Nicolas Layglon
email: nicolas.layglon@unige.ch

Véronique Lenoble

Longo Louis

Stéphane Sébastien D'onofrio

Jean-Ulrich Mounier

Davide Mullot

Dario Sartori

Cédric Omanović

Benjamin Garnier

Misson

Sébastien

D ' Onofrio

Stéphane Mounier

Jean-Ulrich Mullot

Davide Sartori

Dario Omanović

Cédric Garnier

Benjamin Misson

Sébastien D ' Onofrio

Cd transfers during marine sediment resuspension over short and long-term period: Associated risk for coastal water quality

Keywords: cadmium, remobilization, sediment resuspension, water quality, Environmental 33 Quality cadmium, remobilization, sediment resuspension, water quality, Environmental 32 Quality Standards (EQS) 33 Methodology, Investigation, Validation, Formal analysis, Data interpretation and curation, Visualization, Writingoriginal draft, Writing -Review Methodology, Investigation, Validation, Data Curation, Writing - Conceptualization, Investigation, Formal analysis, Review & Editing Conceptualization, Investigation, Formal analysis, Review Methodology, Investigation, Validation, Data Curation, Writing -Review Conceptualization, Methodology, Funding acquisition Conceptualization, Methodology, Investigation, Validation, Formal analysis, Data interpretation, Writing -Review & Editing, Supervision, Project coordination, Funding acquisition

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I Introduction 35

Coastal areas are of great interest for humankind, due to the huge amount of resources 36 therein, leading to an increase in population along the coastlines. While the population 37 increased, sanitary infrastructure did not, causing an increase of contaminants release towards Hanau, Germany) for at least 24 h in order to completely decompose organic matter. Samples 86 were then stored at ambient temperature until dissolved Cd analysis. The remaining 87 unprocessed water was kept at ambient temperature and day light until further resuspension 88 experiments. 89

One sediment core was sampled at each site using an interface corer (Uwitec) equipped 90 with PVC tubes of 90 mm in diameter. The first 30 cm of the core were sliced and homogenized 91 under inert N2 atmosphere. We are aware that diagenetic processes could have leaded to 92 different physical-chemical properties of the sediment within such a thick sediment slice, 93 however, it represents well the sediment thickness targeted by sediment management 94 operations in harbor areas. An aliquot of each homogenized sediment sample was submitted 95 to centrifugation (4248 RCF (Relative Centrifugal Force), 20 °C for 15 min Sigma 3-18K) to 96 separate porewater from sediment. After removing the supernatant, the pellet was weighed 97 before and after freeze-drying in order to determine the water content of each sediment. 98 Lyophilized sediments were finally sieved under 2 mm and crushed in a Planetary Ball Mill 99 PM 100 (Retch). Aqua-regia digestion was performed on the lyophilized sediments using a 100 microwave digestion (Milestone) prior to assess the Cd concentration on particles. This 101 protocol was previously described (Cukrov et al., 2019;Tessier et al., 2011) and validated 102 using a certified material n = 20,accuracy 103 between 0.9 and 7% according to the considered element; Tessier et al., 2011). In order to 104 determine the easily exchangeable fraction of Cd, an acid extraction (1 M HCl) was performed 105 (Larrose et al., 2010). The extraction was achieved by mixing 100 mg of freeze-dried 106 homogenous sediment with 10 mL of 1 M HCl (Merck, suprapur solution) in a polypropylene 107 tube shaken head-over-head (6 rpm, Heidolph Reax 20) for 24 h. After centrifugation (4,248 108 RCF, 15 min), the supernatant was filtered through 0.2 μm syringe filters and stored in the 109 dark at 4 °C. Remaining homogenized and wet sediments were kept anoxic at ambient 110 temperature until further resuspension experiment. 111

II.2 Laboratory resuspension experiments 112

In order to evaluate the kinetics of Cd remobilization during sediment resuspension, 113 laboratory experiments were launched within 48 h after sampling, using pre-cleaned 5L PTFE 114 bottles. The sediment was kept under an inter atmosphere (N2) to prevent sediment oxidation. 115

Experiments were carried out with the same sediment:water ratio for all three sampling 116 locations. Since the sediment collected in the different sites have different water content, the 117 amount of sediment particles added were different, despite an identical mass of wet sediment 118 (Table 1). Two different kind of resuspension experiments were performed. The first series of 119 experiment was carried out to study the kinetics of Cd transfers between sediment and 120 seawater. It was conducted with a sediment:water ratio of 2.5 g of wet sediment per liter of 121 seawater (representing approximately 1 g of dry sediment per liter of seawater) in 5L PTFE 122 bottle, submitted to continuous head-over-head shaking (15 rpm,Heidolph Reax 20). This ratio 123 was frequently used in previous studies ( Dang et al., 2020;Guigue et al., 2017;Millward 124 and Liu, 2003;Moran and Moore, 1991) and represents a resuspension event related to 125 nautical traffic. Water-sediment mixture was sub-sampled (180 mL) at exponentially 126 increasing intervals to allow the coverage of both short and long-term Cd transfer processes: 127 5, 15, 30 min, 1, 3, 7 h, 1, 2, days, 1 and 2 weeks. The second series of experiment was performed 128 to quantify the impact of the quantity of resuspended sediment onto Cd transfers. Sediment 129 and seawater were mixed in 500 mL FEP bottles during 2 weeks with 10 different 130 sediment:water ratios (0. 05, 0.125, 0.25, 0.5, 1.25, 2.5, 5, 12.5, 25, 125 g of wet sediment per liter 131 of seawater representing approximately 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 50 g of dry sediment 132 per liter of seawater, respectively (Table 1). These ratios allowed to represent a large diversity 133 of resuspension processes, from natural wind events in shallow coastal areas (<0.5 gL -1 , (Jiang 134 et al., 2020)) to dredging operations (~10-50 gL -1 , (Nichols et al., 1990)). The water-sediment 135 mixture was only sampled after two weeks of mixing. For both experiments, samples were 136 filtered, treated and stored as described above for seawater prior to dissolved Cd 137 concentration measurement. 138

In parallel of the first series of experiments performed with a sediment:water ratio of 139 2.5 gL -1 , pH, Eh and O2 were measured at each interval sampling time and every day until the 140 end of the experiment in a separate 1 L HDPE bottle (with the same conditions and sediment 141 load) to avoid potential contamination by the probes. The pH measurement was carried out 142 with a combined electrode (Ag|AgCl|KCl 3 M) of the microtip type (diameter of 5 mm, 143 Bioblock Scientific). The latter has been calibrated beforehand (before each new set of 144 measurement) using buffer solution at pH 4.01, 7.01 and 10.01 (HANNA). Redox electrode was 145 made of Pt (Radiometer Copenhagen) coupled to the reference electrode in Hg|Hg2Cl2|KCl 3 146 M (Radiometer Analytical, Eref = 255 mV/NHE, 25°C), calibrated with the Zobell's solution (Eh 147 = 430 mV/NHE at 25°C, Thermo Scientific). 148

Each experiment was performed in one replicate, therefore the standard deviation 149 calculated for the total dissolved Cd concentrations represents the measurements variability. 150 National Research Council of Canada) for the validation of the aqua-regia digestion. The 156 measured Cd concentration was PACS-2 was 2.11 ± 0.14 mgkg -1 (n=5) while the certified values 157 is 2.11 ± 0.15 mgkg -1 . The French authorities (JORF n°184 10-08-2000) have defined N1 (1.2 158 µgCdg -1 ) and N2 (2.4 µgCdg -1 ) levels to evaluate the potential impact of sediment onto the 159 environment. Below N1 level, the potential impact of the sediment is considered neutral or 160 negligible, meaning that the management of the sediment does not therefore require any 161 particular precaution. Between N1 and N2, further investigation may be necessary; the 162 assessments of the overall toxicity of the sediments should be performed. Above N2 Level, an 163 impact on the environment is expected, and the dredged sediment is considered as a 164 hazardous waste which must be stored in appropriate dump. The Italian Ministerial Decree 165

173/2016 has defined L1 (the lowest chemical level of reference) and L2 (the highest chemical 166 level of reference) levels which, together with the outcome of toxicological tests (weight of 167 evidence criteria), contributes to the classification and identification of appropriate 168 management for marine and brackish sediments to be dredged. Below L1 level (0.3 µgCdg -1 ), 169 with low or no adverse results from ecotoxicological tests, sediment can be dredged and used 170 for beach nourishment, dumped in offshore marine areas (over 3mn), or transported and 171 disposed of in a manner that minimizes the release of contaminants either into solution or by 172 resuspension. Between L1 and L2 levels (0.3 -0.8 µgCdg -1 ) with low or no adverse outcome 173 from bioassays, sediment can be dumped in off-shores marine areas (over 3 m) or addressed 174 in confined disposal facilities (CDF) effectively isolated from the environment. An 175 environmental monitoring plan must be foreseen for each option listed above. Finally, above 176 the L2 levels, sediment must be dredged and transported with care, and effectively isolated 177 from the environment upon final disposal. 178

To determine the organic carbon content, the crushed sediment was acidified with 179 (Fisher Scientific, Analytical Reagent grade, 85%) to eliminate inorganic carbon. Then, the 180 samples were measured on a CHNS flash 2000 (Thermo Electron) following the method 181 described by Benner and Strom (1993). The total sulfur content was measured after mixing 182 around 3 mg of freeze-dried sediments with approximately 1.5 mg of vanadium pentoxide 183 V2O5 (Thermo Fisher Scientific). For both carbon and sulfur measurements, two reference soils 184 were used, NC and NCS (Thermo Fisher Scientific). Each sample was analyzed in triplicate. 185

The particle size distribution was determined using a laser diffraction particle-size 186 analyzer LS 13320 (Beckman Coulter Inc.). Wet sediment samples were dispersed in deionized 187 Automated measurements were controlled by the GPES 4.9 software (EcoChemie). 195 Quantification of the metals concentrations was performed using the standard addition 196 method, automated using syringe burettes (Pump XE 1000, TECAN). Voltammograms were 197 processed (peak height of 2 nd derivative as analytical signal characteristic) using ECDSOFT 198 software (Cobelo-García et al., 2014;Omanović and Branica, 1998). The percentage of Cd 199 desorption from sediment was calculated by subtracting the Cd quantity in the initial seawater 200 from the Cd quantity measured at the end of the experiment and divided by the quantity of 201 Cd added in the mixing solution by sediment particles. 202

III

Results and discussion 203

III.1 Sediment and seawater initial characteristics 204

The salinity of seawater was 37.9 for La Spezia, 37.6 for Olbia and 38.2 for Toulon, while 205 the pH values of overlying water for these three sites were 8. 32, 7.55 and 7.87, respectively. 206 The percentage of oxygen saturation of the overlying water was 89, 101 and 90.3 %. The initial 207 pH values of the seawater used for the resuspension experiments were 8.30, 8.36 and 7.79 for 208 La Spezia, Olbia and Toulon respectively. The initial dissolved Cd concentrations in seawater 209 were 15.74, 7.87 and 11.24 ngL -1 for La Spezia, Olbia and Toulon respectively, which is 210 consistent with the literature for these bays or their coastal surroundings (Breder, 1987;Coclet 211 et al., 2019). The dissolved Cd concentrations in the three harbors were below the admissible 212 dissolved cadmium concentration in seawater (more than 200 mgL -1 CaCO3) defined by the 213 EQS (2008/105/EC). 214

The sediment from La Spezia was equally composed of clay and sand (44 and 46 %) 215 while the silt fraction represented only 10 %. The sediment from La Olbia and Toulon were 216 mainly composed of clay (65 and 52 % respectively) while the sand fraction represented 28 217 and 40 % respectively. Finally, the silt fraction was the lowest one with only 7 and 8 % in the 218 sediment from Olbia and Toulon. 219 Cadmium contents were 0.10, 0.20 and 0.37 µgg -1 in the sediment of La Spezia, Olbia 220 and Toulon respectively. Contents observed in Toulon and Olbia sediments are consistent with 221 the literature for these bays (Schintu et al., 1991;Tessier et al., 2011) while the content 222 observed in La Spezia sediment were lower than that previously observed (Breder, 1987). The 223 easily-exchangeable proportion of Cd in the three sediments were 63,47 and 38% for La Spezia,224 Olbia and Toulon respectively. Such range of easily exchangeable Cd proportion was already 225 observed in the literature (Dang et al., 2015a;El Houssainy et al., 2020). 226 The percentage of organic carbon in the sediment was 0.42, 2.12 and 2.39 % for La 227 Spezia, Olbia and Toulon respectively. The percentage of total sulfur was 0.35, 0.91 % and 228 0.27 % in La Spezia, Olbia and Toulon respectively. 229

Given that the sediments were sampled in France and Italy, we compared their Cd 230 contents to national laws framing marine sediment management. Sediment from Toulon 231 presented Cd content lower than the regulatory N1 level defined by the French authorities 232 (JORF n°184 10-08-2000). As a consequence, its potential impact regarding Cd is considered 233 neutral or negligible and the management of the sediment does not require any particular 234 precaution. The Cd content in La Spezia and Olbia were below the Italian lower chemical 235 exceedance Level and could thus be dredged, transported and disposed if the release of 236 contaminants into solution or by resuspension is minimized (Italian Ministerial Decree 237 173/2016). 238

III.2 Quantity and partitioning of Cd from resuspended sediments in the different 239 experiments 240

The amount of total particulate and easily-exchangeable Cd added in each experiment 241 are given in Table 2. The input of particulate Cd was 1.6-2.8 times higher in Toulon 242 experiments compared to that of Olbia and La Spezia and the exchangeable fraction was 1.3-243 1.7 times higher in Toulon experiments compared to that of Olbia and La Spezia. 244

Table 2 : Amount of total particulate and easily-exchangeable Cd expressed in ng added in each 245 performed experiment 246

III.3 Variations of physical-chemical parameters over time 247

The percentage of dissolved oxygen remained above 100% all along the experiments 248 for both Olbia and Toulon. Unfortunately, the dissolved oxygen couldn't be measured in La 249 Spezia experiment due to a sensor failure. The redox potential (Eh) started 359, 322 and 291 250 mV in La Spezia, Olbia and Toulon experiments respectively. During the very first three hours 251

Eh dropped down to 125, 53.7 and 170 mV in La Spezia, Olbia and Toulon experiments 252 respectively. Then, Eh started to slightly increase but stayed below the initial seawater values 253 for La Spezia and Toulon experiments, while it reached back the initial seawater value in Olbia 254 experiment. The percentage of dissolved Cd species is greatly influenced by the pH value of 255 seawater (Andreas and Zhang, 2014). Thus, the variations of pH value over time were 256 observed with a 2.5 gL -1 sediment:water ratio. The pH value in La Spezia experiment dropped 257 from 8.30 down to 7.87 the first minutes right after the addition of sediment (Figure 1), while 258 no similar early sharp decrease was observed for Olbia and Toulon (Figure 1). From 5 th 259 minutes of mixing to the end of the experiment, a similar temporal variation of pH was 260 observed for La Spezia and Olbia experiments (Figure 1, Spearman's correlation test, ρ = 0.936, 261 p < 0.05). Between 48 h and the end of the experiments, the pH value dropped down to 7.40 262 and 7.73 for La Spezia and Olbia, respectively. pH decrease during sediment resuspension has 263 already been observed (Cabrol et al., 2017;Dang et al., 2015b;Pía Di Nanno et al., 2007;264 Zouch et al., 2018) and could suggested a relatively common process governing pH, 265 irrespective of the sediment composition. We have already demonstrated (Layglon et al., 266 2021) that the pH decrease during sediment resuspension (performed with 50 times higher 267 sediment content) could be abiotically controlled and therefore might result from the increase 268 in dissolved acidic substances. Richards et al., (2018) suggested that the oxidation of acid 269 volatile sulfide (AVS) during the resuspension of anoxic sediment could induce an increasing 270 concentration of dissolved acidic substances. Surprisingly, in the experiment with samples 271 from Toulon, while pH values showed a similar decreasing trend until 8 days of mixing 272 (Spearman's correlation test, ρ = 0.850, ρ = 0.899 respectively for Toulon-La Spezia and Toulon-273 Olbia, p < 0.05), pH increased from 8 days to the end of the experiment and reached values 274 similar to initial one (Figure 1). This observation remains unexplained for the moment.

III.4 Kinetics of Cadmium transfers 283

First, Cd experienced a strong and fast removal from the dissolved phase, observed 284 within a few minutes (Figure 2A) for all experiments. As a consequence, dissolved 285 concentrations were decreased by a factor 15.3, 10.8 and 8.4 for La Spezia, Toulon and Olbia, 286 respectively (Figure 1B). Cd is known to have a strong affinity for carbonates and clays 287 (Pickering, 1983;Shirvani et al., 2006;Superville et al., 2015;Zheng et al., 2007), as well as 288 with OM (Tahervand and Jalali, 2016), therefore its removal might be attributed to its 289 adsorption onto resuspended carbonates, OM and/or clays. Dissolved Cd concentrations then 290 Cd remobilization was already explained in the literature, and is related to the competition of 294 major seawater cations with trace metals for specific adsorption sites and the formation of 295 metal chloro-complexes (Calmano et al., 1993;Prause et al., 1985;Tahervand and Jalali, 296 2016;Zhuang et al., 1994). 297

At the end of the experiments, the maximal dissolved Cd concentrations were 90.0, 60.8 298 and 240.6 ngL -1 for La Spezia, Olbia and Toulon experiments, respectively (Figure 2A), 299 representing a huge increase in concentration compared to the initial seawater concentrations 300

(5.8-fold, 8.1-fold and 22.1-fold higher in La Spezia, Olbia and Toulon, respectively). When 301 focusing on the absolute Cd concentration (Figure 2A), during the desorption step, the 302 maximal increase in dissolved Cd was higher in Toulon (229 ngL -1 ) than in La Spezia (74 ngL - 303 1 ) and the lowest value was found for Olbia (53 ngL -1 ). As seen above, the input of particulate 304 Cd was 1.6 and 2.8 times higher in Toulon experiments compared to that of La Spezia and 305 Olbia, respectively. The percentage of desorbed Cd was similar in La Spezia and Toulon 306 experiments (47 and 51% respectively) and was found to be smaller in Olbia experiment (20%). 307

The difference in the percentage of desorbed Cd did neither correspond to differences in Cd 308 total content between the three sediments, nor to their differences in easily-exchangeable 309 fraction of Cd. Therefore, none of total Cd content and Cd easily-extractable fraction appeared 310 as the main parameter leading to Cd remobilization when, however, they are the most 311 commonly measured parameters and those used for the management of sediments. The more 312 alkaline pH measured in the experiment carried out with Olbia sediment (8.1 ± 0.20 compared 313 to 7.70 ± 0.08 and 7.63 ± 0.16 for La Spezia and Toulon, respectively) could explain the lowest 314 Cd release into seawater (Figure 1: Figure 1) (Andreas and Zhang, 2014). While the kinetics 315 of Cd remobilization were similar in the three experiments, the amplitude of Cd 316 adsorption/desorption were dependent on the mixing (Figure 2). 317 318 sediment:water ratio). Panel A represents its absolute variation while Panel B represents its relative 320 variation. As a consequence, a value above the black dotted line will correspond to an increase compared 321

to Cd in initial seawater, whereas a value below this line will correspond to a decrease. Note that the x 322 and y axis are on log scale. The dissolved Cd concentration indicated at x = 0.01 in panel A represents 323

Cd concentration of the initial seawater before the addition of sediment. 324

III.5 Effects of the quantity of resuspended particles onto cadmium transfers 325

Using a ratio of 2.5 gL -1 , we showed that the kinetics of Cd remobilization was similar 326 with different initial samples, and that the maximal dissolved Cd concentrations was observed 327 after 2 weeks of mixing. Therefore, we evaluated the impact of sediment resuspension 328 intensity after 2 weeks of mixing by varying the sediment:water ratio. The increase of 329

B

suspended particulate matter led to an increase in final dissolved Cd concentrations in the 330 three experiments (Figure 3). However, the increase in dissolved Cd concentration was not 331 linearly linked to the increase of suspended particulate matter and thus of the quantity of total 332 or easily extractable Cd (Figure 3), pointing out a threshold effect that remains to be explained. 333

The dissolved Cd concentrations obtained with a ratio of 2.5 gL -1 are consistent with the one 334 observed in the previous kinetics experiments (Figure 2 and Figure 3). For the highest S/L 335 ratio (i.e. 125 gL -1 ), representative of a suspended particulate matter concentration in seawater 336 during dredging operations (Nichols et al., 1990), dissolved Cd increased up to 615, 2050 and 337 3624 ngL -1 in Olbia, La Spezia and Toulon experiments, respectively, corresponding to a 82-338 fold, 132-fold and 330-fold increase when compared to the initial concentration in seawater 339 (Figure 3). Therefore, the maximal concentration accepted by the EQS (2008/105/EC) 340 (1500 ngL -1 in water containing more that 200 mgL -1 CaCO3) was exceeded for experiments of 341 La Spezia (by a factor 1.4) and Toulon (by a factor 2.4) experiments. These experiments showed 342 that the EQS were punctually overpassed even if the Cd contents were lower than the N1 and 343 L1 levels for La Spezia, and below the N1 and L2 levels for Toulon sediments. therein, leading to an increase in population along the coastlines. While the population 36 increased, sanitary infrastructure did not, causing an increase of contaminants release towards 37 the environment occurs, threatening the ecosystems, the marine species, and the human 38 population health. To protect the marine environment, the European Union defined 39 environmental regulations concerning both seawater and sediments. Concerning the 40 concentration of chemical substances in the water, the European Union Water Framework 41 Directive (WFD-2008/105/ EC) has defined environmental quality standards (EQS) thresholds 42 that must not be exceeded to limit human impact on natural ecosystems. EU member states 43 consider sediment contamination for the management of sediments in harbor areas through 44 very heterogeneous standards, mainly in order to limit the resuspension of chemically 45 contaminated particles. Sediments indeed accumulate a high amount of toxic substances (El 46

Houssainy et al., 2020; Guigue et al., 2017; Misson et al., 2016; Schintu et al., 2016, 1991). 47

Both natural and human-induced sediment resuspension often occur in coastal areas and, 48 during resuspension, chemical substances can easily be remobilized through the dissolved 49 phase towards the water column (Ciffroy et al., 2019;Dang et al., 2020;de Freitas et al., 50 2019). The remobilization of chemical substances from sediment can therefore potentially alter 51 water quality with regard to the EU-WFD. 52 Among this chemical substances, cadmium (Cd) is a non-essential, harmful trace metal, 53 which causes serious problems due to its severe toxicity towards organisms (Miao and Wang, 54 2006; Satarug et al., 2003). Cadmium remobilization occurs due to the competition of major 55 seawater cations with trace metals for specific adsorption sites and the formation of metal 56 chloro-complexes (Calmano et al., 1993;Prause et al., 1985;Tahervand and Jalali, 2016;57 Zhuang et al., 1994). The kinetics of transfer found in the previous literature was only 58 evaluated after 12h, a time which seems long in view of the process highlighted after a few minutes for other elements (Dang et al., 2020). In this context, the first aim of this study was 60 to study and compare the succession and amplitude of Cd transfers between the dissolved and 61 particulate phases from minutes to weeks. For that, dissolved Cd concentration was measured 62 over time during resuspension at a fixed sediment:water ratio of sediments sampled in 63 different Mediterranean urbanized bays. Then, on the basis of the observed kinetics, the 64 influence of the quantity of resuspended sediment on Cd release into the dissolved phase was 65 assessed at week scale through a second experiment using different sediment:water ratios, 66 representative of low (wind induced resuspension), medium (nautical activities) and high 67 Hanau, Germany) for at least 24 h in order to completely decompose organic matter. Samples 85 were then stored at ambient temperature until dissolved Cd analysis. The remaining 86 unprocessed water was kept at ambient temperature and day light until further resuspension 87 experiments. 88

One sediment core was sampled at each site using an interface corer (Uwitec) equipped 89 with PVC tubes of 90 mm in diameter. The first 30 cm of the core were sliced and homogenized 90 under inert N2 atmosphere. We are aware that diagenetic processes could have leaded to 91 different physical-chemical properties of the sediment within such a thick sediment slice, 92 however, it represents well the sediment thickness targeted by sediment management 93 operations in harbor areas. An aliquot of each homogenized sediment sample was submitted 94 to centrifugation (4248 RCF (Relative Centrifugal Force), 20 °C for 15 min Sigma 3-18K) to 95 separate porewater from sediment. After removing the supernatant, the pellet was weighed 96 before and after freeze-drying in order to determine the water content of each sediment. 97 Lyophilized sediments were finally sieved under 2 mm and crushed in a Planetary Ball Mill 98 PM 100 (Retch). Aqua-regia digestion was performed on the lyophilized sediments using a 99 microwave digestion (Milestone) prior to assess the Cd concentration on particles. This 100 protocol was previously described (Cukrov et al., 2019;Tessier et al., 2011) and validated 101 using a certified material n = 20,accuracy 102 between 0.9 and 7% according to the considered element; Tessier et al., 2011). In order to 103 determine the easily exchangeable fraction of Cd, an acid extraction (1 M HCl) was performed 104 (Larrose et al., 2010). The extraction was achieved by mixing 100 mg of freeze-dried 105 homogenous sediment with 10 mL of 1 M HCl (Merck, suprapur solution) in a polypropylene 106 tube shaken head-over-head (6 rpm, Heidolph Reax 20) for 24 h. After centrifugation (4,248 107 RCF, 15 min), the supernatant was filtered through 0.2 μm syringe filters and stored in the 108 dark at 4 °C. Remaining homogenized and wet sediments were kept anoxic at ambient 109 temperature until further resuspension experiment. 110

II.2 Laboratory resuspension experiments 111

In order to evaluate the kinetics of Cd remobilization during sediment resuspension, 112 laboratory experiments were launched within 48 h after sampling, using pre-cleaned 5L PTFE 113 bottles. The sediment was kept under an inter atmosphere (N2) to prevent sediment oxidation. 114

Experiments were carried out with the same sediment:water ratio for all three sampling 115 locations. Since the sediment collected in the different sites have different water content, the 116 amount of sediment particles added were different, despite an identical mass of wet sediment 117 (Table 1). Two different kind of resuspension experiments were performed. The first series of 118 experiment was carried out to study the kinetics of Cd transfers between sediment and 119 seawater. It was conducted with a sediment:water ratio of 2.5 g of wet sediment per liter of 120 seawater (representing approximately 1 g of dry sediment per liter of seawater) in 5L PTFE 121 bottle, submitted to continuous head-over-head shaking (15 rpm, Heidolph Reax 20). This ratio 122 was frequently used in previous studies ( Dang et al., 2020;Guigue et al., 2017;Millward 123 and Liu, 2003;Moran and Moore, 1991) and represents a resuspension event related to 124 nautical traffic. Water-sediment mixture was sub-sampled (180 mL) at exponentially 125 increasing intervals to allow the coverage of both short and long-term Cd transfer processes: 126 5, 15, 30 min, 1, 3, 7 h, 1, 2, days, 1 and 2 weeks. The second series of experiment was performed 127 to quantify the impact of the quantity of resuspended sediment onto Cd transfers. Sediment 128 and seawater were mixed in 500 mL FEP bottles during 2 weeks with 10 different 129 sediment:water ratios (0.05, 0.125, 0.25, 0.5, 1.25, 2.5, 5, 12.5, 25, 125 g of wet sediment per liter 130 of seawater representing approximately 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 50 g of dry sediment 131 per liter of seawater, respectively (Table 1). These ratios allowed to represent a large diversity 132 of resuspension processes, from natural wind events in shallow coastal areas (<0.5 gL -1 , (Jiang 133 et al., 2020)) to dredging operations (~10-50 gL -1 , (Nichols et al., 1990)). The water-sediment 134 mixture was only sampled after two weeks of mixing. For both experiments, samples were 135 filtered, treated and stored as described above for seawater prior to dissolved Cd 136 concentration measurement. 137

In parallel of the first series of experiments performed with a sediment:water ratio of 138 2.5 gL -1 , pH, Eh and O2 were measured at each interval sampling time and every day until the 139 end of the experiment in a separate 1 L HDPE bottle (with the same conditions and sediment 140 load) to avoid potential contamination by the probes. The pH measurement was carried out 141 with a combined electrode (Ag|AgCl|KCl 3 M) of the microtip type (diameter of 5 mm, 142 Bioblock Scientific). The latter has been calibrated beforehand (before each new set of 143 measurement) using buffer solution at pH 4.01, 7.01 and 10.01 (HANNA). Redox electrode was 144 made of Pt (Radiometer Copenhagen) coupled to the reference electrode in Hg|Hg2Cl2|KCl 3 145 M (Radiometer Analytical, Eref = 255 mV/NHE, 25°C), calibrated with the Zobell's solution (Eh 146 = 430 mV/NHE at 25°C, Thermo Scientific). 147

Each experiment was performed in one replicate, therefore the standard deviation 148 calculated for the total dissolved Cd concentrations represents the measurements variability. 149 The concentration of Cd in sediment after aqua-regia digestion or acid extraction were 153 measured by HR-ICP-MS after 20-fold dilution. A certified material was used (PACS-2, 154 National Research Council of Canada) for the validation of the aqua-regia digestion. The 155 measured Cd concentration was PACS-2 was 2.11 ± 0.14 mgkg -1 (n=5) while the certified values 156 is 2.11 ± 0.15 mgkg -1 . The French authorities (JORF n°184 10-08-2000) have defined N1 (1.2 157 µgCdg -1 ) and N2 (2.4 µgCdg -1 ) levels to evaluate the potential impact of sediment onto the 158 environment. Below N1 level, the potential impact of the sediment is considered neutral or 159 negligible, meaning that the management of the sediment does not therefore require any 160 particular precaution. Between N1 and N2, further investigation may be necessary; the 161 assessments of the overall toxicity of the sediments should be performed. Above N2 Level, an 162 impact on the environment is expected, and the dredged sediment is considered as a 163 hazardous waste which must be stored in appropriate dump. The Italian Ministerial Decree 164

173/2016 has defined L1 (the lowest chemical level of reference) and L2 (the highest chemical 165 level of reference) levels which, together with the outcome of toxicological tests (weight of 166 evidence criteria), contributes to the classification and identification of appropriate 167 management for marine and brackish sediments to be dredged. Below L1 level (0.3 µgCdg -1 ), 168 with low or no adverse results from ecotoxicological tests, sediment can be dredged and used 169 for beach nourishment, dumped in offshore marine areas (over 3mn), or transported and 170 disposed of in a manner that minimizes the release of contaminants either into solution or by 171 resuspension. Between L1 and L2 levels (0.3 -0.8 µgCdg -1 ) with low or no adverse outcome 172 from bioassays, sediment can be dumped in off-shores marine areas (over 3 m) or addressed 173 in confined disposal facilities (CDF) effectively isolated from the environment. An 174 environmental monitoring plan must be foreseen for each option listed above. Finally, above 175 the L2 levels, sediment must be dredged and transported with care, and effectively isolated 176 from the environment upon final disposal. 177

To determine the organic carbon content, the crushed sediment was acidified with 178 (Fisher Scientific, Analytical Reagent grade, 85%) to eliminate inorganic carbon. Then, the 179 samples were measured on a CHNS flash 2000 (Thermo Electron) following the method 180 described by Benner and Strom (1993). The total sulfur content was measured after mixing 181 around 3 mg of freeze-dried sediments with approximately 1.5 mg of vanadium pentoxide 182 V2O5 (Thermo Fisher Scientific). For both carbon and sulfur measurements, two reference soils 183 were used, NC and NCS (Thermo Fisher Scientific). Each sample was analyzed in triplicate. 184

The particle size distribution was determined using a laser diffraction particle-size 185 analyzer LS 13320 (Beckman Coulter Inc.). Wet sediment samples were dispersed in deionized 186 Automated measurements were controlled by the GPES 4.9 software (EcoChemie). 194 Quantification of the metals concentrations was performed using the standard addition 195 method, automated using syringe burettes (Pump XE 1000, TECAN). Voltammograms were 196 processed (peak height of 2 nd derivative as analytical signal characteristic) using ECDSOFT 197 software (Cobelo-García et al., 2014;Omanović and Branica, 1998). The percentage of Cd 198 desorption from sediment was calculated by subtracting the Cd quantity in the initial seawater 199 from the Cd quantity measured at the end of the experiment and divided by the quantity of 200 Cd added in the mixing solution by sediment particles. 201

III

Results and discussion 202

III.1 Sediment and seawater initial characteristics 203

The salinity of seawater was 37.9 for La Spezia, 37.6 for Olbia and 38.2 for Toulon, while 204 the pH values of overlying water for these three sites were 8. 32, 7.55 and 7.87, respectively. 205 The percentage of oxygen saturation of the overlying water was 89, 101 and 90.3 %. The initial 206 pH values of the seawater used for the resuspension experiments were 8.30, 8.36 and 7.79 for 207 La Spezia, Olbia and Toulon respectively. The initial dissolved Cd concentrations in seawater 208 were 15.74, 7.87 and 11.24 ngL -1 for La Spezia, Olbia and Toulon respectively, which is 209 consistent with the literature for these bays or their coastal surroundings (Breder, 1987;Coclet 210 et al., 2019). The dissolved Cd concentrations in the three harbors were below the admissible 211 dissolved cadmium concentration in seawater (more than 200 mgL -1 CaCO3) defined by the 212

EQS (2008/105/EC). 213

The sediment from La Spezia was equally composed of clay and sand (44 and 46 %) 214 while the silt fraction represented only 10 %. The sediment from La Olbia and Toulon were 215 mainly composed of clay (65 and 52 % respectively) while the sand fraction represented 28 216 and 40 % respectively. Finally, the silt fraction was the lowest one with only 7 and 8 % in the 217 sediment from Olbia and Toulon. 218 Cadmium contents were 0.10, 0.20 and 0.37 µgg -1 in the sediment of La Spezia, Olbia 219 and Toulon respectively. Contents observed in Toulon and Olbia sediments are consistent with 220 the literature for these bays (Schintu et al., 1991;Tessier et al., 2011) while the content 221 observed in La Spezia sediment were lower than that previously observed (Breder, 1987). The 222 easily-exchangeable proportion of Cd in the three sediments were 63, 47 and 38% for La Spezia,223 Olbia and Toulon respectively. Such range of easily exchangeable Cd proportion was already 224 observed in the literature (Dang et al., 2015a;El Houssainy et al., 2020). 225 The percentage of organic carbon in the sediment was 0.42, 2.12 and 2.39 % for La 226 Spezia, Olbia and Toulon respectively. The percentage of total sulfur was 0.

III.4 Kinetics of Cadmium transfers 282

First, Cd experienced a strong and fast removal from the dissolved phase, observed 283 within a few minutes (Figure 2A) for all experiments. As a consequence, dissolved 284 concentrations were decreased by a factor 15.3, 10.8 and 8.4 for La Spezia, Toulon and Olbia, 285 respectively (Figure 1B). Cd is known to have a strong affinity for carbonates and clays 286 (Pickering, 1983;Shirvani et al., 2006;Superville et al., 2015;Zheng et al., 2007), as well as 287 with OM (Tahervand and Jalali, 2016), therefore its removal might be attributed to its 288 adsorption onto resuspended carbonates, OM and/or clays. Dissolved Cd concentrations then 289 sediment:water ratio). Panel A represents its absolute variation while Panel B represents its relative 319 variation. As a consequence, a value above the black dotted line will correspond to an increase compared 320

to Cd in initial seawater, whereas a value below this line will correspond to a decrease. Note that the x 321 and y axis are on log scale. The dissolved Cd concentration indicated at x = 0.01 in panel A represents 322

Cd concentration of the initial seawater before the addition of sediment. 323

III.5

Effects of the quantity of resuspended particles onto cadmium transfers 324 Using a ratio of 2.5 gL -1 , we showed that the kinetics of Cd remobilization was similar 325 with different initial samples, and that the maximal dissolved Cd concentrations was observed 326 after 2 weeks of mixing. Therefore, we evaluated the impact of sediment resuspension 327 intensity after 2 weeks of mixing by varying the sediment:water ratio. The increase of 328 Sediment content in seawater (wet wieght g.L -1 ) Spezia Olbia Toulon MAC-EQS results clearly put forward the need to better characterize the processes leading to Cd 372 remobilization and controlling the magnitude of the contamination induced. An effort toward 373 mixing conditions better representing field conditions is now required to confront more 374 realistic data to regulation thresholds and to contribute to regulation harmonization between 375 countries. This study provides new bases for decision-makers and local authorities concerned 376 by sediment management and water quality protection. 377

Declaration of competing interest 378

The authors declare that they have no known competing financial interests or personal 379 relationships that could have appeared to influence the work reported in this paper. 380

  water and briefly treated in an ultrasonic bath (3 min) prior to measurement. The instrument 188 analysis ranged from 0.4 to 2000 μm. 189 Dissolved Cd concentrations in UV-irradiated seawater samples were determined by 190 Differential Pulse Anodic Stripping Voltammetry (DPASV). The measurements were carried 191 out using an Autolab-III potentiostat (EcoChemie) equipped with an autosampler. A three-192 electrode system (663 VA Stand, Metrohm) consisting of Hg working electrode (size 3), 193 Ag|AgCl|3 M KCl reference electrode and Pt counter electrode was used for measurements. 194

275 276Figure 1 :

 2751 Figure 1: Variations of pH during sediment resuspensions (2.5 gL -1 sediment :water ratio). Panel A 277 represents its absolute variations, with initial values of seawater represented by the symbols on the Y 278 axis line while panel B represents its variations relatively to the initial pH of seawater before sediment 279 addition. As a consequence, a value above the dotted line corresponds to an increase compared to the 280 initial sampled seawater value, whereas a value below this line corresponds to a decrease. No pH data 281 could be recorded for Toulon at 5 minutes of mixing because of a technical problem. 282

  at low concentrations up to 7 hours to 1 day of mixing. Finally, 291 dissolved Cd concentrations increased to reach maximal and stable values after one week 292 (Figure2A), showing that dissolved Cd dynamics were similar in the three experiments. Such 293

Figure 2 :

 2 Figure 2 : Variations of dissolved Cd concentration during sediment resuspensions (2.5 gL -1 319sediment:water ratio). Panel A represents its absolute variation while Panel B represents its relative 320 variation. As a consequence, a value above the black dotted line will correspond to an increase compared 321to Cd in initial seawater, whereas a value below this line will correspond to a decrease. Note that the x 322 and y axis are on log scale. The dissolved Cd concentration indicated at x = 0.01 in panel A represents 323Cd concentration of the initial seawater before the addition of sediment. 324

Figure 3 :

 3 Figure 3 : Variations of dissolved Cd as a function of the sediment content (wet weight in gL -1 ) in 354 seawater. The red dotted line represents the maximum allowable concentration (MAC-EQS) defined by 355 the Environmental Quality Standards (EQS) in seawater. Both axis are presented in log scale to better 356 visualize data. 357 IV Conclusion

(

  dredging activities) resuspension energies. Finally, the measured dissolved Cd 68 concentrations in the second set of experiments was compared to the maximum allowable 69 concentration (MAC) accepted by the EU-WFD EQS. avoid contamination, sampling devices, bottles, filters and syringes were 73 previously acid-cleaned (10% v/v HCl, pro analysis, Fisher Scientific) and fully rinsed with 74 Milli-Q water (18.2 MΩ, Millipore) at laboratory. 75 For the purpose of this work, sampling campaigns were performed in three 76 Mediterranean urbanized bays: La Spezia (coordinates 44.10482 N, 9.84737 E), Olbia 77 (coordinates 40.92944 N, 9.52812 E) and Toulon (coordinates 43.11454 N, 5.88542 E). The water 78 depth was 12, 4 and 1.4 m for La Spezia, Olbia and Toulon, respectively. At each sampling 79 site, 25 L of surface seawater (0.5 m) were collected using a 4.2 L horizontal van Dorn type 80 water sampler (Wildco, model Beta) and stored in a pre-cleaned 25 L HDPE bottle rinsed 3 81 times with water from the site. An aliquot of each seawater sample was filtered (0.2 µm on-82 line syringe filters, cellulose nitrate, Sartorius) and collected into a 125 mL FEP bottle, then 83 acidified (0.2%v/v HNO3 s.p (Merck)) before being UV-irradiated (150 W mercury lamp, 84

  water and briefly treated in an ultrasonic bath (3 min) prior to measurement. The instrument 187 analysis ranged from 0.4 to 2000 μm. 188 Dissolved Cd concentrations in UV-irradiated seawater samples were determined by 189 Differential Pulse Anodic Stripping Voltammetry (DPASV). The measurements were carried 190 out using an Autolab-III potentiostat (EcoChemie) equipped with an autosampler. A three-191 electrode system (663 VA Stand, Metrohm) consisting of Hg working electrode (size 3), 192 Ag|AgCl|3 M KCl reference electrode and Pt counter electrode was used for measurements. 193

Figure 2 :

 2 Figure 2 : Variations of dissolved Cd concentration during sediment resuspensions (2.5 gL -1 318sediment:water ratio). Panel A represents its absolute variation while Panel B represents its relative 319 variation. As a consequence, a value above the black dotted line will correspond to an increase compared 320to Cd in initial seawater, whereas a value below this line will correspond to a decrease. Note that the x 321 and y axis are on log scale. The dissolved Cd concentration indicated at x = 0.01 in panel A represents 322Cd concentration of the initial seawater before the addition of sediment. 323

Figure 3 :

 3 Figure 3 : Variations of dissolved Cd as a function of the sediment content (wet weight in gL -1 ) in 353 seawater. The red dotted line represents the maximum allowable concentration (MAC-EQS) defined by 354 the Environmental Quality Standards (EQS) in seawater. Both axis are presented in log scale to better 355 visualize data. 356 IV Conclusion

  supported by SE.D.RI.PORT. (SEdimenti, Dragagi e RIschi PORTuali, 382 Interreg Marittimo IT/FR 2017-2020, co-funded by European Regional Development Fund). 383 This work was realized also as a part of the project "New methodological approach in 384 biogeochemical studies of trace metal speciation in coastal aquatic ecosystems" (MEBTRACE) 385 (IP-2014-09-7530), financially supported by the Croatian Science Foundation. N. Layglon PhD 386 was partly funded by Sud region and supported by LASEM Toulon. 387 Pasero and Alexis Canino for their help regarding the sampling as well as Christian Martino 390 for instrumentation repairs. The authors are thankful to the ARPAL and ISPRA institutions as 391 well as the Olbia's mussel cooperative for the organization of the sampling campaign in Italy. 392 This work is dedicated to our colleague and friend Cédric Garnier, prematurely gone. 393 394 395

Table 1 :

 1 Mass of sediment particles added in the performed experiments 151

	Performed Experiment	Mass of added particles in La Spezia experiments (g)	Mass of added particles in Olbia experiments (g)	Mass of added particles in Toulon experiments (g)
	Kinetics (2.5gL -1 )	8.10	6.90	6.00
	Solid/Liquid ratio (0.05gL -1 )	0.02	0.01	0.01
	Solid/Liquid ratio (0.125gL -1 )	0.04	0.03	0.03
	Solid/Liquid ratio (0.25gL -1 )	0.08	0.07	0.06
	Solid/Liquid ratio (0.5gL -1 )	0.16	0.14	0.12
	Solid/Liquid ratio (1.25gL -1 )	0.41	0.35	0.3

Table 1 :

 1 Mass of sediment particles added in the performed experiments 150

	Performed Experiment	Mass of added particles in La Spezia experiments (g)	Mass of added particles in Olbia experiments (g)	Mass of added particles in Toulon experiments (g)
	Kinetics (2.5gL -1 )	8.10	6.90	6.00
	Solid/Liquid ratio (0.05gL -1 )	0.02	0.01	0.01
	Solid/Liquid ratio (0.125gL -1 )	0.04	0.03	0.03
	Solid/Liquid ratio (0.25gL -1 )	0.08	0.07	0.06
	Solid/Liquid ratio (0.5gL -1 )	0.16	0.14	0.12
	Solid/Liquid ratio (1.25gL -1 )	0.41	0.35	0.3

Table 2 .

 2 35, 0.91 % and 227 0.27 % in La Spezia, Olbia and Toulon respectively. 228 Given that the sediments were sampled in France and Italy, we compared their Cd 229 contents to national laws framing marine sediment management. Sediment from Toulon 230 presented Cd content lower than the regulatory N1 level defined by the French authorities 231(JORF n°184 10-08-2000). As a consequence, its potential impact regarding Cd is considered 232 neutral or negligible and the management of the sediment does not require any particular 233 precaution. The Cd content in La Spezia and Olbia were below the Italian lower chemical 234 exceedance Level and could thus be dredged, transported and disposed if the release of 235 The input of particulate Cd was 1.6-2.8 times higher in Toulon 241 experiments compared to that of Olbia and La Spezia and the exchangeable fraction was 1.3-242 1.7 times higher in Toulon experiments compared to that of Olbia and La Spezia. 243

	236	contaminants into solution or by resuspension is minimized (Italian Ministerial Decree
	237	173/2016).
	238	III.2	Quantity and partitioning of Cd from resuspended sediments in the different
	239	experiments
	240	The amount of total particulate and easily-exchangeable Cd added in each experiment
		are given in

Table 2 :

 2 Amount of total particulate and easily-exchangeable Cd expressed in ng added in each

	244
	245	performed experiment

Acknowledgments 389

The authors want to thank Erwan Tessier, the French Navy, Aurélie Portas, Emilie

Acknowledgments 388

The authors want to thank Erwan Tessier, the French Navy, Aurélie Portas, Emilie

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.


Olivier Barge

Jacques Élie Brochier

Jwana Chahoud

Christine Chataigner

Emmanuelle Régagnon

Wael Abu-Azizeh

Rémy Crassard

W Régagnon

R Abu-Azizeh

Crassard

A Betts

P Van Pelt

Hunting with kites in Armenia

Access in recent years to high-resolution satellite imagery via online platforms such as Google Earth and Bing Maps has provided a wealth of information for many scientific subjects, among them archaeology. In the years following 2010, comprehensive satellite coverage of the Near East and the Caucasus became available, enabling the discovery of large archaeological structures in remote and hard-to-reach areas. This has renewed scholarly interest in 'desert kites', huge structures apparent from above. In recent years the known number of kites has drastically increased to more than 5200 structures (31 December 2016).

, which profoundly reassessed their spatial extent.

In the case of Armenia, the project identified almost 200 kites on the lowest south-western slopes of Mount Aragats, in the western part of the country, which until this study were entirely unknown in the Caucasus. In the 1980s, a group of similar structures was discovered and studied considerably further north by [START_REF] Yagodin | Arrow shaped' structures in the Aralo-Caspian steppe[END_REF], on the Ustyurt Plateau of Kazakhstan and Uzbekistan. Excavation and surveys in 2013 permitted the Globalkites team to surmise that the Ustyurt kites were part of the wider kite phenomenon and shared many characteristics with the Aragats kites [START_REF] Barge | The 'desert kites' of the Ustyurt Plateau[END_REF]. This raised important questions about the overall role of the Armenian kites within the wider kite phenomenon, and the part they played in the potential diffusion of kite construction and use. Most importantly, the structures may provide a link between the Ustyurt kites and those of the Near East, despite their vast separation in space. A firm grasp of kite chronology is clearly of paramount importance if one wants to establish any such links, but unfortunately many uncertainties remain because few Near Eastern and Central Asian kites have been reliably dated (Zeder et al. 2013: table 1).

This chapter discusses the discovery, distribution, morphology, and architecture of the Aragats kites. It uses a comparative approach to highlight the distinctive characteristics of the Armenian group, while at the same time reaffirming their embeddedness in the wider kite phenomenon. Chronology, function, and potential prey species are also touched upon.

Discovery

The first kites in Armenia were recorded in 2009 by geologist Arkadi Karakhanyan of the National Academy of Sciences of Armenia [START_REF] Karakhanyan | Seismic hazard assessment for the construction site of a new power unit of the Armenian NPP, WP 6. Assessment of surface faulting potential[END_REF]. Fieldwork by the Globalkites project in 2011 established that these structures possessed all the necessary kite components -drivelines, enclosures, and cells -and allowed investigators to draw a preliminary map validating satellite observations. This initial campaign was followed by three further seasons in 2012, 2013, and 2015 that included archaeological excavation. An independent team from the University of Haifa simultaneously explored a set of kites located at the eastern end of the distribution area of the Aragats kites [START_REF] Nadel | New insights into desert kites in Armenia: the fringes of the Ararat Depression[END_REF].

Distribution: a dense and isolated entity

The Armenian kites are a long way from other groups of kites elsewhere in the Middle East and Central Asia. They are located 415 kilometres from the kites of the Jazira region of Upper Mesopotamia, and 850 kilometres from those of the Ustyurt Plateau (Figure 4.1). High-resolution satellite images have not revealed any desert kites in the areas in between despite meticulous searches for them. It is possible that a number of kites in these regions are not visible on satellite images due to their poor state of preservation, or because they insufficiently contrast with their environment. It is, however, also not unreasonable to think kites are effectively absent here, since they are easily identifiable on the slopes of the Aragats. The satellite images used are of the same quality, with equivalent resolution, and the environmental context of the regions under investigation is comparable in terms of geology, vegetation, and occupation. The Aragats kites should, therefore, be considered an isolated group.

The Aragats group is not only remarkable for its location, but also for the density of its kites. So far, 192 structures have been identified, lying within a depression measuring approximately 50 kilometres north-south and 40 kilometres east-west, covering an area of 1200 square kilometres. This means that the group has one of the highest densities of desert kites among their general distribution, comparable to that of the Harrat al-Shaam in north-east Jordan and the Harrat Khaybar in western Saudi Arabia (Figure 4.1). The Armenian kites are located in western Armenia (Plate 4.1), on the south and south-west basalt slopes of Mount Aragats at altitudes between 900 and 1600 metres, which are relatively low elevations in the regional context. They are all found not far from the modern cultivated plains they overlook. It is possible that kites were originally also constructed on these plains, but, if so, their traces have now been erased by cultivation. There is a high density of kites in the west of the area, with linear-arranged groups in the south and halo-shaped groups in the north-west. These arrangements can be explained from the observation that the kites run along the downstream eroded fringes of lava flows. In three-quarters of the kites, the break in the slope of this eroded flow-front was chosen for the entrance of the kite. Drivelines here extend onto the flat, slightly inclined and regular surface of the flow, while the enclosure is built downhill in the lava flowfront's chaotic and sloping topography (Figure 4.2). Rocky outcrops are often included within the enclosed space, as if it were necessary for the latter to have a high topographic complexity. This recurrent placement of the kites -along the eroded fringes of old lava flows, at low altitudes, and in close proximity to the plain -is characteristic of the Aragats group.

The orientation of the kites generally follows the orientation of the slopes on which they are built, with enclosures being located downslope and facing uphill (Figure 4.3) [START_REF] Brochier | Kites on the margins: the Aragats kites in Armenia[END_REF]. However, there are several exceptions in the west of the area (Plate 4.1), where kite entrances, even when they are built on the break of a slope, face downhill. Most kites are oriented west/north-east. This orientation may simply reflect the slope of the region (Plate 4.1) but could also be related to animal migration routes. Only a fraction of kites form linear arrangements with similarly oriented entrances (Plate 4.1), and the majority of these are not connected with their closest neighbour. In contrast to kites in the Jordanian Harrat al-Shaam [START_REF] Betts | Prehistoric sites at Qa'a Mejalla, eastern Jordan[END_REF]Kempe and Al-Malabeh 2013: fig. 5;Barge et al. 2015b: fig. 2, 3, 8) and certain kites on the Ustyurt Plateau [START_REF] Yagodin | Arrow shaped' structures in the Aralo-Caspian steppe[END_REF]Yagodin et al., this volume), the Aragats kites are not organised in true 'chains'; that is, they are not physically connected to one another, with the same opening orientation.

Construction: a specific morphology?

In most cases high-resolution satellite images enable a basic recording of individual kites, including the total number and length of their drivelines, the surface area of their enclosure, and the number and distribution of their cells. These data were collected for all Armenian kites for which this was possible, amounting to a total of 162 (out of 192) structures. Similar data were obtained for a sample of 600 kites, representative of their entire area of distribution from Arabia, the Near East, and Central Asia, so that the Armenian group could be compared against the wider kite population.

DRIVELINES

The drivelines of Aragats kites consist of continuous low walls that are only a single course high. The walls are of simple dry-stone construction and are, on average, about 50 centimetres wide and only a few decimetres high. The absence or low volume of collapse suggests that the walls would not have been much higher when the kites were in use. This feature, which is not unique to the Aragats kites, demonstrates that low walls would have been sufficient to drive animals. In most cases kites have two drivelines (Figure 4.4a). Kites with no or only one driveline are rare, but occur with a slightly greater frequency in Armenia than elsewhere. Field surveys have shown that the lack of drivelines on satellite images indeed reflects true absence. It cannot be excluded that some of these structures would have had temporary drivelines or drivelines made of perishable materials. However, in most cases natural features in the area, such as abrupt slopes, would have functioned as a driveline. Most kites without drivelines have their enclosure located upslope, facing downhill, which is contrary to normal placement. Kites with more than two drivelines are rare. The Aragats drivelines are relatively short when compared to those of the global sample (Figure 4.4b).

Most often they are a few hundred metres long. Some examples are only tens of metres long. There are no drivelines that are several kilometres long, as for instance in Jordan or northern Arabia (Barge et al. 2015a: fig. 5).

ENCLOSURES

The simple dry-stone enclosure walls are, as a rule, higher and wider than those of the drivelines, sometimes reaching two metres in height and 1.2 metres in width. Enclosures normally have a roughly circular (case AM64, with a cell at the terminal end (so-called pointed cells) are especially frequent. In most cases, enclosures have a pointed cell on one or two sides of the entrance (cases AM14 and AM15). Sometimes enclosures have a double pointed cell at this location (cases AM64 and AM4).

The surface areas of Aragats enclosures tend to be greater than those of enclosures in the broader data set (Figure 4.4c), often exceeding a hectare. Median surface areas are slightly over two hectares. On average the enclosures contain 3.1 cells, which is quite small in relation to the kites of the broader data set, which have more than twice that number. Pointed cells are the most numerous, making up 40 per cent of the cells in the broader data set, and 77 per cent in the case of the Armenian data set.

In sum, whatever variable is taken into account in the comparisons, the Aragats kites are distinctive in combining few and short drivelines with a large-sized enclosure containing a small quantity of cells, most of which are of a pointed type.

CELLS, THE REAL FEATURES FOR TRAPPING ANIMALS

The Aragats kites have two types of large cells: circular, with a mean surface area of 16 square metres, and quadrilateral, with a much greater mean surface area of 31 square metres. Cell walls are usually faced on both sides and have several While kites have sometimes been considered enclosures meant to gather domesticated animals, or those well on the way towards husbandry [START_REF] Échallier | Nature et fonction des 'desert kites': données et hypothèses nouvelles[END_REF], the function of cells has not been explored in detail. Most initial interpretations considered them to be hunters' hideouts, but excavation has since shown that many cells are deep, pit-like constructions. The care given to the internal facing of these pits is particularly remarkable, and is a constant feature across the various regions explored by the Globalkites team, be it Armenia, Jordan, Kazakhstan, or Saudi Arabia. Excavations have shown that the floors of cells are always located below the enclosure floor. The difference in elevation between the two can exceed four metres in Armenia, making them functional trapping pits. Two techniques were employed in cell construction. The first consisted of digging a pit into the substratum until the desired depth was reached, and lining the sides of the pit with a facing of fieldstones. Above floor level, a much lower second facing of stone was subsequently built around the edge of the pit (AM14-L01 cell: Figures 4.9 and 4.10). The second technique took advantage of the topography and inserted the cell just below a slope break. In this example a low wall was built on the side of the enclosure at the slope break, with the depth of the cell being obtained by making use of the slope's natural gradient. An external wall was then added with a double facing. This wall was often of considerable height and width, but is rarely entirely preserved (cell AM15-L03: Figures 4.9 and 4.10).

Cells are most often located at the terminal ends of enclosure protrusions, sometimes constructed along slope breaks. Their general shape is identical to the cells in 'V-shaped' or 'killing kites' in the Negev [START_REF] Holzer | Desert kites in the Negev desert and northeast Sinai: their function, chronology and ecology[END_REF][START_REF] Nadel | Walls, ramps and pits: the construction of the Samar desert kites, southern Negev, Israel[END_REF][START_REF] Nadel | Ramparts and walls: building techniques of kites in the Negev Highland[END_REF]. The Armenian kites described by [START_REF] Nadel | New insights into desert kites in Armenia: the fringes of the Ararat Depression[END_REF] at the eastern end of the distribution of Armenian kites are plausibly only pointed cells that have had their associated enclosures destroyed. Kites in the east of the Mount Aragats group have been heavily disturbed by multiple later destructions or refurbishments. Many of these alterations and destructions seem to be modern, although some are evidently older, a feature confirmed in the field. To us, the resemblance of these structures, which are otherwise unique in the large Armenian sample, to isolated structures in the distant Negev and Sinai, is coincidental, and the result of degradation rather than conscious planning.

ESTIMATING DATES OF CONSTRUCTION

The chronology of the Aragats kites, and desert kites generally, is poorly understood and represents a serious challenge to archaeologists. Desert kites commonly lack occupation layers with diagnostic archaeological remains, such as pottery fragments and other artefacts, which makes it difficult to determine who was responsible for their construction and use. However, in the last decades, thanks to advancements in radiocarbon-dating techniques, such as the widespread use of measurements in accelerators (AMS) on very small quantities of organic material, some absolute chronological benchmarks have been obtained. Despite great investment in the field, we were only able to obtain radiocarbon dates for six out of 192 Aragats kites (that is, little more than three per cent of the total corpus).

The dates presented in this chapter stem from residual radiocarbon found inside the cell fills, most often at low elevations. These dates only provide a terminus ante quem (TAQ) for the date of construction (Table 4.1). The materials used in most cases were tiny bird-eggshell fragments, extracted from the sandy fraction of the detritic sediment using a binocular microscope. Bone splinters, Boraginaceae calcitic nutlets (Buglossoides arvensis L.), and charcoal were also analysed when available. Eggshell fragments are a common (albeit scarce) datable biological carbonate in cell fills in Armenia and elsewhere. It is as if in these open landscapes, the inner dry-stone cell walls were used by small birds for nesting. Frequency counts indicate they do not occur in samples pre-dating construction; they are thus salient biomarkers of the beginning of cell infilling in a context marked by sedimentary homogeneity. Measured radiocarbon ages were validated by the geoarchaeological correlation of the different sequences according to the taphonomically complex -but uniform across Aragats' slopes -evolution of two groups of siliceous algae, aerophylous diatoms (Hantzschia amphioxys [Ehrenberg] Grunow), and chrysophytes (statospores), both linked to long-term changes of intensity in pastoralism [START_REF] Brochier | Kites on the margins: the Aragats kites in Armenia[END_REF].

Construction event TAQ are provided in Figure 4.11 and 4.1. They are rough estimations based on the contentious initial postulate that the ongoing infilling was never removed during use of the cells. Furthermore, the estimated mean sedimentation rate in these sediment traps (seven to 10 centimetres per century) means that in some cases the TAQ dates underestimate construction and use dates.

We therefore used all available prior knowledge to construct chronological models and estimate, through Bayesian modelling [START_REF] Buck | Combining archaeological and radiocarbon information: a Bayesian approach to calibration[END_REF][START_REF] Buck | Bayesian approach to interpreting archaeological data[END_REF], the main parameter of interest: the event of construction. These (unknown) events are introduced in the chronological models -one for each construction -as a uniform distribution defined on the whole study period. It is on these uninformative data that prior knowledge is entered into the Bayesian framework. The prior knowledge used falls into two types: 1) cell stratigraphy and stratigraphic relations between kites (for example, AM14 was constructed later than AM15), and 2) the first common use of the double-faced wall construction technique -used in all the Aragats kites -in Early Bronze Age Armenia, as modelled from 88 Chalcolithic and Early Bronze Age radiocarbon dates.

These results are more plausible, even if they may appear less accurate. One must bear in mind that, due to the common lack of on-site terminus post quem (TPQ) dates, the modelled construction dates have a likely bias toward older dates. Regardless, one can observe that the construction of these five radiocarbon-dated kites could not have occurred later than the beginning of the Common Era (the end of Iron Age IV), nor before the Chalcolithic-Early Bronze Age transition -this is a priori information used in the model. In the only case (AM4) that yielded, by chance, an on-site TPQ, the construction event took place in the Iron Age. As regards a potentially too old double-wall construction technique TPQ, one solution would be tentatively to place the construction and use of these structures between the Middle Bronze Age and Iron Age IV. This estimate would fit the AM106 OSL date obtained by Naomi Porat (in [START_REF] Nadel | New insights into desert kites in Armenia: the fringes of the Ararat Depression[END_REF] in a challenging environment.

It is difficult to determine if these radiocarbon dates can be projected onto the entire Aragats group. However, three clues support a relatively short period of use, being: the morphological uniformity of the Aragats kites, the unique way in which they adapt to landscape morphology, and the lack of modifications to initial designs.

Function: kites were hunting traps

On a functional level, most scholars have favoured the hypothesis that desert kites were used for hunting purposes. The idea that they were for pastoral use [START_REF] Échallier | Nature et fonction des 'desert kites': données et hypothèses nouvelles[END_REF] has been strongly dismissed [START_REF] Rosen | The function of 'desert kites': hunting or livestock husbandry?[END_REF]. Nevertheless, both hypotheses deserve further examination. Our multi-proxy approach is to a large extent an attempt to understand the function and workings of these vast structures [START_REF] Crassard | Addressing the desert kites phenomenon and its global range through a multi-proxy approach[END_REF]. Kites are easily recognised and now known to have been extremely numerous. However, the aims of their builders and methods of use are still relatively little understood. Two strands of shed further light on these matters. The first revolves around a study of the location, morphology, and architecture of the kites. The second is connected with the systematic excavation of cells.

The regular placement of Aragats kites seems to support the hunting hypothesis. The construction of drivelines oriented upwards on a slight slope, with the enclosure below being separated by an edge or threshold, is a salient characteristic of the Aragats kites. The presence of an edge or threshold is common, [START_REF] Helms | The desert 'kites' of the Badiyat Esh-Sham and North Arabia[END_REF]). This configuration is more appropriate for use as a demi-piège (a 'semi-trap', meaning a passive structure that needs to be 'activated' by human presence, Testart 1984) than for pastoral purposes. The vast size of the enclosure also points in this direction.

The interpretation of the orientation of the kite entrance is more difficult. Their location seems to be largely determined by the orientations of local slopes; and probably, on a smaller scale, by those of the volcano. The Aragats kites could thus have been constructed to intercept herds running downhill. Nevertheless, it has to be conceded that many kites open towards the west and the north-east, and would be well oriented to intercept seasonal migrations of large herbivores that still take place in the area [START_REF] Chahoud | Archaeozoological approach in understanding the 'desert kites[END_REF].

Cells are the most elaborately constructed elements of the Aragats kites, which suggests they must have played an important role in the functioning of the structures. This observation is valid not only for Armenia but also for kites elsewhere. The use of deep pits with high and corbelled walls suggests that they were used as trapping pits. The walls would have prevented animals from jumping out of the pits. The common enclosure protrusions almost surely served to drive animals towards the trapping pits.

These aforementioned observations all point to the kites being used for hunting and do not fit a pastoral interpretation. Nevertheless, there are still many uncertainties about how Armenian kites would have functioned. Enclosures often contain rocky outcrops, but the purpose of these is unknown. Perhaps they added a certain complexity to the terrain, making the interior and exterior of the enclosure seem identical, thereby masking the kite. Likewise, it is difficult to find a functional interpretation for the partition walls that are frequently observed within kite enclosures. Sometimes these block off pointed protrusions with cells at their terminal ends. Close scrutiny of these walls suggests that they were not later additions but built at the same time as the enclosure. Their presence seems to contradict the use of pointed cells for hunting.

In sum, even if the hunting function of the kites seems beyond reasonable doubt, many details of their inner workings are still poorly understood. This remark holds true not only for the Armenian desert kites but for all desert kites in the Middle East and Central Asia.

Prey species

It is difficult to determine what species were hunted with the use of desert kites [START_REF] Chahoud | Archaeozoological approach in understanding the 'desert kites[END_REF]. The rare bone remains found during excavation of the cells were in the upper horizons of the stratigraphic sequence and provide little information. A recent zooarchaeological analysis of prey species in Armenia during the Holocene [START_REF] Chahoud | The diversity of Late Pleistocene and Holocene wild ungulates and kite structures in Armenia[END_REF] suggests that wild species were rare from the Early Bronze to the Iron Ages. However, among them, four types of ungulates were present, all of which were potentially hunted with the use of kites: Bezoar goat (Capra aegagrus), mouflon or wild mountain goat (Ovis orientalis), red deer (Cervus elaphus), and, more specifically during the Iron Age, goitered gazelle (Gazella subgutturosa). According to historical and contemporary observations, kites are found along the migration routes of these animals and may have been used to intercept migrating game [START_REF] Chahoud | The diversity of Late Pleistocene and Holocene wild ungulates and kite structures in Armenia[END_REF]). Nevertheless, it is only through the discovery of zooarchaeological remains in the deepest layers of cells or associated features that direct evidence for prey species can be obtained.

Conclusion

The Aragats group consists of a dense and relatively uniform group of kites. A small number of radiocarbon dates suggests that at least some of the structures were constructed between the Armenian Bronze Age and the start of the Common Era. However, it is still unclear to what extent these dates can be projected onto other kites in the group. Despite initial fieldwork, many details about the inner workings of desert kites remain poorly understood. There are also a lot of unknowns when it comes to potential prey species, although the number of potential candidates appears to be limited, based on indirect evidence. We are hopeful many of these facets will be elucidated soon through further fieldwork.

More difficult, and perhaps more fundamental for researchers interested in past societies, is the study of the social, economic, and symbolic importance of the Aragats kites. A broad archaeological outline has been established for the region [START_REF] Badalyan | Bronze Age and Early Iron Age archaeological sites in Armenia 1: Mt Aragats and its surrounding region[END_REF][START_REF] Badalyan | Village, fortress, and town in Bronze and Iron Age southern Caucasia: a preliminary report on the 2003-2006 investigations of Project ArAGATS on the Tsaghkahovit Plain, Republic of Armenia[END_REF], and this should help us to better understand the cultural dimension of the kite phenomenon.

Figure 4 . 1 .

 41 Figure 4.1. Distribution and density of desert kites (number of kites by meshes 50 km wide).

Figure 4 . 2 .

 42 Figure 4.2. Oblique aerial photographs of kites AM7 (a) and AM67 (b) with schematic kite representations in the insets.

Figure 4 . 3 .

 43 Figure 4.3. Distribution and Gaussian kernel smoothing of angular differences between the opposite directions towards which the kites open and the mean of the directions towards which the local slopes are oriented.

  Figure 4.4a. Comparison of morphological variables for the Aragats kites (n = 162), and those of a sample covering the area of extension in a homogenous way (n = 600). Number of drivelines.

Figure 4 . 5 .

 45 Figure 4.5. Plan of kite AM67.

Figure 4 .

 4 Figure 4.4c. Comparison of morphological variables for the Aragats kites (n = 162), and those of a sample covering the area of extension in a homogenous way (n = 600). Enclosure surface area (Tukey box plot, outliers omitted, max-min shown as dot).

Figure 4 . 6 .

 46 Figure 4.6. Plan of kites AM14 and AM15. Excavated cells are highlighted in blue.

Figure 4

 4 Figure 4.7. Hill-shade of kite AM4 from a Digital Surface Model obtained with aerial photogrammetry. Note the presence of two different types of cells: cells dug into the substratum and slope break cells.

Figure 4 . 8 .

 48 Figure 4.8. Examples of cells: A. circular cell from AM7 kite; B. rectangular cell from AM10 kite; C. cell AM14-L01, dug into the substratum; D. cell AM67-L01, dug into the substratum; E. cell from AM5 kite, built using a slope break; F. cell from AM1 kite, built using a slope break. (Photographs by Olivier Barge and Jacques Élie Brochier)

Figure 4 . 9 .

 49 Figure 4.9. Cells AM14-L01 and AM15-L03 in section. The current topographical profile is indicated in black. The reconstruction of the walls is theoretical and does not take the corbelling into account.

Figure 4 .

 4 Figure 4.10. Plan of cells AM14-L01 and AM15-L03. The location of the sections depicted in Fig. 10 is indicated by a dashed line.

Acknowledgements

We wish to thank Alison Betts for her kind invitation to present our results from Armenia in this book. The Globalkites project is financed by the French National Research Agency (No. ANR-12-JSH3-0004-01, to Rémy Crassard). Fieldwork in Armenia has benefited greatly from the help of the 'Mission Caucase' team, funded by the French Ministry of Foreign Affairs (to Christine Chataigner). We thank Arkadi Karakhanyan, Iren Kalantaryan, Arthur Petrosyan, Pavel Avetisyan and Makoto Arimura for extremely helpful assistance in Armenia.

Plate 4.1. Location and orientation of the Aragats kites.