences, namely an established link with malformations in newborns. Studies have also shown significant impacts on fish and reptiles (deformities, reduced fertility, and abnormal behavior).

There are also industrial products such as phthalates, bisphenol A and its analogues (bisphenol F and bisphenol S) used in the production of resins and plastics, paints/lacquers and binding materials, or cleaning agents (nonylphenol). Another example is triclosan used as a broad spectrum antibacterial agent into many consumer products and as preservative in products of domestic use. It is also found in cosmetics, textiles and antibacterial fibers. These substances have been identified and quantified in industrial wastewaters and in rivers.

In Colombia and in other Latin America countries, the situation is worrying not only from a water pollution point of view but also from a health point of view, with the appearance of resistance phenomena for certain bacteria. Antibiotics are antimicrobial drugs that kill or reduce the growth of bacteria. They have been used in large quantities for several decades around the World and antibiotic resistance of pathogens has been for long a focus of research in clinical settings and, more recently, in environmental research. Incorrect use of antibiotics increases resistance to them, a process called antimicrobial resistance, the antibiotic being ineffective on a bacterial infection. The more antibiotics are consumed, the greater the risk of developing resistant bacteria [START_REF] García | A review of emerging organic contaminants (EOCs), antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs) in the environment: increasing removal with wetlands and reducing environmental impacts[END_REF]. One widely reported case is that of Staphylococcus aureus, which has developed resistance to methicillin (MRSA). This bacterium is a clear example of hospital infections originated when a certain patient stays in a hospital for long periods of time, creating a big problem in terms of hospital hygiene. There are three main routes of entry of antibiotics into freshwater: (1) effluents from wastewater treatment plants, (2) chemical manufacturing plants, and (3) livestock, agricultural and aquaculture sites. Indeed, antibiotics can bypass water treatment processes and end up directly in the environment. They are detected in Colombian rivers at very low concentrations and are diluted more than a million times compared to concentrations in the human body. However, these residual concentrations are highly likely to generate antimicrobial resistance, having direct and indirect effects on the microbial component of aquatic communities. Indeed, even at low concentrations, these antibiotics could have significant consequences for ecosystems and human health.

In conclusion, the presence of emerging substances in Colombian waters is a concern that is becoming increasingly important in society. The demand for water, whether for domestic, agricultural or industrial use, is constantly increasing, with the consequences of water pollution and ecosystem degradation, as a significant amount of wastewater is either untreated or poorly treated. This scenario is complicated by a climate context that is affecting the predictability of our most precious resource. All water stakeholders are concerned by this issue and mobilized. There is a growing consensus that the challenges can be tackled by adopting an integrated approach for water resources management. In particular, special efforts need to be made in the operation of municipal wastewater treatment plants and in the protection of the ecosystems and water resources.

Analysis of Emerging Contaminants in Brazilian Water Resources

As in Mexico and Colombia, the presence of the same vast group of emerging contaminants (pharmaceuticals, personal care products and cosmetics, industrial substances and pesticides) in Brazil's water resources, including rivers, lakes, drinking water reservoirs and tap water, has been reported at the same orders of magnitude of concentrations, showing that the conventional wastewater treatments are not effective for their removal, even in regions that have adequate sanitation. Indeed, numerous studies indicated that the conventional applied wastewater treatments are not efficient enough to remove these substances from wastewater and sludge, and as a result they find their way into the environment [START_REF] Barbosa | Pesticides in drinking water -The Brazilian monitoring program[END_REF][START_REF] Campanha | A 3-year study on occurrence of emerging contaminants in an urban stream of São Paulo State of Southeast Brazil[END_REF][START_REF] Albuquerque | Pesticides in Brazilian freswaters: a critical review[END_REF][START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF][START_REF] Caldas | Occurrence of pesticides and PPCPs in surface and drinking water in Southern Brazil: data on 4-year monitoring[END_REF][START_REF] Starling | Occurrence, control and fate of contaminants of emerging concern in environmental compartments in Brazil[END_REF].

The collection, treatment and reuse of wastewater from households and industry, the reduction of diffuse pollution and the improvement of water quality are major challenges for Brazilian water stakeholders. Freshwater quality is indeed under threat. Its pollution is widespread and increasing in many regions. In Brazil, regulations concerning emerging contaminants in both natural waters and drinking water require a commitment among researchers and regulatory authorities, since this issue has not been considered as a priority by the government [START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF].

The substances that have been analyzed in Brazilian waters include mainly, hormones, antibiotics, endocrine disruptors, caffeine (as licit drug), illicit drugs (methamphetamine, cocaine, heroin), industrial compounds (bisphenols, triclosan), and pesticides. Among them, pesticides in particular have been monitored, as Brazil is the World's largest consumer of herbicides, fungicides and insecticides [START_REF] Barbosa | Pesticides in drinking water -The Brazilian monitoring program[END_REF][START_REF] Albuquerque | Pesticides in Brazilian freswaters: a critical review[END_REF][START_REF] Caldas | Occurrence of pesticides and PPCPs in surface and drinking water in Southern Brazil: data on 4-year monitoring[END_REF][START_REF] Starling | Occurrence, control and fate of contaminants of emerging concern in environmental compartments in Brazil[END_REF], which means that these substances may end up in the environment, especially in aquatic systems and reservoirs used for drinking water production. There are 381 active ingredients authorized by the Brazilian Ministry of Agriculture for pesticides used on crops and 1670 formulated plant protection products in the market [START_REF] Albuquerque | Pesticides in Brazilian freswaters: a critical review[END_REF]). Brazil has regulations on the use of pesticides and their presence in water. For example, the Brazilian drinking water norm (Ordinance 2914/2011 of the Ministry of Health) includes 64 chemical substances, of which 27 are pesticides that must be monitored every 6 months. However, this number represents <10% of the current pesticide active ingredients approved for use in the country [START_REF] Barbosa | Pesticides in drinking water -The Brazilian monitoring program[END_REF]. Of the 27 pesticides, 21 are banned in Europe due to the risks they offer to health and the environment. A comprehensive review on the presence of pesticides in Brazilian freshwaters was published by [START_REF] Albuquerque | Pesticides in Brazilian freswaters: a critical review[END_REF]. They reported that data in peer-reviewed literature are scarce and often incomplete, concluding that, whitout the implementation of a nationwide pesticide freshwater monitoring program and a clear definition of proper water quality standards, it is not possible to evaluate the risks posed by pesticides to the aquatic life in Brazil.

Among the most widely used pesticides in Latin America, glyphosate and atrazine occupy prominent positions as the best-selling active ingredients in Brazil (Brazil 2011; [START_REF] Barbosa | Pesticides in drinking water -The Brazilian monitoring program[END_REF][START_REF] Marin | Synthesis and characterization of graphene oxide functionalized with MnFe 2 O 4 and supported on activated carbon for glyphosate adsorption in fixed bed[END_REF]. Since its introduction as an herbicide active ingredient in 1971, glyphosate became and remains the market leading herbicide worldwide (glyphosate-based formulations are mainly represented by Roundup). The limit of glyphosate in drinking water in Brazil is 0.5μg/L (Brazil 2011; [START_REF] Barbosa | Pesticides in drinking water -The Brazilian monitoring program[END_REF], while in Europe only 0.1μg/L is permitted (0.9μg/L for World Health Organization, 0.8μg/L for Canada). The 0.1μg/L value is also the maximal residue level of glyphosate in European surface and ground water. The maximum contaminant level in the U.S. in drinking water is 700μg/L (sum of glyphosate and its residues) and the health-based guideline value in Australia is 1000μg/L [START_REF] Székács | Re-registration challenges of glyphosate in the European Union[END_REF]. The contamination of the environment by glyphosate is worrying since it impairs enzymatic activity, causes cytoxicity and DNA data in human cells [START_REF] Marin | Synthesis and characterization of graphene oxide functionalized with MnFe 2 O 4 and supported on activated carbon for glyphosate adsorption in fixed bed[END_REF].

In drinking and surface waters, acceptable limit for atrazine (herbicide of the triazine class) and methyl parathion (organophosphate insecticide) are 9 and 2μg/L, respectively (Ordinance 2914/2011 of the Ministry of Health). These limits are based on toxicological and neurotoxicological trials, but they do not take into account possible estrogenic effects that atrazine can cause when human and wildlife are chronically exposed to low concentrations [START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF]. In Canada, the maximum acceptable concentration for atrazine in drinking water is 5μg/L (this value is applicable to the sum of atrazine and its metabolites) while for the United States Environmental Protection Agency, the maximum concentration in water is 3μg/L. In the European Union, a limit of 0.1μg/L has been set for all pesticide residues in drinking water and groundwater. This value of 0.1μg/L for each substance represents a standard for water quality, not for the health risk. If more than one pesticide is found in drinking water, the sum of all pesticides has a legal limit of 0.5μg/L (source: French Agency for Food, Environmental and Occupational Health & Safety). [START_REF] Sodré | Occurrence of emerging contaminants in Brazilian drinking waters: a sewage-to-tap issue[END_REF] investigated the occurrence of endocrine disruptors in drinking water of the city of Campinas. Six emerging contaminants (stigmasterol, cholesterol, bisphenol A, caffeine, estrone, and 17-β-estradiol) were found in twelve samples. Estrone and 17-β-estradiol were detected only during the dry season, with concentrations below quantification limits. Stigmasterol showed the highest average concentration (0.34 ± 0.13μg/L), followed by cholesterol (0.27 ± 0.07μg/L), caffeine (0.22 ± 0.06μg/L), and bisphenol A (0.16 ± 0.03μg/L). Alarmingly, the level of bisphenol A detected in drinking water (0.0005μg/L) was higher than the average effluent from effluent treatment plants (0.00002μg/L) [START_REF] Sodré | Occurrence of emerging contaminants in Brazilian drinking waters: a sewage-to-tap issue[END_REF]. Ten years later, Peña-Guzmán et al. ( 2019) also reported similar levels of concentrations. [START_REF] Sodré | Occurrence of emerging contaminants in Brazilian drinking waters: a sewage-to-tap issue[END_REF] concluded that, in Campinas, where surface drinking water supplies receive large amounts of raw sewage inputs, the emerging contaminants levels in drinking waters were higher than median values compiled for drinking and finished water samples around the World. [START_REF] Montagner | Spatial and seasonal variations of pharmaceuticals and endocrine disruptors in the Atibaia River, Sao Paulo State (Brazil)[END_REF] also reported that among endocrine disruptors, bisphenol A (a compound used as a manufacturing intermediate) is distinguished by its widespread presence in the environment. In the State of São Paulo, this substance was detected in all surface water sampling campaigns with concentrations between 204 and 13,016 ng/L [START_REF] Montagner | Spatial and seasonal variations of pharmaceuticals and endocrine disruptors in the Atibaia River, Sao Paulo State (Brazil)[END_REF].

A special substance in Latin America is caffeine. It is consumed by people of all ages, cultures and socio-economic status [START_REF] Campanha | A 3-year study on occurrence of emerging contaminants in an urban stream of São Paulo State of Southeast Brazil[END_REF][START_REF] Sodré | Seasonal and spatial distribution of caffeine, atrazine, atenolol and DEET in surface and drinking waters from the Brazilian Federal District[END_REF][START_REF] Peña-Guzmán | Emerging pollutants in the urban cycle in Latin America: a review of the current literature[END_REF][START_REF] Starling | Occurrence, control and fate of contaminants of emerging concern in environmental compartments in Brazil[END_REF]). As caffeine is present in everyday beverages such as coffee, tea, chocolate and cola drinks, a large amount of caffeine waste is generated, which enters the aquatic environment. Many drugs also contain caffeine, namely analgesics, antihistamines, diet pills, cold remedies, and stimulants of psychophysical activity. [START_REF] Campanha | A 3-year study on occurrence of emerging contaminants in an urban stream of São Paulo State of Southeast Brazil[END_REF] reported a three-year study on the occurrence of pharmaceuticals and hormones in surface waters of a central urban region of São Paulo State of Southeast Brazil (the Monjolinho River in São Carlos). The most frequently detected compounds at highest concentrations were caffeine, paracetamol, and atenolol (maximum concentrations 129.585μg/L, 30.421μg/L, and 8.199μg/L, respectively), while the hormones estrone and 17-β-estradiol were the least detected, at levels up to 0.0148 ng/L. The results also showed that there was an increasing trend in concentrations of most of the compounds along the river course, especially downstream of the river where there are discharges of both wastewater treatment plant effluent and raw sewage from a particular region of São Carlos city. The concentrations of contaminants were higher during dry periods as a result of the decline in the water levels. A decrease of concentrations occurred near the river mouth at different extents for each compound, being high for caffeine and atenolol and very low for carbamazepine and diclofenac.

The first nationwide survey of emerging contaminants in Brazilian waters has been published by [START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF]. One hundred drinking water samples were investigated in 22 Brazilian State capitals during two campaigns between July and September of 2011 and 2012. In addition, seven source water samples from two of the most populous regions of the country were evaluated. The analytical monitoring showed that caffeine, triclosan, atrazine, phenolphthalein and bisphenol A were found in at least one of the samples collected in the two sampling campaigns. Caffeine and atrazine were the most frequently detected substances in both drinking and source water, in agreement with the results published by [START_REF] Campanha | A 3-year study on occurrence of emerging contaminants in an urban stream of São Paulo State of Southeast Brazil[END_REF]. Caffeine concentrations in drinking water ranged from 1.8 ng/L to values above 2.0μg/L while source-water concentrations varied from 40 ng/L to approximately 19μg/L. The frequency of detection of caffeine corresponded to 93%, corresponding to a higher frequency than those found in similar Spanish and Chinese studies (<88% in the two cases). For atrazine, concentrations were found ranging from 0.002 to 0.006μg/L in drinking water and at concentrations of up to 0.15μg/L in source water. The levels of atrazine were between two and three orders of magnitude below the maximum limit established by the Brazilian regulations (2.0μg/L is the authorized value in drinking and surface water). Atrazine was found in 75% of the drinking water samples collected in both campaigns. Only two other substances, triclosan and phenolphthalein, were detected in drinking water samples. Emerging contaminants such as pharmaceuticals, hormones, and industrial products were not detected in the samples. Caffeine, atrazine, and bisphenol were detected in all seven surface samples. The highest concentrations of caffeine and bisphenol A detected were 18.828μg/L and 0.011μg/L in a reservoir connected to the Rio Grande River. [START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF] concluded that in both drinking and source waters, caffeine reached concentration values from a few ng/L to μg/L, depending on the region of collection. The detection frequency of caffeine in drinking water was higher than other values reported in the literature. Its widespread presence in samples of treated water (detected in 93% of samples) suggested the presence of domestic sewage in the source water, considering that caffeine is a compound of anthropogenic origin, exhibiting great residence time in the environment and low susceptibility to degradation. Caffeine can be proposed as an indicator of contamination by sewage [START_REF] Campanha | A 3-year study on occurrence of emerging contaminants in an urban stream of São Paulo State of Southeast Brazil[END_REF][START_REF] Machado | A preliminary nationwide survey of the presence of emerging contaminants in drinking and source waters in Brazil[END_REF].

More recently, [START_REF] Montagner | Ten years-snapshot of the occurrence of emerging contaminants in drinking, surface and ground waters and wastewaters from São Paulo State, Brazil[END_REF] summarized the results of 10 years of analyses carried out in the State of São Paulo that has one of the highest population densities in Brazil and intense agricultural and industrial activities. In this work, 58 compounds (9 hormones, 14 pharmaceuticals and personal care products, 8 industrial compounds, 17 pesticides and 10 illicit drugs) were determined in 708 samples between 2006 and 2015. Samples were collected in 13 cities in the State of São Paulo (drinking water), in 10 rivers (surface waters) and 4 reservoirs, and in 5 municipal wastewater treatment plants (wastewaters). The frequency of detection of each substance strongly varied among samples. The average concentration for the synthetic contraceptive 17-α-ethynylestradiol was 777 ng/L. The highest frequencies of detection in surface water were in the following order: caffeine (97%), atrazine (69%), triclosan (43%), estriol (31%), estrone (28%) and testosterone (13%). Caffeine levels varied from 19 to 127,000 ng/L, reflecting the differences between sampling points according to their anthropogenic impact, similar to the results reported by [START_REF] Campanha | A 3-year study on occurrence of emerging contaminants in an urban stream of São Paulo State of Southeast Brazil[END_REF] in the Monjolinho River, the main water body of São Paulo. Bisphenol A was quantified in 145 samples in a wide range of concentrations, between 2 and 13,016 ng/L. Cocaine ant its metabolite (benzoylecgonine) were detected in 53% (average concentration: 10 ng/L) and 84% (average concentration: 133 ng/L) of the samples, respectively. For drinking water (289 samples between 2007 and 2015), bisphenol A was the most frequently analyzed substance (258 samples, average concentration 23 ng/L and a maximum concentration of 178 ng/L) followed by caffeine (231 samples, average concentration of 548 ng/L), testosterone (215 samples, average concentration of 3 ng/L), 4-n-nonylphenol (189 samples, average concentration of 114 ng/L), triclosan (186 samples with concentrations ranging from 2 to 37 ng/L), and atrazine (179 samples, average concentration of 36 ng/L). All hormones were analysed in more than 100 samples, but the frequencies of detection were between 0 and 4%, the maximum concentration being 125 ng/L for estriol. Other substances such as dioctylphthalate and octylphenols were found in drinking water. From the 33 groundwater samples collected, the most prevalent substance was atrazine (86% of samples 6/7) followed by caffeine (55%, 17/31) and bisphenol A (50%, 16/32). Finally, a preliminary risk assessment for aquatic life protection identified potential risks for caffeine, paracetamol, diclofenac, 17-α-ethynylestradiol, 17-β-estradiol, estriol, estrone, testosterone, triclosan, 4-n-nonylphenol, bisphenol A, atrazine, azoxystrobin, carbendazim, fipronil, imidacloprid, malathion and tebuconazole. As expected, raw wastewaters had high levels of concentrations, with the highest values reported for caffeine, benzoylecgonine and cocaine. Peña-Guzmán et al. ( 2019) reported similar findings. However, even after treatment, some emerging contaminants were still detected at relatively high concentrations in the treated wastewaters. [START_REF] Montagner | Ten years-snapshot of the occurrence of emerging contaminants in drinking, surface and ground waters and wastewaters from São Paulo State, Brazil[END_REF] suggested that the wastewater treatment technology used in São Paulo State (Brazil) was not effective for the elimination of most of the target compounds. [START_REF] Campanha | A 3-year study on occurrence of emerging contaminants in an urban stream of São Paulo State of Southeast Brazil[END_REF] also indicated that the main source of emerging contaminants in the river was related to the discharges from wastewater treatment plants. Drinking water criteria were available only for 22 compounds of those studied by [START_REF] Montagner | Ten years-snapshot of the occurrence of emerging contaminants in drinking, surface and ground waters and wastewaters from São Paulo State, Brazil[END_REF] and for those substances no adverse effects were expected at the concentrations found, except for 17-β-estradiol and atrazine. [START_REF] Montagner | Ten years-snapshot of the occurrence of emerging contaminants in drinking, surface and ground waters and wastewaters from São Paulo State, Brazil[END_REF] concluded that, among the 58 studied contaminants, caffeine, estrone, 17-α-ethynylestradiol, 17-β-estradiol, bisphenol A, atrazine, carbendazim, fipronil, malathion and imidacloprid were underlined as substances of priority concern, due to the high frequency of detection above water quality criteria. Another important conclusion was the fact that caffeine and benzoylecgonine were pertinent anthropogenic indicators, especially for regions highly inhabited and with poor sanitation structure. Since the cocaine metabolite can persist in the aquatic environment even after 2 weeks from the discharge, this substance may be a reliable marker of contamination of surface water and also for drinking water. [START_REF] Caldas | Occurrence of pesticides and PPCPs in surface and drinking water in Southern Brazil: data on 4-year monitoring[END_REF] studied the presence of 33 pesticides in surface and drinking water in Southern Brazil (data of four-year monitoring; 48 samples) and reported that 30 substances were identified and quantified, whereas four compounds (tebuconazole, atrazine, azoxystrobin, clomazone) were identified in more than half of the samples. Five class of pesticides, i.e., triazines, triazoles, carbamates, strobilurins and imidazolinones, were identified. Among them, the herbicide atrazine was the most frequently detected pesticide, with concentrations ranging from 0.005μg/L to 0.049μg/L in drinking water and from 0.005μg/L to 0.037μg/L in surface water. In this study, atrazine was identified as a priority substance amongst those that pose a significant risk to the aquatic environment. The authors hypothesized a relationship with agricultural activities because atrazine is widely used in Brazil as a weed-killer in the cultivation of crops (rice, soybeans, sugarcane, corn). Other pesticides detected in the whole 4-year monitoring period were the fungicide azoxystrobin (concentrations ranging from 0.041μg/L to 0.233μg/L and from 0.1μg/L to 0.192μg/L in surface and drinking water, respectively), the herbicide clomazone (identified in more than 50% of the samples at concentrations up to 0.164μg/L) and the triazole molecules such as cyproconazole, difenoconazole, epoxiconazole, propiconazole and tebuconazole (identified in more than 80% of the samples at concentrations up to 0.46μg/L). Triazole substances are used not only as fungicides in agriculture and as biocides but also as antifungal agents in human and veterinary pharmaceuticals. [START_REF] Caldas | Occurrence of pesticides and PPCPs in surface and drinking water in Southern Brazil: data on 4-year monitoring[END_REF] concluded that the concentrations detected (ranging from 0.004 to 1μg/L) were of the same order of magnitude as those detected in other regions of Brazil. The concentrations of the target pesticides detected in drinking water in the city of Rio Grande were below the limits established by the Brazilian legislation and by the World Health Organization. However, considering the values established by the European Union for individual pesticides in drinking water of 0.1μg/L, the maximum values detected for some pesticides (e.g., azoxystrobin, cyproconazole, clomazone, quinclorac and tebuconazole) exceeded this limit.

Numerous Brazilian studies come to the conclusion that, in many Brazilian regions that suffer from poor sanitary conditions, there is an urgent need to study the occurrence of emerging contaminants in natural waters. Those reports show the importance of continuous monitoring of this type of substances and other water parameters for proper water management. The use of pesticides should be minimized, and if necessary, agricultural practices should be modified. Another important action should focus on improving the treatment processes applied in the municipal wastewater treatment plants [START_REF] Sodré | Seasonal and spatial distribution of caffeine, atrazine, atenolol and DEET in surface and drinking waters from the Brazilian Federal District[END_REF][START_REF] Montagner | Ten years-snapshot of the occurrence of emerging contaminants in drinking, surface and ground waters and wastewaters from São Paulo State, Brazil[END_REF][START_REF] Peña-Guzmán | Emerging pollutants in the urban cycle in Latin America: a review of the current literature[END_REF][START_REF] Caldas | Occurrence of pesticides and PPCPs in surface and drinking water in Southern Brazil: data on 4-year monitoring[END_REF][START_REF] Starling | Occurrence, control and fate of contaminants of emerging concern in environmental compartments in Brazil[END_REF].

In conclusion, the extent of industrial pollution is not yet well known in Latin America, as discharges are poorly monitored and rarely aggregated at the national level. Although some domestic and industrial wastewater is treated on-site, few data are available and aggregated for national and regional assessments, unlike in Europe. Many countries lack the capacity to collect and analyze the data needed for a comprehensive assessment. Reliable monitoring of water quality is nevertheless essential to guide investment priorities. It is also important for assessing the status of aquatic ecosystems and the need to protect and/or restore them.

Conclusion

Emerging substances are a diverse group of chemical and biological agents, which possible consequent health and ecological effects are of increasing concern. Many chemical substances are non-biodegradable or refractory, toxic or carcinogenic, some are regulated, and others have been banned for several years but are still found in the environment. As described in this chapter, emerging substances are present in water resources around the world, from all the 5 continents, with specific examples given from China, Portugal, Mexico, Colombia and Brazil, raising concerns for human health and the environment. The list of substances and products is exceptionally long: pesticides, pharmaceuticals, hormones and steroids, cosmetics, personal care products, illicit drugs, surfactants, cleaning products, industrial formulations and chemicals, food additives, food packaging, metalloids, rare earth elements, nanomaterials, microplastics and pathogens. Due to insufficient chemical treatment abatement, the discharge of effluents from municipal wastewater treatment plants is an important route for the appearance of chemical substances in the aquatic environment. One of the levers for action concerns the improvement of the operation of wastewater treatment plants, such as, for example, the installation of tertiary treatment systems in order to move towards zero pollution discharge. However, attention must be paid to all sources of water pollution, such as those resulting from the intensive use of pesticides.

We are all both concerned and worried about water pollution. The multifaceted pollution resulting from our lifestyles and consumption patterns and the worrying synergies that can occur in wastewater due to the multiplicity of pollutants (pathogens, emerging substances, metals, etc.) are major threats to this vital element that is water, with consequences also for the environment and human health. However, the behavior of emerging substances in the environment and their effects on all living organisms remain largely unknown. We must (continue) to mobilize to protect this resource.

Fig. 1 . 1

 11 Fig. 1.1 Classification of emerging contaminants and issues of concern in water compartments

Fig. 1 . 2

 12 Fig. 1.2 Accumulation of plastic debris on a shoreline in France. (Source: Florence Carreras, INRA, France)

Fig. 1 . 3

 13 Fig. 1.3 Relationship between gas chromatography/mass spectrometry (GC/MS) and different interfaces of liquid chromatography/mass spectrometry (LC/MS) (APPI atmospheric pressure photoionization, APCI atmospheric pressure chemical ionization, source: Eric Carmona, Leipzig, Germany)

Fig. 1 . 4

 14 Fig. 1.4 Different microplastic forms from the Elber River, Germany: (a) white spheres; (b) blue, red, white and black fragments and one white sphere; (c) light blue film; and (d) brown and black fibers. (Source: Friederike Stock, Koblenz, Germany)

Fig. 1 . 5

 15 Fig. 1.5 The estimated current end use of rare earth elements. (Adapted from U.S. Geological Survey, USGS 2020, Reston, Virginia)

Fig. 1 . 6

 16 Fig. 1.6 Average concentrations of various persistent organic pollutants in the Chinese Taihu lake ecosystem (TBBPA tetrabromobisphenol A, PCDD/Fs polychlorinated dibenzo-p-dioxins and dibenzofurans, PCBs polychlorinated biphenyls, PBDEs polybrominated diphenyl ethers, PAHs polycyclic aromatic hydrocarbons, OCPs organochlorine pesticides, HBCD hexabromocyclododecane, DDT dichlorodiphenyltrichloroethane, DDTs DDT-related compounds)

Fig. 1 . 7

 17 Fig. 1.7 River pollution by emerging contaminants and related challenges for their management. Ave River (left) and Leça River (right). (Source: Ana Rita Lado Ribeiro, Porto, Portugal)

Fig. 1 . 8

 18 Fig. 1.8 Contamination sequence involving river pollution in Sinaloa from agricultural wastewater (Sinaloa is an important agricultural region of Mexico; source: Lorenzo A. Picos-Corrales, Sinaloa, Mexico)

Fig. 1 . 9

 19 Fig. 1.9 Example of emerging contaminants in Colombian Rivers. (Source: Juan Carlos Moreno-Piraján, Bogotá, Colombia)

Table 1 .2

 1 Occurrence of nonylphenol and octylphenol in aquatic environment (concentration in water in ng/L; concentration in sediment in ng/g dry weight; detection frequency in %)

	Region,			Concentration	Sample	Detection
	Country	Matrix	Compound	range (mean)	number	frequency References
	Yinma	River water 4-Nonylphenol	14.13-392.41	51	100%	Sun et al.
	River Basin,			(71.77)			(2019)
	China
	Yinma	River	4-Nonylphenol	1.33-98.44	51	100%	Sun et al.
	River Basin,	sediment		(30.68)			(2019)
	China
	Bahe River,	River water 4-tert-	<1.2-126.0	10	100%	Wang et al.
	China		Octylphenol	(47.43)			(2018b)
	Bahe River,	River water Nonylphenol	108.1-634.8	10	100%	Wang et al.
	China			(252.57)			(2018b)
	Three	River water Nonylphenol	<1.7-33.3	14	71.4%	Wang et al.
	Gorges			(10.8)			(2016c)
	Reservoir
	Region,
	China
	Three	River water Octylphenol	<0.3-120	14	71.4%	Wang et al.
	Gorges			(32.3)			(2016c)
	Reservoir
	Region,
	China
	Three	River	Nonylphenol	<1.5-8.5	14	85.7%	Wang et al.
	Gorges	sediment		(5.0)			(2016c)
	Reservoir
	Region,
	China
	Three	River	Octylphenol	<0.5-12.4	14	92.9%	Wang et al.
	Gorges	sediment		(5.30)			(2016c)
	Reservoir
	Region,
	China
	Xiangjiang	River water 4-tert-	<0.27-156.1	160	72.2%	Luo et al.
	River, China		Octylphenol	(16.28)			(2019)
	Xiangjiang	River water 4-Octylphenol	<0.67-40.8	160	69.5%	Luo et al.
	River, China			(7.3)			(2019)
	Xiangjiang	River water 4-Nonylphenol	<0.79-12.9	160	74%	Luo et al.
	River, China			(2.65)			(2019)
	Zunyi,	River water Nonylphenol	174-3411	6	100%	Yu et al.
	Guizhou			(1730)			(2017)
	province,
	China
	Pearl River	River water 4-Nonylphenol	27.20-824.18	31	100%	Xie et al.
	networks,			(219.33)			(2020)
	China
							(continued)

Table 1 .

 1

	2 (continued)
	Region,			Concentration	Sample	Detection
	Country	Matrix	Compound	range (mean)	number	frequency References
	Po River	Lake	4-Octylphenol	0.13-1.43	6	100%	Casatta
	delta, Italy	sediment		(0.68)			et al.
							(2016)
	Po River	Lake	Nonylphenol	19.44-202.27	6	100%	Casatta
	delta, Italy	sediment		(82.19)			et al.
							(2016)
	Po River	Lake	4-Nonylphenol	<0.12-1.24	6	50%	Casatta
	delta, Italy	sediment		(0.62)			et al.
							(2016)
	Nationwide,	Recreational	4-Nonylphenol	0.83-12.61	10	83%	Vargas-
	Mexico	water		(3.61)			Berrones
							et al.
							(2020a)
	Cuautla	Surface	4-Nonylphenol	1.23-44.77	9	44%	Calderon-
	River,	water		(7.53)			Moreno
	Mexico						et al.
							(2019)
	Cuautla	Surface	4-tert-	0.30-28.10	9	100%	Calderon-
	River,	water	Octylphenol	(11.24)			Moreno
	Mexico						et al.
							(2019)
	São Paulo	Surface	4-n-Nonylphenol 1-2018 (429) 205	2%	Montagner
	State, Brazil	water					et al.
							(2019)
	São Paulo	Surface	4-n-Octylphenol 2-1029 (266) 205	2%	Montagner
	State, Brazil	water					et al.
							(2019)
	Santos Bay,	Marine	4-Nonylphenol	<10-72.5
	Brazil	sediment		(32.2)

Table 1 . 3

 13 Rare earth element (REE) concentrations (in μg/g) in different environmental compartments in comparison to the average concentrations of the

				UCC f	31	63	7.1	27	4.7	1.0	4.0	0.7	3.9	0.83	2.3	0.30	1.96	0.31	14.0	21
	Maximum	permissible	concentrations	(ng/mL)	10.1	22.1	9.1	1.8	8.2	-	7.1	-	9.3	-	-	-	-	-	-	6.4
	Background	concentrations in	ground water e	(ng/mL)	<0.08	0.956	0.125	<0.39	<0.56	<0.17	0.198	<0.10	0.069	<0.09	0.072	0.175	<0.13	<0.05	0.001	0.416
	Background	concentrations in	surface water 5	(ng/mL)	<0.08	<0.13	<0.08	<0.39	<0.56	<0.17	<0.33	<0.10	<0.22	<0.09	<0.14	<0.07	<0.13	<0.05	<2.80	<0.22
	Runoff water	from traffic	area d , Beijing,	China (ng/mL)	5.56	10.4	1.40	4.04	0.97	0.25	0.91	0.12	0.57	0.13	0.011	0.07	0.43	0.10	-	3.12
		Fertilizer	enriched	with REE c	15,400	24,100	11,800	1100	2000	200	1100	25.8	91.6	4.3	26.9	1.4	5.3	0.5	-	-
	Plant species b -Dicranopteris	dichotoma		Leaves Shoot Root	1568.00 59.39 1305.07	2290.33 738.63 1482.60	149.77 48.53 566.70	1499.00 112.23 687.40	---	29.32 12.53 161.55	75.08 47.49 157.63	85.37 45.85 98.40	47.78 17.11 166.30	13.24 6.39 59.39	13.24 6.56 34.58	8.37 13.50 17.57	18.49 15.45 151.56	7.48 6.18 16.10	33.16 33.40 177.83	219.07 57.70 111.65
	upper continental crust	Soils of	Rare earth ex-mining	element area a	La 94.69	Ce 420.5	Pr 33.79	Nd 112.3	Sm -	Eu 59.84	Gd 42.26	Tb 42.26	Dy 18.66	Ho 12.12	Er 43.5	Tm 10.15	Yb 38.23	Lu 9.33	Sc 39.89	Y 79.2

a Soils of ex-mining area (representative)

[START_REF] Khan | Accumulation, uptake and bioavailability of rare earth elements (REESs) in soil grown plants from exmining area in Perak, Malaysia[END_REF]

b Plant species, Dicranopteris dichotoma

[START_REF] Khan | Accumulation, uptake and bioavailability of rare earth elements (REESs) in soil grown plants from exmining area in Perak, Malaysia[END_REF]

c Fertilizer enriched with rare earth elements

[START_REF] Hu | Rare earth elements in soils[END_REF]

d Runoff water from traffic area, Beijing, China

[START_REF] Shajib | Rare earth elements in surface specific urban runoff in Northern Beijing[END_REF]

e Background concentrations in surface/ground water and maximum permissible concentrations

[START_REF] Sneller | Maximum permissible concentrations and negligible concentrations for rare earth elements (REES)[END_REF]

f UCC -recommended average concentrations of rare earth elements in the upper continental crust

[START_REF] Rudnick | Composition of the continental crust[END_REF]

Table 1 .4

 1 Overview of the measured engineered nanoparticle concentrations in surface waters (SP-ICP-MS single particle inductively coupled plasma mass spectrometry, ICP-OES inductively coupled plasma optical emission spectroscopy, ET-AAS electrothermal atomic absorption spectrometry)

			Analytical
	Material	Location	technique	Results	References
	Titanium	Clear	SP-ICP-MS	5 to 28 μgTi/L; metals	Reed et al.
	dioxide	Creek,		naturally co-occurring with	(2017)
		Colorado		Ti (Al, Fe) also showed an
		collected		increase during bathing
		hourly over		periods, suggesting the Ti
		a 72 h		increase may be partially of
		period		sediment resuspension
	Silver	Dutch rivers SP-ICP-MS56-60 Silver nanoparticles (average	Peters et al.
				size 15 nm) at 0.3-2.5 ng/L	(2018)
	Cerium oxide	Dutch rivers SP-ICP-MS56-60 Cerium oxide nanoparticles	Peters et al.
				(average size 19 nm) at	(2018)
				0.4-5.2 ng/L
	Titanium	Dutch rivers SP-ICP-MS56-60 Titanium dioxide particles	Peters et al.
	dioxide			(300 nm) at 0.2-8.1μg/L	(2018)
	Titane total	North East	SP-ICP-MS	3.7-11.2 μgTi/L	Piccoli
		Italy			et al. (2018)
	Cerium total	North East	SP-ICP-MS	0.2-0.4 μgCe/L	Piccoli
		Italy			et al. (2018)
	Zinc total	North East	SP-ICP-MS	0.12-7.9 μgZn/L	Piccoli
		Italy			et al. (2018)
	Silver total	North East	SP-ICP-MS	0.64-0.80 μgAg/L	Piccoli
		Italy			et al. (2018)
	Silver	Melana	ICP-OES	0.13 ± 0.06 to	Syafiuddin
		River,		10.16 ± 1.32 mg/L	et al. (2018)
		Malaysia
	Silver	Sekudai	ICP-OES	0.10 ± 0.00 to	Syafiuddin
		River,		9.63 ± 0.80 mg/L	et al. (2018)
		Malaysia
	Titanium	Salt River,	SP-ICP-MS	Maximum concentration of	Venkatesan
	dioxide	Arizona		659 ng/L	et al. (2018)
	Silver-b-	River Isar,	ET-AAS after	1-2 ng/L; load peak of	Wimmer
	nanoparticles	southern	cloud point	20.88 ng/L near the	et al. (2019)
	(silver-based	Germany	extraction	wastewater treatment plant
	nanoparticles)			Decrease in silver-b-NP
				concentration at 1.5 km
				downstream of discharge
				wastewater treatment plant
				points
	Ti	Lake Taihu,	SP-ICP-MS	0.09 to 10.2μg/L, in October	Wu et al.
		China		2016	(2020a)
				0.11 to 4.16μg/L, in April
				2018

Table 1 .

 1

	5 (continued)
				Concentration
	Country	Water type	Emerging substance	(ng/L)	References
	Brazil (São	Drinking water Caffeine	4083	Peña-Guzmán et al.
	Roque)				(2019)
	Brazil (São	Drinking water Caffeine	121	Montagner et al.
	Paulo)				(2019)
	Brazil (Rio	Drinking water	Caffeine	18,828	Machado et al. (2016)
	Grande)	supply reservoir
	Brazil (São	Surface water	Bisphenol A	2-13,016	Montagner et al.
	Paulo)				(2019)
	Brazil (Rio	Drinking water	Bisphenol A	11	Machado et al. (2016)
	Grande)	supply reservoir
	Brazil (São	Drinking water Bisphenol A	23	Montagner et al.
	Paulo)				(2019)
	Brazil (São	Drinking water Bisphenol A	0.5	Peña-Guzmán et al.
	Roque)				(2019)
	Brazil (São	Surface water	Cocaine	10	Montagner et al.
	Paulo)				(2019)
	Brazil (São	Surface water	Benzoylecgonine	133	Montagner et al.
	Paulo)				(2019)
	Colombia	Wastewater	Benzoylecgonine	4000	Bijlsma et al. (2016)
	(Bogotá)
	Colombia	Wastewater	Amphetamines	12-68	Bijlsma et al. (2016)
	(Bogotá)
	Brazil (São	Drinking water Triclosan	2-37	Montagner et al.
	Paulo)				(2019)
	Brazil (Rio	Surface water	Atrazine	5-49	Caldas et al. (2019)
	Grande)
	Brazil (São	Drinking water Atrazine	687	Montagner et al.
	Paulo)				(2019)
	Brazil (Rio	Drinking water Atrazine	5-37	Caldas et al. (2019)
	Grande)
	Brazil	Drinking water Atrazine	2-6000	Machado et al. (2016)
	Mexico	Groundwater	Endrin	3.2 mg/L	Polanco-Rodríguez
	(Yucatan)				et al. (2018)
	Mexico	Groundwater	γ-Lindane	10.86 mg/L	Polanco-Rodríguez
	(Yucatan)				et al. (2018)
	Mexico	Groundwater	Heptachlore	12.54 mg/L	Polanco-Rodríguez
	(Yucatan)				et al. (2018)

  1,141,748 km 2 , a large marine area covering 928,660 km 2 and a population of46,581,823 (Departamento Administrativo Nacional, DANE 2011). Colombia is a privileged country because of its geographical position in the continent, which gives it direct access to both ocean Atlantic and Pacific. Colombia has many water sources throughout its territory and the most important biodiversity not only in the region but also in the World. The country has indeed many rivers, the most important of which are the following: Amazon (6992.6 km, shared with Peru and Brazil), Caquetá (Japura, 2816.3 km, shared with Brazil), Negro (2230.5 km, shared with Brazil and Venezuela), Orinoco (2140.4 km, shared with Venezuela), Putumayo (1609.3 km, shared with Peru and Brazil), Guaviare (1496.6 km, shared with Venezuela), Arauca (1049.2 km, shared with Venezuela), Cauca (965.6 km), Goal (804.6 km, shared with Venezuela), Magdalena (528.8 km) and its affluent Rio Bogotá. Concerning the latter river, it originates in the northeastern region of Cundinamarca, in the lagoon valley of Paramo Guacheneque, municipality of Villa Pinzon, Eastern Cordillera of Colombia, at 3300 m above sea level. The waters of the Bogotá River flow for 380 kilometers to Girardot, where they flow into the Magdalena River. Its basin is located in the center of the country, in the department of Cundinamarca, with an area of approximately 6.000 km 2[START_REF] Hernández | LC-QTOF MS screening of more than 1,000 licit and illicit drugs and their metabolites in wastewater and surface waters from the area of Bogotá, Colombia Bioanal[END_REF] Bedoya-Ríos et al. 2018; Bedoya-Ríos and Lara-Borrero 2018).

100%[START_REF] Santos | Multiresidue determination and predicted risk assessment of contaminants of emerging concern in marine sediments from the vicinities of submarine sewage outfalls[END_REF]

(continued)

Acknowledgements

Nadia Morin-Crini and Grégorio Crini (Besançon, France) thanks the FEDER (Fonds Européen de Développment Régional) for its financial support (NIRHOFEX Program) and the Région Bourgogne Franche-Comté (France) for the research grant awarded to Guest Research Director G. Torri. Ana Rita Lado Ribeiro (Porto, Portugal) acknowledges the support from Projects: PTDC/QUI-QAN/30521/2017 -POCI-01-0145-FEDER-030521 -funded by FEDER funds through COMPETE2020 -Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES and Base Funding -UIDB/50020/2020 of the Associate Laboratory LSRE-LCM -funded by national funds through FCT/MCTES (PIDDAC).