Edouard Leaune
email: edouard.leaune@ch-le-vinatier.fr

Maeva Samuel

Hans Oh

Emmanuel Poulet

Jérôme Brunelin

Suicidal behaviors and ideation during emerging viral disease outbreaks before

Keywords: Conceptualization, Methodology, Investigation, Conceptualization, Supervision, Writing -Review

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

INTRODUCTION

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also known as the Corona Virus Disease 2019 , first appeared in Wuhan, China, in November 2019 [START_REF] Spiteri | First cases of coronavirus disease 2019 (COVID-19) in the WHO European Region, 24[END_REF]. Since then, COVID-19 has spread across the world, on all continents, leading The World Health Organization to officially declare the COVID-19 outbreak a pandemic [START_REF] Spiteri | First cases of coronavirus disease 2019 (COVID-19) in the WHO European Region, 24[END_REF]. Currently, there have been more than 850,000 reported deaths from COVID-19 infection and more than 25,000,000 reported cases worldwide (WH0, 2020).

The COVID-19 pandemic is thus considered to be the most severe pandemic of the 21 st century, on track to having a rising death toll.

Beyond causing respiratory symptoms and distress that lead to death, COVID-19 may also cause direct and indirect mortality by way of suicide [START_REF] Chevance | Ensuring mental health care during the SARS-CoV-2 epidemic in France: a narrative review[END_REF]Gunnell et al., 2020;[START_REF] Reger | Suicide mortality and coronavirus disease 2019 -A perfect storm?[END_REF]. On March and April 2020, the first cases of COVID-19-related suicides were reported in India and Bangladesh when two men who feared having contracted the disease took their own lives (Goyal et al., 2020;[START_REF] Mamun | First COVID-19 suicide case in Bangladesh due to fear of COVID-19 and xenophobia: possible suicide prevention strategies[END_REF].

Moreover, recent editorials hypothesized an increased suicide risk associated with the COVID-19 pandemic (Gunnel et al., 2020;[START_REF] Holmes | Multidisciplinary research priorities for the COVID-19 pandemic: a call for action for mental health science[END_REF]Klomek, 2020) and previous studies informed the putative association between viral infectious diseases and deaths by suicide [START_REF] Catalan | HIV infection and mental health: suicidal behaviour--systematic review[END_REF][START_REF] Lund-Sørensen | A nationwide cohort study of the association between hospitalization with infection and risk of death by suicide[END_REF]. A nationwide Danish study for example reported a significant and strong association between viral infection during hospitalization and deaths by suicide, with the number of days treated for infection being associated with elevated risk for suicide in a dose-response fashion [START_REF] Lund-Sørensen | A nationwide cohort study of the association between hospitalization with infection and risk of death by suicide[END_REF]. However, the pathways by which emerging viral disease outbreaks (EVDOs) and suicide may be related are complex and not entirely understood.

First, EVDOs are associated with psychosocial and emotional aspects (e.g., fear of infection, stigma of being diagnosed with infection, cancellation of "non-emergency" hospitalizations) that may drive risk for suicidal ideation and suicide attempts [START_REF] Reger | Suicide mortality and coronavirus disease 2019 -A perfect storm?[END_REF].

The social distancing and quarantine measures that have been enacted to curb the spread of the disease have resulted in increased loneliness, anxiety, stress, and depression in the general population [START_REF] Rajkumar | COVID-19 and mental health: A review of the existing literature[END_REF][START_REF] Wang | Immediate psychological responses and associated factors during the initial stage of the 2019 Coronavirus Disease (COVID-19) Epidemic among the general population in China[END_REF]. EVDOs also result in economic downturns, causing unemployment and general instability that has been associated with numerous health problems, including increased deaths by suicide [START_REF] Oyesanya | Systematic review of suicide in economic recession[END_REF].

Second, viruses exhibit neurotrophic properties and can cause severe neurological damage and nervous diseases (e.g., toxic infectious encephalopathy) that cause mental disorders (Toovey et al., 2020;[START_REF] Wu | Nervous system involvement after infection with COVID-19 and other coronaviruses[END_REF]. In some cases, viral infections can cause disorientation, dysphoria, confusion, and delirium, which in turn lead to suicidal ideation and behaviors [START_REF] Chevance | Ensuring mental health care during the SARS-CoV-2 epidemic in France: a narrative review[END_REF][START_REF] Reger | Suicide mortality and coronavirus disease 2019 -A perfect storm?[END_REF]Severance et al., 2008).

These factors taken together likely increase risk for suicidal ideation and behaviors during EVDOs; however, to our knowledge, there has been no review of literature published on the topic thus far. In the current context, it is imperative to systematically review past research in order to prevent the negative impacts of the emerging pandemic and do as much as possible to reduce all deaths that are linked to the outbreak, including death by suicide. A rapid systematic review on the topic is thus urgently needed, to immediately inform prevention strategies during and beyond the COVID-19 pandemic. The aim of our study was to systematically review the evidence on the association between EVDOs and suicidal ideation and behaviors.

METHODS

Systematic research

The review protocol was based on the PRISMA guideline for systematic reviews [START_REF] Liberati | The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration[END_REF] and previous rapid reviews [START_REF] Tricco | A scoping review of rapid review methods[END_REF]. The search was conducted between April 7 th and April 11 th , 2020, on the five following databases: Medline, Embase, Web of Science, PsycINFO and Scopus, using the following search terms, grouped into three categories as follows: To ensure the exhaustivity of the search and the relevance of the algorithm, a pilot electronic search was performed between April 3rd and April 6 th , 2020. The results of the pilot search were reviewed and the search terms and algorithm were further refined. Moreover, the electronic search was supplemented with a manual search using the reference lists of relevant publications. Corresponding authors of articles were contacted if necessary.

Inclusion criteria

Inclusion criteria were (a) articles published in peer-review journals in the English, French or German language; (b) articles published since inception until April 7 th , 2020; (c) articles assessing the prevalence or incidence of suicidal ideation and/or suicide attempts and/or deaths by suicide; (d) articles assessing these outcomes during or in the aftermath of an EVDO. No geographic or age restrictions were applied for the electronic research. Regarding the methodology of articles, editorials, correspondences, systematic reviews and single case reports were excluded.

Based on the Columbia Classification Algorithm of Suicide Assessment (C-CASA) [START_REF] Posner | Columbia Classification Algorithm of Suicide Assessment (C-CASA): classification of suicidal events in the FDA's pediatric suicidal risk analysis of antidepressants[END_REF][START_REF] Turecki | Suicide and suicidal behaviour[END_REF], we differentiated suicidal ideation and suicidal behaviors, which were defined as a) suicide attempts and b) deaths by suicide.

Selection process

Two authors (EL and MS) performed the electronic search on April 7 th , 2020. The studies identified through the databases were then subjected to three selection filters between April 8th and 11th, depending on the titles, abstracts, and a comprehensive full-text reading of each selected paper thereafter. At each stage, the two authors independently screened all the selected articles, and identified those for which available data (title for the first stage, abstract for the second and then full-text) were consistent with the inclusion criteria of the review.

After each stage, the two authors discussed their selections and agreed upon the articles to retain. When discrepancies arose, the choice to include or exclude an article was discussed with other co-authors (JB and HO).

Quality of reporting evaluation

Two authors (EL and MS) assessed the quality of included studies according to the STROBE statement (Strengthening the Reporting of Observational Studies in Epidemiology) [START_REF] Von Elm | The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies[END_REF]. The level of quality was as follows: very good quality (26-32); good quality (20-26); average quality (14-20); and poor quality (<14).

Data analysis

A systematic review was carried out, which involved separately and independently extracting quantitative data by the two first authors (EL and MS) for each of the outcomes. We extracted from each article the name of the first author, the year of publication, the design of the study, the country of the study, the sample and characteristics of participants and the main results reported by the authors regarding the association between EVDOs and suicidal ideation and behaviors (e.g., prevalence or incidence during the epidemic or post-epidemic periods, risk factors, at-risk populations). The extracted data were then grouped and the evidence was summarized for each outcome. All discrepancies were discussed, and consensus was reached across all authors on the final summary. No meta-analysis was planned as the number of included studies was expected to be low and their outcomes heterogeneous.

RESULTS

The electronic search yielded a total of 2,480 articles. After removal of duplicates and the application of selection filters, 9 articles [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF][START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF][START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF]Okasuga et al., 2011;[START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF][START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF] met the inclusion criteria (Figure 1).

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Characteristics of included articles

Most of the data were collected in Hong Kong (n = 3) [START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] and the USA (n = 3) [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF]Okasuga et al., 2011;[START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF]. All studies were observational, with samples ranging from 66 to 87,486,713.

Publication dates ranged from 1992 to 2019. Four of the articles dealt with the 2003 Severe Acute Respiratory Syndrome (2003 SARS) [START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] outbreak, four with influenza outbreaks [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF][START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF], Okasuga et al., 2011;[START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF] and one with the 2013-2016 Ebola virus disease in Guinea [START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF]. The studies assessed the prevalence of deaths by suicide (n = 5) [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF][START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] or suicide attempts (n = 4) [START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF]Okasuga et al., 2011;[START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF][START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF]. Of them, 5 studies retrospectively assessed the prevalence of deaths by suicide [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF][START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] or suicide attempts [START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF] during and/or after EVDOs (Okasuga et al., 2011;[START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF]. [START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] retrospectively examined the characteristics of SARS-related suicides versus non-SARS-related deaths by suicide that occurred in 2003 in Hong Kong. Only one study longitudinally assessed the presence of suicidal ideation and suicide attempts in a post-epidemic period [START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF]. The characteristics of the included studies are displayed in Table 1.

PLEASE INSERT TABLE 1 ABOUT HERE

Change in rates of deaths by suicide (n= 4)

The four studies [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF][START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] reported an increase in deaths by suicide during three different EVDOs (Table 1). Two studies [START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] reported a slight but significant increase in suicide rates in older adults in Hong Kong during the 2003 SARS outbreak. [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF] and [START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF] reported increased suicide rates in the general population during two influenza outbreaks, respectively in the USA during the 1918 influenza outbreak and in Europe (United Kingdom, Ireland and France) during the 1889-1894 Russian influenza outbreak.

Change in rates of suicide attempts (n =1)

Huang et al. ( 2005) reported a non-significant increase in emergency department visits for suicide attempts (drug overdoses) during the peak of the 2003 SARS epidemic in Taiwan.

Time of the outbreak

Epidemic peak (n= 4)

The increase in suicidal behaviors was mainly reported during the peak of the epidemic [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF]. [START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] found an excess in older adults' suicide rates at time of the epidemic peak of the 2003 SARS outbreak. [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF] reported a peak in deaths by suicide in the US general population during the Great Influenza Epidemic occurring at the end of the peak of the flu epidemic in 1919. [START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF] reported a non-significant increase in emergency department visits for suicide attempts (drug overdoses) during the peak of the 2003 SARS epidemic in Taiwan.

Late and post-epidemic periods (n= 3) [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] reported the maintenance of higher suicide rates in older adults in the year after the 2003 SARS outbreak. Similarly, [START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF] reported the persistence of occurrence of suicide attempts five, eleven, and twelve months after discharge from Ebola Treatment Centers. On the other hand, [START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF] found no increase in emergency department visits due to suicide attempts in the late-and post-epidemic period of the 2003 SARS outbreak.

Sociodemographic characteristics

Age of participants (n= 2)

In the study by [START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF], the increase in the rates of suicide was significant for older adults (>65) but not for people under 65 in Hong Kong. One study [START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF] assessed the association between influenza infection and suicide attempt in people under 18 and found no significant association.

Gender of participants (n= 2)

Chan et al. ( 2006) found the excess mortality by suicide to be significant for older females but not for older males during the peak of the 2003 SARS outbreak, while [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] did not find any gender differences in the same context.

Other characteristics (n= 1) [START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] found no significant differences in marital (married, single, divorced, widow or lived alone) or in socioeconomic status (employed, unemployed, retired, homemaker or received CSSA) between SARS-related and non-SARS-related suicides. [START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] and [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] identified four putative factors associated with SARS-related deaths by suicide: the fear of the infection, the experience of social isolation, the disruption of normal social life and the burden among those with long-term illnesses. The fear of contracting SARS was found to be the most significant risk factor by [START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF]. Regarding the fear of being infected, unusual concerns about hygiene and reluctance to receive medical care were identified as two factors implicated in death by suicide [START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF]. [START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] also reported the role of social disconnection as a risk factor for SARS-related suicides in older adults. [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] also identified high severity of chronic physical illness and high dependence as risk factors for suicide in older adults during the 2003 SARS outbreak. On the contrary, [START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] found no significant correlation between the level of dependence, the severity of illness, and SARS-related suicides in older adults.

Factors associated with suicidal behaviors during emerging viral disease outbreaks (n= 4)

Regarding psychiatric profiles, [START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF] found no significant association between previous psychiatric disorders and deaths by suicide in older adults during the SARS 2003 outbreaks. In their case-series analysis, [START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF] reported suicidal ideation and attempts associated with post-Ebola depressive disorders.

Regarding antiviral treatments, [START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF] found no significant association between oseltamivir consumption and suicide attempts in people under 18.

Type of virus

Coronaviruses (n= 2)

Two studies [START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] reported an increase of suicide rates during the 2003 SARS outbreak in Hong Kong, while Okasuga et al. (2011) found no significant association between coronavirus seropositivity and suicide attempts in the USA.

Influenza viruses (n= 4)

Okasuga et al. ( 2011) reported a significant and positive association between seropositivity for influenza B and suicide attempt but not for influenza A seropositivity in depressed individuals. [START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF] found no significant association between influenza infection and suicide attempts in people under 18. [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF] and [START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF] reported increased suicide rates during two influenza pandemics.

Ebola virus (n= 1) [START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF] reported in a case-series analysis of 256 survivors of the Ebola virus disease four cases of people experiencing suicidal ideation (n = 1) or having attempted suicide (n = 3) after their discharge from Ebola Treatment Centers.

Quality or reporting

The mean score at the STROBE checklist was 20.44 (SD = 4.14). Of the included studies, 8 were rated as good quality [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF][START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF]Okasuga et al., 2011;[START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF][START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF]. The article by [START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF] was considered as poor quality as the methodological characteristics of the study (e.g., population, outcome measures, statistical analyses) were not accurately reported.

DISCUSSION

Summary of findings

We performed the first systematic review on the impact of EVDOs on suicidal ideation and behaviors before the SARS-CoV-2 pandemic. First, we found the literature on the topic to be scarce but we found some weak evidence to suggest a significant increase in deaths by suicide during EVDOs. Second, older adults were reported to be particularly vulnerable to death by suicide during the 2003 SARS outbreak. Third, psychosocial factors such as the fear of being infected by the virus or social isolation related to quarantine measures were the most prominent factors associated with death by suicide during EVDOs. Fourth, on the contrary, we found only weak evidence to support the hypothesis that the neuropsychiatric symptoms induced by infection may explain the increased rates of suicidal behaviors during EVDOs.

We found scarce and weak evidence that suicidal behaviors increase during EVDOs [START_REF] Wasserman | The impact of epidemic, war, prohibition and media on suicide: United States, 1910-1920[END_REF][START_REF] Smith | The Russian Influenza in the United Kingdom, 1889-1894[END_REF][START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF][START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF]. However, there has been few studies conducted on the topic, especially regarding suicide attempts. Moreover, the strength of the association is relatively low. Indeed, several included studies reported non-significant results (e.g., [START_REF] Huang | Impact of severe acute respiratory syndrome (SARS) outbreaks on the use of emergency department medical resources[END_REF][START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Harrington | The relationship between oseltamivir and suicide in pediatric patients[END_REF], and the studies that reported positive results showed relatively small effects. For instance, the estimate IRRs reported by [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] and [START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF] among older adults ranged from 1.18 to 1.32, which may fall short of being clinically meaningful. However, the findings were consistent across studies and suicide prevention strategies are thus warranted during EVDOs.

Potential pathways

Psychosocial effects of EVDOs may be regarded as the main risk factors for an increase in suicidal behaviors according to our results. The fear of being infected by the virus was indeed reported in our review to be the most salient reason for suicide attempt during EVDOs (Goyal et al., 2020;[START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF], especially among older adults [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF]. This result is consistent with previous studies on emerging infectious diseases, such as HIV [START_REF] Vuorio | Eight cases of patients with unfounded fear of AIDS[END_REF][START_REF] Aro | Fear of acquired immunodeficiency syndrome and fear of other illness in suicide[END_REF][START_REF] Aro | Fear of AIDS and suicide in Finland: a review[END_REF][START_REF] Kausch | Irrational fear of AIDS associated with suicidal behavior[END_REF] or syphilis [START_REF] Savage | Fear of syphilis and suicide[END_REF] for which the fear of being infected was also found to be correlated with suicide ideation or attempts. Recently, deaths by suicide associated with the fear of being infected with the virus were reported during the current COVID-19 pandemic (Goyal et al., 2020;[START_REF] Mamun | First COVID-19 suicide case in Bangladesh due to fear of COVID-19 and xenophobia: possible suicide prevention strategies[END_REF].

Social isolation was also found in our review to be a significant risk factors for deaths by suicide during the 2003 SARS outbreak. Although none of the included articles directly assessed the impact of lockdown measures on suicidal behaviors, social isolation and loneliness may foster suicidal ideation and attempts in the general population [START_REF] Calati | Suicidal thoughts and behaviors and social isolation: a narrative review of the literature[END_REF][START_REF] Brooks | The psychological impact of quarantine and how to reduce it: rapid review of the evidence[END_REF]. In a recent narrative review of 40 articles, [START_REF] Calati | Suicidal thoughts and behaviors and social isolation: a narrative review of the literature[END_REF] reported that objective social isolation and subjective feelings of loneliness are associated with higher suicidal ideation and behaviors. In the same vein, [START_REF] Brooks | The psychological impact of quarantine and how to reduce it: rapid review of the evidence[END_REF] reported that quarantine and lockdown measures are associated with poorer mental health status in the general population. However, the effects of social isolation observed in previous EVDOs may be different than the effects of the current pandemic. Indeed, technologies, such as videoconferencing, are now more widely available. Moreover, the quarantine measures are applied to the whole population during the COVID-19 pandemic, while they were only applied to vulnerable groups (e.g., older adults, people with poor health conditions) during the 2003 SARS epidemic [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF], which may have been stigmatizing and isolating for those who were forced into quarantine.

Unexpectedly, we found no evidence for an increased risk of deaths by suicide in people with previous psychiatric disorders during EVDOs [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF].

However, this result has to be interpreted with caution as only three studies [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF][START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF] evaluated the effect of previous psychiatric disorders. People with mental disorders are indeed considered as a vulnerable population during the COVID-19 pandemic [START_REF] Chevance | Ensuring mental health care during the SARS-CoV-2 epidemic in France: a narrative review[END_REF][START_REF] Reger | Suicide mortality and coronavirus disease 2019 -A perfect storm?[END_REF][START_REF] Rajkumar | COVID-19 and mental health: A review of the existing literature[END_REF], and may still require preventive interventions during lockdown [START_REF] Chevance | Ensuring mental health care during the SARS-CoV-2 epidemic in France: a narrative review[END_REF][START_REF] Yao | Patients with mental health disorders in the COVID-19 epidemic[END_REF].

Implications for suicide prevention strategies during EVDOs

Our results indicate the need to design adaptive suicide prevention during EVDOs, focusing on their psychosocial impacts. First, our results may give the impression that practitioners should routinely assess for fear of infection during EVDOs to detect people with higher suicide risk. For example, [START_REF] Ahorsu | The Fear of COVID-19 Scale: development and initial validation[END_REF] recently developed and validated the 7-item Fear of COVID-19 Scale in a sample of 717 Iranian participants. However, there is insufficient evidence to support the clinical utility of such screenings to reduce mental health symptoms [START_REF] Gilbody | Should we screen for depression[END_REF][START_REF] Gilbody | Screening and case-finding instruments for depression: a meta-analysis[END_REF][START_REF] Keshavarz | Screening for depression: a systematic review and meta-analysis[END_REF] or prevent suicides (Oyama et al., 2008;[START_REF] Belsher | Prediction Models for Suicide Attempts and Deaths: A Systematic Review and Simulation[END_REF]. Thus, it would be premature to integrate these screenings into clinical practice at this point. Second, as emphasized by [START_REF] Reger | Suicide mortality and coronavirus disease 2019 -A perfect storm?[END_REF], social connection plays a key role in suicide prevention, so that the prevention of loneliness induced by quarantine measures should be included in public health policies during the COVID-19 pandemic. Notably, brief contact interventions, through phone calls or postcards, appear to be a promising strategy to reduce suicide risk by providing social support and promoting distance-based access to mental health care [START_REF] Milner | Mechanisms of brief contact interventions in clinical populations: a systematic review[END_REF]. Third, during the 2003 SARS outbreak, older adults were reported as being particularly vulnerable to suicide [START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF][START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF][START_REF] Yip | The impact of epidemic outbreak: the case of severe acute respiratory syndrome (SARS) and suicide among older adults in Hong Kong[END_REF]. Thus, mitigating the impact of social isolation and of the fear of infection in older adults are two specific objectives that must be properly addressed during the COVID-19 pandemic. However, two recent systematic reviews reported that the literature on suicide prevention in older adults [START_REF] Zeppegno | Psychosocial suicide prevention interventions in the elderly: a mini-review of the literature[END_REF] and in nursing homes [START_REF] Chauliac | Suicide prevention interventions for older people in nursing homes and long-term care facilities: a systematic review[END_REF] is scarce. Psychotherapies for suicide prevention have been tailored for older adults and have been demonstrated to be effective in reducing suicidal behaviors [START_REF] Zeppegno | Psychosocial suicide prevention interventions in the elderly: a mini-review of the literature[END_REF].

Interestingly, telephone helplines providing brief counselling and emotional support have been reported to be effective in preventing suicidal behaviors in older adults in Italy [START_REF] De Leo | Lower suicide rates associated with a Tele-Help/Tele-Check service for the elderly at home[END_REF][START_REF] De Leo | Suicide among the elderly: the long-term impact of a telephone support and assessment intervention in northern Italy[END_REF] and in Hong Kong [START_REF] Chan | Elderly suicide and the 2003 SARS epidemic in Hong Kong[END_REF]. Fourth, regarding the results from [START_REF] Cheung | A revisit on older adults suicides and Severe Acute Respiratory Syndrome (SARS) epidemic in Hong Kong[END_REF] and [START_REF] Keita | Depressive symptoms among survivors of Ebola virus disease in Conakry (Guinea): preliminary results of the PostEboGui cohort[END_REF] on suicidal behaviors in the post-epidemic periods, prevention strategies must be designed in a long-term fashion and also target people infected by the SARS-CoV-2 as they may exhibit high level of post-traumatic, anxiety and depressive symptoms in the aftermath of the infection [START_REF] Duan | Psychological interventions for people affected by the COVID-19 epidemic[END_REF].

Limitations

Our review has several limitations. First, the number of included articles is low and their quality is heterogeneous. This highlights the scarcity of literature on the topic and the urgent need to collect nationwide and worldwide data on the psychological impact of the current COVID-19 pandemic. In agreement with recent editorials (Gunnell et al., 2020;[START_REF] Holmes | Multidisciplinary research priorities for the COVID-19 pandemic: a call for action for mental health science[END_REF], our results stress the need to perform high quality research on suicide risk and prevention in the current pandemic context. Second, the included studies were performed in a small number of countries. Suicidal behaviors are known to be shaped by cultural and social contexts, so the generalizability of our conclusions may be hampered. For example, the suicide rate in older adults in Hong Kong was known to be high compared to other countries at the period preceding the 2003 SARS outbreak [START_REF] Chi | A study of elderly suicides in Hong Kong[END_REF]. Third, only two studies assessed the long term impact of EVDOs on suicidal ideation and behaviors, so that the evidence on the long-term impact of EVDOs remains poorly understood. Thus, our results only weakly inform what the long-term impact of the current COVID-19 pandemic might be on suicidal behaviors. Fourth, the review did not examine other specific high-risk groups than older adults, so that our results fail to inform targeted suicide prevention strategies. Finally, the between-studies heterogeneity was high regarding quality, design, population, and outcomes and may thus limit the relevance of our results.

CONCLUSION

While the literature on the impact of EVDOs on suicidal ideation and behaviors was found to be scarce, the existing literature shows weak evidence for an increased risk of deaths by suicide during viral outbreaks, especially during the peak epidemics. The pathways by which EVDOs and suicide are related remain not entirely understood, but their psychosocial effects may be regarded as the main risk factors. Public health and suicide prevention strategies must target the most vulnerable populations that struggle the most to adapt to EVDOs. (post-epidemic period) compared to the pre-epidemic period (IRR = 0.83, 95% CI 0.70-0.99; p=0.045 in April 2002 compared to 2004).

• Differences in medical profile among the older adult in the pre-SARS, peri-SARS and post-SARS periods: significant impact of the severity of illness (p < 0.001), the level of dependency (p = 0.013) and the fear of being infected (p = 0.021) during the peri-SARS period

  (a) (suicid* OR self-harm OR self-injury OR self-destruct* OR DSH OR self-poison* OR self-mutilat* OR self-inflict*), b) (pandemic* OR epidemic* OR outbreak), and c) (coronavirus OR influenza OR infectious OR infection OR virus OR viral OR MERS-CoV OR SARS OR Ebola OR Zika OR Chikungunya OR H1N1 OR H5N1 OR lockdown OR quarantine).

Figure 1 .

 1 Figure 1. Flow chart diagram of study selection according to the PRISMA guidelines

Table 1 . Characteristics, designs and results of the studies included in the systematic review

 1

	Chan et al.	Hong	2003 SARS Cross-sectional	Population of	NA	Prevalence of	• Increased suicide rates for people	21
	(2006)	Kong (China)	Naturalistic observational study	Hong Kong		deaths by suicide	over 65 (IRR = 1.32, 95% CI 1.11-1.57; p = 0.002 compared to 2002).
			Comparison of suicide rates				• Increased suicide rates for female
			between 2003 and the 17 years preceding the SARS				elders (IRR = 1.42; p= 0.014). • Non-significant increased suicide
			epidemic				rates for male elders (IRR = 1.22;
			Data comes from the Census and Statistics Department of the Hong Kong Government				p = 0.09). • No increase in suicide rates for people under 65 (IRR = 0.97; p = 0.47).
							• Excess in elderly suicide rates in
							April 2003 (peak of the outbreak)
	Cheung et al.	Hong	2003 SARS Cross-sectional	Population of	321	Prevalence of	• Increased suicide rate in older
	(2008)	Kong (China)	Naturalistic observational study	Hong Kong aged over 65 and people		deaths by suicide	adults in 2003 (IRR = 1.18, 95% CI 1.01-1.39 compared to 2004). • Peak of suicide rate in older
			Comparison of suicide rates between 2003, the 10 years epidemic and the year just preceding the SARS	aged over 65 who died by in Hong Kong suicide in 2003			adults during the peak-epidemic in April 2003 • Increased suicide rate in 2004
			after the SARS epidemic
			Comparison of socio-
			demographic, medical and
			psycho-social data of the
			people aged over 65 who
			committed suicide in 2003 in
			Hong Kong
			Data based on Coroner's
			death records

Table 1 . Characteristics, designs and results of the studies included in the systematic review

 1 United Kingdom; 2003 SARS = 2003 Severe Acute Respiratory Syndrome; SA = suicide attempt *The quality of studies was assessed with the 32-item STROBE statement, a score of 1 (presence) or 0 (absence) was coded for each item (total score on 32)

	• No impact of psychiatric problems
	(p = 0.23) or feeling of burden (p
	= 0.45)

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

• Non-significant increase of visits for SA from drug overdose during the peak-epidemic stage: peakepidemic: 3.3 ± 1.8 (2.8 ± 1.5) visits per day vs pre-epidemic: 2.5 ± 1.8 (1.2 ± 1.0) visits per day (p > 0.05). • No increase of attendance for SA from drug overdose in the lateand post-epidemic periods (late epidemic: 2.4 ± 1.5 (2.4 ± 1.4); and post epidemic: 2.3 ± 1.4 (1.4 ± 1.0)


Florian Lahrouch
email: florian.lahrouch@upmc.fr

Ning Guo

Myrtille O J Y Hunault

Pier Lorenzo Solari

Michael Descostes

Martine Gerard
email: martine.gerard@upmc.fr

Uranium retention on iron oxyhydroxides in post-mining environmental conditions

Keywords: uranium, mining wastes, uranium migration, EXAFS spectroscopy, iron oxyhydroxides, environment

Investigating uranium migration mechanisms related to the weathering of waste rocks is essential for developing strategies that can address the potential environmental issues caused by uranium mining. This work is based on environmental samples containing 2 L ferrihydrite, lepidocrocite and goethite collected in the technosols from granitic waste rock piles, mine drainage conduits and mine waters. The results show the important role of iron oxyhydroxide in U immobilization and re-concentration.

Introduction

The environmental fate of granitic waste rocks produced as a result of uranium mining activity is a source of concern for governmental authorities as well as mining companies because the waste rocks represent a potential source of radioactive contamination for both soil and groundwater (OECD-NEA&IAEA, 2018). In general, waste rocks are composed of barren rocks that have U concentrations corresponding to the geological background of the region (10-20 ppm) [START_REF] Cuney | Felsic magmatism and uranium deposits[END_REF][START_REF] Ielsch | Estimation and mapping of uranium content of geological units in France[END_REF] and of low-grade ore that falls below the cut-off point (from 100 to 300 ppm) of economic viability (AREVA-NC, 2007). After extraction, the waste rocks are generally piled up in the vicinity of the mining sites. They also can be used to cover tailings or to backfill open-pits. Through exposure to the elements and the weathering process, the waste rock blocks are transformed into granitic arena (Sequeira [START_REF] Braga | Weathering of granites in a temperate climate (NW Portugal): granitic saprolites and arenization[END_REF] and other associated technosols (IUSS Working Group WRB, 2014; [START_REF] Santini | Assessment of Technosol formation and in situ remediation in capped alkaline tailings[END_REF].

During the arenization process, the primary U phases, coffinite (U IV (SiO4)1-x(OH)4x) and uraninite (U IV O2), are oxidized into soluble uranyl UO2 2+ groups that are known to be mobile (Grenthe et al., 2006). In the technosols, secondary minerals such as phyllosilicates, ferric oxyhydroxides or phosphates control uranium migration through different processes such as sorption or precipitation [START_REF] Jin | Surface complexation modeling of U(VI) adsorption on granite at ambient/elevated temperature: Experimental and XPS study[END_REF][START_REF] Cretaz | Solubility properties of synthetic and natural meta-torbernite[END_REF][START_REF] Lee | Development of a web-based sorption database (KAERI-SDB) and application to the safety assessment of a radioactive waste disposal[END_REF]. Uranyl (UO2 2+ ) forms soluble complexes with a variety of anionic species, including carbonate, phosphate or organic matter, which tend to limit its hydrolysis and increase its mobility [START_REF] Langmuir | Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits[END_REF].

Conversely, sorption on mineral phases such as ferric oxyhydroxides or precipitation of secondary minerals such as uranyl phosphates tend to control the U mobility [START_REF] His | Adsorption of uranyl onto ferric oxyhydroxides: application of the surface complexation site-binding model[END_REF].

Iron mobility is one the most efficient indicators of weathering conditions. A large panel of iron oxyhydroxides are observed in soils and supergene environments [START_REF] Vodyanitskii | Iron Hydroxides in Soils: A Review of Publications[END_REF].

Ferrihydrite (Fh) is a common mineral phase in the environment [START_REF] Jambor | Occurance and Constitution of Natural and Synthetic Ferrihydrite, a Widespread Iron Oxyhydroxide[END_REF] and more generally wherever Fe II oxidation is rapid [START_REF] Schwertmann | Iron Oxides in the Laboratory. Preparation and Characterization. Second, Completely Revised and Extended Edition[END_REF]. A strong leaching of iron associated to organic matter contain favors the precipitation of ferrihydrite in humid well drained systems such as soils, or paleosoils (Gerard et al., 2007;[START_REF] Churchman | Alteration, Formation, and Occurrence of Minerals in Soils[END_REF]. Ferrihydrite has been extensively studied for catalysis applications (Zhao et al., 1994) and use in metallurgy [START_REF] Misawa | The mechanism of formation of iron oxide and oxyhydroxides in aqueous solutions at room temperature[END_REF] and geochemistry especially because of its capacity to sorb minor elements in surface and groundwater systems [START_REF] Kinniburgh | Specific sorption of trace amounts of calcium and strontium by hydrous oxides of iron and aluminum[END_REF][START_REF] Music | Adsorption of trace elements or radionuclides on hydrous iron oxides[END_REF][START_REF] Sajih | Adsorption of radium and barium on goethite and ferrihydrite: A kinetic and surface complexation modelling study[END_REF].

Ferrihydrite is a short-range order mineral that occurs as spherical nanoparticles [START_REF] Michel | The Structure of Ferrihydrite, a Nanocrystalline Material[END_REF], is thermodynamically unstable, and with time converts to stable Fe-oxide as goethite or hematite [START_REF] Carlson | Natural ferrihydrites in surface deposits from Finland and their association with silica[END_REF][START_REF] Schwertmann | From Fe(III) Ions to Ferrihydrite and then to Hematite[END_REF]. However, crystallization inhibitors such as organics, phosphate or silicate species can stabilize the ferrihydrite and retard its transformation into more stable minerals [START_REF] Schwertmann | Iron Oxides in the Laboratory. Preparation and Characterization. Second, Completely Revised and Extended Edition[END_REF].

In post mining environment, the weathering conditions control the release and leaching of heavy metals, lanthanides and actinides related to the ore extraction process. Ferrihydrite which has high sorption capability related to its high specific surface is a first trap for these toxic elements. Studies reported that the ferrihydrite is effective to retain heavy metals such as Cr, As, Se, Cd, Zn and Pb (Waychunas et al.,1993;[START_REF] Manceau | The mechanism of selenite adsorption on goethite and hydrous ferric oxide[END_REF][START_REF] Dyer | Lead sorption onto ferrihydrite 2. Surface complexation modeling[END_REF][START_REF] Dyer | Surface complexation modeling of zinc sorption onto ferrihydrite[END_REF][START_REF] Qian | In-situ stabilization of Pb, Zn, Cu, Cd and Ni in the multi-contaminated sediments with ferrihydrite and apatite composite additives[END_REF][START_REF] Du | Binding of Cd by ferrihydrite organo-mineral composites: implications for Cd mobility and fate in naturaland contaminated environments[END_REF] as well as dissolved uranyl species [START_REF] Ames | Uranium and radium sorption on amorphous ferric oxyhydroxide[END_REF][START_REF] His | Adsorption of uranyl onto ferric oxyhydroxides: application of the surface complexation site-binding model[END_REF]Langmuir, 1985, Waite et al., 1994;[START_REF] Dublet | Partitioning of uranyl between ferrihydrite and humic substances at acidic and circum-neutral pH[END_REF] through the formation of inner-sphere sorption complexes or by co-precipitation. For the long-term performance assessment of nuclear waste repositories, the ferrihydrite ability to immobilize lanthanides, as Lu(III), Ce(III) or Pr(III) and trans-uranium actinides, as Np(IV) or Am(III) were also reported [START_REF] Sakamoto | Redistribution of Neptunium (V) During the Alteration of Ferrihydrite[END_REF][START_REF] Stumpf | Sorption of Am(III) onto 6-line ferrihydrite and its alteration products: investigations by EXAFS[END_REF][START_REF] Riley | The behaviour of the rare earth elements during the precipitation of ferrihydrite from sulphate media[END_REF][START_REF] Finck | Fate of Lu(III) sorbed on 2-line ferrihydrite at pH 5.7 and aged for 12 years at room temperature. I: Insights from ICP-OES, XRD, ESEM, AsFlFFF/ICP-MS and EXAFS spectroscopy[END_REF].

Phosphate ions or organic matter affect the retention behavior of uranyl in oxic geochemical systems, resulting in an increase in uranyl uptake on ferrihydrite [START_REF] Payne | Uranium Adsorption on Ferrihydrite -Effects of Phosphate and Humic Acid[END_REF]. This process is attributed to the strong surface binding of both phosphate and organic matter and the subsequent formation of ternary surface complexes with uranyl during their sorption to ferrihydrite [START_REF] Payne | Uranium Adsorption on Ferrihydrite -Effects of Phosphate and Humic Acid[END_REF]. In the case of phosphate, several studies have not excluded the possibility of precipitation of a uranyl phosphate phase at the oxide surface [START_REF] Dzombak | Surface Complexation Modeling, Hydrous Ferric Oxide[END_REF][START_REF] Payne | Adsorption of Metals by Geomedia, variables Mechanisms, and Model Applications[END_REF][START_REF] Galindo | Mechanisms of uranyl and phosphate (co)sorption: Complexation and precipitation at α-Al2O3 surfaces[END_REF]. The precipitation of the mineral phase resulting from a ternary surface complex formation on the oxide surface is also debated for heavy metals such as Pb or Cd (Weesner and Bleam, 1998;Zhu et al., 2014).

The purpose of this paper is to demonstrate how uranyl phases can be controlled by ferric oxyhydroxides in the post-mining environment. The occurrence of other species associated with uranyl sorption are discussed relative to various post-mining environmental systems and parageneses. Ferric oxyhydroxide-rich samples collected from technosols and colloidal fractions of mine waters were analyzed by a combination of X-ray diffraction (XRD) and elemental analyses to identify the U-bearing phases and by extent X-ray absorption fine structure spectroscopy (EXAFS), which supplies valuable information on U speciation.

Materials and methods

Analytical conditions.

The pH control was carried out with a Metler Toledo equipped with an LE438 pH electrode.

The centrifugation separations were performed at 10000 g for 30 min on a Sigma 2-16P. The milliQ water (18 Ω) were produced by a Millipore Elix ® Advantage UV unity. The Fe(NO3)3.9H2O, KOH, NaOH were purchased from Alfa Aesar. The XRD analyses were achieved using an X'pert Pro Panalytical diffractometer with Fe filtered CoKα radiation (40 kV, 40 mA). All samples were finely grounded in an agate mortar for homogenization to prepare powder samples for XRD and EXAFS characterization. The samples were digested with a mix 1:3 nitric acid (65%)/hydrofluoric acid (40%) at 60°C for 12h. Each digested solution was dried and dissolved into 10 mL of a nitric acid solution (7,4 M) containing boric acid (10g/L). Then aliquot amounts of solution (1 mL) were taken and diluted until reaching 2% before being measured by ICP-OES and mass spectroscopy (Agilent Technologies 8800 ICP-MS-MS Triple Quad and with an Agilent Technologies 5100 ICP-OES SVDV at ALIPP6 Sorbonne University, Paris).

The SEM pictures using back scattering electrons mode (BSE) were recorded on a ZEISS Supra 55 VP (ECCE TERRA, Observatoire des Sciences de l'Univers, Sorbonne University -INSU). The WDS microprobe characterizations were achieved for aluminium, calcium, iron, potassium, magnesium, neodymium, oxygen, phosphorus, sulphur, silica and uranium with CAMECA SX-100 equipped with four WDS and one EDS detectors (CAMPARIS, Sorbonne University).

Synthesis and characterization of the reference (Fh-PO4-U).

2 line Ferrihydrite was prepared by dropwise adding a solution of potassium hydroxide (1M) to 140 ml of Fe(NO3)3.9H2O (0.2 M) until pH 6. The mixture was vigorously stirred while the additions were made for a period of 24 hours. The product was separated by centrifugation, twice washed with milliQ water and heated at 25°C for 3 days. The brown powder obtained was analysed by XRD and the two largest signals centred on 2.5 Å and 1.5 Å, characteristic of 2L ferrihydrite, were observed (ESI_Fig 6).

The reference (Fh-PO4-U) was prepared by dropwise adding 630 µL of a uranyl phosphate solution (4.9 mM, pH1) to 250 mg of synthetized ferrihydrite which was beforehand dispersed in 5mL of milliQ water using an ultrasonic bath. The pH was controlled in continue to stay between 3.5 and 5 by the addition of sodium hydroxide solution (0.05 M).

The solution of uranyl phosphate was prepared by mixing a solution of uranyl nitrate (0.01 M) with a solution of phosphoric acid (0.3 M). During each addition and then for 12 hours the mixture was stirred vigorously.

Fh-PO4-U were recovered by centrifugation, washed with milliQ water and heated at 25°C for 3 days. Elemental analyses: (Fh-PO4-U) U=1850 ppm; Fe= 46.7 wt%; P= 1.2 wt%.

(ESI_Table 1).

Sampling

Five samples (Table 1), all coming from former U mining sites, containing iron oxyhydroxide were selected for determination of U speciation via EXAFS. Three samples were collected in technosols from granitic waste rock piles located in Fanay, Limousin France [START_REF] Boekhout | Uranium migration and retention during weathering of granitic waste rock piles[END_REF][START_REF] Kanzari | Migration de l'uranium, en conditions d'altération météorique, dans les verses à stériles granitiques[END_REF], and two samples with ferrihydrite were taken from mine waters on the granitic waste rock pile of Hyverneresse, Limousin, France [START_REF] Kanzari | Impact of incipient weathering on uranium migration in granitic waste rock piles from former U mines (Limousin, France)[END_REF] and from a mine drainage conduit of the Bois Noir Limouzat mining site, Loire, France, in the granite of the "Montagne Bourbonnaise" district [START_REF] Husson | Environmental geochemistry and bioaccumulation/bioavailability of uranium in a post-mining context e The Bois-Noirs Limouzat mine (France)[END_REF]. These samples were characterized with XRD, ICP-OES/MS, SEM/EDS, and WDS.

The granite paragenese consists of quartz, albite, orthoclase, biotite and muscovite. Uraninite and coffinite, associated with hydrothermal episodes, are the primary U ore minerals. 1) and diffractograms (ESI Fig. 1,2,3,4 and 5) are presented in the ESI. FAN0508, FAN0507 and FAN0502C were collected in a trench dug in the technosol at the base of the waste rock pile located at the Fanay mining site [START_REF] Kanzari | Migration de l'uranium, en conditions d'altération météorique, dans les verses à stériles granitiques[END_REF]. The pH of these three samples is slightly acidic, between 4 and 5.

The chemical composition table (ESI Table

FAN0508 was sampled in the upper clay liner (2 cm thick) of an alluvial soil horizon 20 cm below the surficial waste rock widespread deposit. In this liner, uranium is highly concentrated (13600 ppm). Bulk analyses for Fe indicate 14.6 wt% and P 0.8 wt% (ESI_Table 1). The XRD analysis achieved on the fine fraction (<2µm) shows the two characteristic bulges of the 2 line ferrihydrite at 2.5 Å and 1.5 Å, as well as smectite, kaolinite, quartz, feldspar and mica peaks.

FAN0507 localized just below the FAN0508 liner, was collected in the soil horizon, between 50 and 70 cm deep below the surficial waste rocks. This silty clayey horizon chemical composition is 400 ppm of U, 2.6 wt% of Fe and 0.1 wt% of P. Phosphate submicrometric minerals were observed by SEM/EDS. The 2.69 Å peak suggest goethite occurrence. Chlorite, vermiculite, kaolinite, biotite, quartz, feldspar and mica compose the main parageneses.

FAN0502C was collected 1m below the surficial waste blocks in an orange brown discontinue oxidation front. Chemical bulk composition is 1400 ppm of U, 24.3 wt% of Fe and 0.1 wt% of P in this sample. The parageneses of this sample is mainly kaolinite, muscovite, quartz, feldspar and mica. XRD data indicate a mixture of lepidocrocite and goethite, with the following peaks occurrence: at 6.23, 1.93 and 1,73 Å for lepidocrocite and 2.69 Å for goethite. It can be noted that the peaks of 3,29 Å and 2,47 Å of the lepidocrocite and the peak of 4.13 Å of the goethite are overlapped by the quartz signals.

HYV0105 was sampled in red deposits located in mine waters on the granitic waste rock pile of Hyverneresse, Limousin, France. Chemical composition is 2100 ppm of U, 35.2 wt% of Fe and 1.4 wt% of P. The XRD data shows 2 lines ferrihydrite, quartz, feldspar and mica [START_REF] Kanzari | Impact of incipient weathering on uranium migration in granitic waste rock piles from former U mines (Limousin, France)[END_REF].

BNL canal 2B was collected in the upper sediment layer formed in the mine drainage conduit of Bois Noir Limouzat mine, Loire, France, at 40m from the underground mine outlet. The pH was measured to be 6.5. Chemical composition is 2100 ppm of U, 39.1 wt% of Fe and 0.5 wt% of P. We can also note the concentration of carbon, equal to 3.6 wt %, which indicates the presence of organic matter or carbonate. The XRD data show ferrihydrite, quartz feldspar and mica [START_REF] Husson | Environmental geochemistry and bioaccumulation/bioavailability of uranium in a post-mining context e The Bois-Noirs Limouzat mine (France)[END_REF].

Table 1: Description of samples collected from different geological environments in the mining sites.

Petrographic thin section

A petrographic thin section of FAN0508 sample was prepared by impregnation of an aggregate of the H0 horizon in an epoxy resin of 30 μm thickness which is glued on a glass substrate of 25 mm x 29 mm. The thin section was mapped by optical microscopy (Fig 2b) and by scanning electronic microscopy using BSE mode (Fig 3a

EXAFS measurements and processing

EXAFS experiments at the U LIII edge were performed on the MARS beamline of the SOLEIL synchrotron facility. The MARS beamline is dedicated to investigation of radioactive materials in the hard X-ray range. Because of the low concentration of the samples, EXAFS measurements were performed in fluorescence mode using a 13-element high purity germanium detector (ORTEC). The powder samples were prepared as pellets with a diameter equal to 7 mm and using a specifically designed 12-position sample holder. The petrographic thin section was mapped beforehand by an X-ray fluorescence map (XRF) at the U LIII edge and subsequently characterized by EXAFS using a 300 x 250 µm 2 beam. All samples were cooled near 115 K using a LN2 cryostat. The optics of the beamline essentially consist of a water-cooled double-crystal monochromator (FMB Oxford), which is applied for selection of the incident energy of the X-ray beam and for horizontal focalization, and two large water-cooled reflecting mirrors (IRELEC/SESO) that are used in high-energy rejection harmonic and vertical collimation and focalization. In this case, the monochromator was set with Si (220) crystals and mirrors with Pt strips. Energy calibration was performed at the Y K edge at 17038 eV. Data processing was conducted using the ATHENA code [START_REF] Ravel | ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT[END_REF]. The Eo energy was identified at the maximum of the absorption edge for data fitting.

EXAFS data fitting

Fourier transformation (FT) in k 2 was performed between 3 and 12 Å -1 with Hanning windows using the ARTEMIS code [START_REF] Ravel | ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT[END_REF]. Only one global amplitude factor S0 2 and one energy threshold correction factor ΔE0 were used in all paths. Phases and amplitudes were calculated using the FEFF6 simulation code [START_REF] Rehr | Parameter-free calculations of X-ray spectra with FEFF9[END_REF] included in [START_REF] Basile | Structural characterization of environmentally relevant ternary uranyl citrate complexes present in aqueous solutions and solid state materials[END_REF]. The total coordination number was fixed to 5+2, which is a usual coordinate for uranyl. Single scattering paths were considered for the oxo oxygens (Oax), equatorial oxygens, phosphorus, carbon or iron atoms according to the sample. Triple Oax-U-Oax scattering paths were also considered and linked to the corresponding single paths. The addition of a single scattering path modeling the apical oxygen atom significantly improved the fit. 13

Table 2: EXAFS best-fit parameters for the HYV0105, BNL canal 2B, Fh-PO4-U, FAN0508, FAN0507, FAN0502C and FAN0508 thin section. CNs were fixed to 2 for the axial and to 5

for the equatorial oxygen atoms (numbers in italics). The numbers in parentheses are the estimated uncertainties, σ 2 is the Debye-Waller factor of the scattering path, S0 2 is the global amplitude factor, e0 is the energy threshold, Rfactor is the quality factor of the fit in percent, and Q is the reduced χr 2 factor of the fit.

Results

Iron oxyhydroxides and uranyl sorption 14

The experimental EXAFS spectra of the FAN0508, FAN0507, FAN0502C, Fh-PO4-U, BNL canal 2B, and HYV0105 samples at the U LIII edge are shown in figure 1a, and the corresponding FT is presented in figure 1b. For each sample, the modulus of the FT exhibits the characteristic short-range axial shell of the two oxo bonds of UO2 2+ for the first coordination sphere, of which the equatorial shell is also well resolved and indicates a single contribution. A second coordination sphere is visible between R + Φ = 2.2-3.2 A ̊ with a weaker signal. The best fit metrical parameters are displayed in Table 2. For all samples, the two axial oxygen atoms are located between 1.78 and 1.80 A ̊. In the equatorial uranyl plane, the U-Oeq distances are found between 2.32 and 2.38 A ̊, in agreement with the number of oxygen atoms fixed to 5 [START_REF] Burns | U 6+ minerals and inorganic compounds: insights into an expanded structural hierarchy of crystal structures[END_REF]. The Debye-Waller factor associated with the contribution of the equatorial oxygen atoms is rather high (between σ 2 =0.0096 A ̊2 and σ 2 =0.0127 A ̊2) for pure sorption of the uranyl at the ferrihydrite surface. These high values of σ 2 indicate high disorder of the equatorial oxygen atoms, suggesting that uranium is coordinated with different small molecules such as H2O, phosphates or carbonates and organic matter. The different types of equatorial oxygen atoms were not distinguished in the fits to limit the number of fitting parameters. A strong contribution near 3.56 A ̊ is systematically observed, corresponding to Oax-U-Oax multiple scattering.

Another contribution between 2.71 and 2.74 A ̊ highly enhances the fit quality. We attributed this last contribution to surface oxygen atoms from iron oxides [START_REF] Ulrich | Molecular characterization of uranium (VI) sorption complexes on iron(III)-rich acid mine water colloids[END_REF]. This latter interpretation is supported by the XRD results. Ferrihydrite is identified in HYV0105, FAN0508 and BNL canal 2B; goethite in FAN0507; and a mix of lepidocrocite/goethite in FAN0502C (ESI Fig. 1, 2, 3, 4 and 4).

In HYV0105, FAN0508 and FAN0502C, the second coordination sphere of uranyl is composed of phosphorus atoms at 3.63(2), 3.65(2) and 3.69(4) A ̊, respectively. The synthetic Fh-PO4-U sample, which gives a reference of uranyl phosphate sorbed on ferrihydrite, also exhibits the U…P contribution at 3.65(2) A ̊, which is consistent with the distance described in the literature for monodentate uranyl phosphate [START_REF] Vazquez | Interactions of uranium with polyphosphate[END_REF][START_REF] Kelly | Chapter 14 -Uranium Chemistry in Soils and Sediments[END_REF]. A weak contribution of iron atoms at 3.32(2) A ̊ occurs for the reference Fh-PO4-U, which is not obvious in the other samples.

Concurrently, the results of ICP-OES and MS chemical analyses for U range from 2100 to 13000 ppm in the ferrihydrite rich samples and from 0.78 to 1.42 wt% for P (ESI Table 1).

The high cation exchange capacity and specific surface area enable ferrihydrite to sorb a wide range of compounds (Waychunas et al.,1993;[START_REF] Manceau | The mechanism of selenite adsorption on goethite and hydrous ferric oxide[END_REF][START_REF] Payne | Uranium retention by weathered schists -the role of iron minerals[END_REF][START_REF] Schwertmann | Iron Oxides in the Laboratory. Preparation and Characterization. Second, Completely Revised and Extended Edition[END_REF][START_REF] Dyer | Lead sorption onto ferrihydrite 2. Surface complexation modeling[END_REF][START_REF] Dyer | Surface complexation modeling of zinc sorption onto ferrihydrite[END_REF][START_REF] Qian | In-situ stabilization of Pb, Zn, Cu, Cd and Ni in the multi-contaminated sediments with ferrihydrite and apatite composite additives[END_REF][START_REF] Du | Binding of Cd by ferrihydrite organo-mineral composites: implications for Cd mobility and fate in naturaland contaminated environments[END_REF]. Lepidocrocite and goethite have a reduced sorption capacity compared with ferrihydrite, which is consistent with the lower U and P concentrations observed in FAN0502C.

The second coordination shell of U in BNL canal 2B exhibits a carbon contribution at 3.27(4)

A ̊. This distance is similar to the congested monodentate carboxylic acid complexation described in the literature [START_REF] Lahrouch | A Combined Spectroscopic/Molecular Dynamic Study for Investigating a Methyl-Carboxylated PEI as a Potential Uranium Decorporation Agent[END_REF][START_REF] Dublet | Partitioning of uranyl between ferrihydrite and humic substances at acidic and circum-neutral pH[END_REF] and indicates organic carbon occurrence in the uranyl coordination shell. This sample is a component of the upper sediment of the mining conduit, composed of 2 L ferrihydrite, with 2100 ppm of uranium and 3.6 wt% of organic carbon (ESI Table 1).

In the soil horizon below the FAN0508 ferrihydrite rich liner, the second coordination shell of U in FAN0507 is composed of iron and phosphorus contributions at 3.41(2) A ̊ and 3.54(3) A ̊, respectively. Compared with the synthetized reference Fh-PO4-U, the U…P distance is shorter and that of U…Fe is larger, suggesting another iron oxyhydroxide occurrence similar to goethite/hematite (ESI Fig. 1). Besides, Moyes et al. described the U…Fe distance equal to 3.47 A ̊ in case of uranyl sorption on goethite [START_REF] Moyes | Uranium Uptake from Aqueous Solution by Interaction with Goethite, Lepidocrocite, Muscovite, and Mackinawite: An X-ray Absorption Spectroscopy Study[END_REF]. The U and P concentrations below the ferrihydrite liner are much lower at 380 ppm for U and 0.1 wt% for P (ESI Table 1).

In situ observations of ternary surface complexes

The XRF map recorded at the U LIII edge and the petrographic thin section optical microscopy image of FAN0508, the most U-concentrated sample, are compared in figures 2a and b. The highest U concentrations occur in the orange ferrihydrite liner visible on the right side of the section.

Submicrometric mineralogical and chemical characterizations, SEM, and WDS mapping were performed (Fig. 3a,b). On the BSE image (Fig. 3a), root cell relics are mixed within the ferrihydrite liner. The liner is composed of approximately 100 µm ferrihydrite concretions containing cell relics and residual primary minerals surrounded by a poorly mineralized cell relic network. This cell relic network appears to be Fe-enriched up to 10 wt% on the WDS maps (Fig. 3b). The WDS maps presented in Fig. 3b highlight the correlation of iron, phosphorus and uranium. The WDS maps of the ferrihydrite concretion range from 2 to 4 wt% for P and from 2.5 and 11 wt% for U (the map was filtered to 6 for a higher image accuracy). The spatial resolution of the WDS microprobe is equal to 2 µm 3 . Chemical composition analysis was achieved on 12000 pixels located on a ferrihydrite concretion identified by a black circle (Fig. 3a). The distribution of the concentrations of Fe, P and U was extracted from the regions of interest (ROI's) of the WDS chemicals maps and are reported in the ESI Figure 7, 8 and 9. Preferential concentrations are observed for U of approximately 9.25, 7.50, 5.60, 3.75 and 1.80 wt%. Approximately 7000 probed points did not contain uranium. The graphical distribution of the P and Fe concentration follows a Gaussian distribution. The average measured concentrations are equal to 2 wt% for phosphorus and 1 wt% for uranium. Rare pixels can reach 11 wt% of U and present a U/P ratio greater than 7.68. This U/P ratio is also found for the crystallized uranyl phosphate minerals such as autunite, meta-autunite, torbernite, meta-torbernite, according to the mineral database (http://webmineral.com) and corresponds to a 1:1 stoichiometry (U/P).

EXAFS characterization was achieved at the U LIII edge using a beam size equal to 300 (H) x 250 (V) µm 2 in the U-rich liner area located at the bottom of the thin section (Fig. 2a). The merge of the recorded EXAFS spectra and the corresponding FT are shown in figures 1a and b. The coordination shell of uranyl is similar to that of the FAN0508 powder sample. The oxygen atom numbers were fixed to 2 for the axial and fixed to 5 for the equatorial atoms.

The U-O distances corresponding to the first coordination shell of the uranium are equal to 1.79(1) Å for the axial and 2.35(2) Å for the equatorial oxygen atoms. The second coordination shell is composed of apical oxygen atoms from the ferrihydrite surface at 2.73(2)

Å and phosphorus atoms at 3.65(6) Å from monodente phosphate groups (Table 2). A strong Oax-U-Oax multiple scattering contribution at 3.56 A ̊ is also required to fit this signal. Other EXAFS data recorded along the ferrihydrite liner on the same thin section are equivalent.

Together, the EXAFS results confirm the presence of U as phosphate complexes sorbed on ferrihydrite. This apparent homogeneity is related to the probe spatial resolution and suggests that the ferrihydrite is the dominant mineral phase controlling the U mobility. the black square marks the SEM/BSE map (Fig. 3).

Discussion

U speciation in the post-mining environment EXAFS spectroscopy combined with mineralogy and geochemistry characterizations is a powerful tool for investigating uranium speciation and associated mineral phases in natural environmental samples. Specific sampling of three horizons in a technosol (FAN0508, FAN0507, FAN0502C) and two ferrihydrite rich samples (HYV0105, BNL canal 2B) from mining drainage waters was performed to investigate the interactions between iron oxyhydroxide minerals and uranium in waste rock piles of former U mines. These samples 20 were chosen because of their high U concentration (10 to 1000 times the typical value for this geological background). For all of these samples, the oxidized form of uranium was identified by EXAFS, indicating re-concentration of soluble uranyl at the molecular scale.

EXAFS results of this study highlight the U immobilization process by ferrihydrite neoformation. The single scattering contribution near 2.73 Å is required for the best fit to the EXAFS signals of BNL canal 2B, HYV0105 and FAN0508. This contribution was described in the literature as U-binding environments occurring at the surface of iron oxyhydroxide phases [START_REF] Ulrich | Molecular characterization of uranium (VI) sorption complexes on iron(III)-rich acid mine water colloids[END_REF][START_REF] Dublet | Partitioning of uranyl between ferrihydrite and humic substances at acidic and circum-neutral pH[END_REF]. This contribution occurs as well in the fit of the reference Fh-PO4-U, which simulates the sorption of uranyl phosphate complexes on the ferrihydrite. The EXAFS signals of the three samples and the reference are similar to that of the same uranyl coordination shell composed of phosphorus atoms at 3.65 Å. Additionally, in the reference, the iron contribution at 3.32 Å corresponds to a bidentate mononuclear innersphere sorption complex. This contribution is reported in the literature at distances of 3. 33-3.42 Å (Waite et al., 1994).

Monodentate uranyl phosphate complexes were identified by EXAFS spectroscopy in the ferrihydrite liner of the upper horizon of the technosol (FAN0508) and mineral neoformations in the mining runoff waters (HYV0105), which is consistent with the chemical data. No X-ray diffraction signals related to uranyl phosphates were observed, suggesting that these complexes are essentially sorbed on ferrihydrite [START_REF] Tayal | Determination of the speciation of U in granitic waste rock piles from Limousin France, by X-ray Absorption Fine Structure spectroscopy[END_REF]. In the surficial mining conduit drainage water sediment (BNL canal 2B), the second coordination shell of uranyl is composed of carbon atoms at 3.27 Å. This U…C distance has been described in the literature for congested carboxylic acids [START_REF] Lahrouch | A Combined Spectroscopic/Molecular Dynamic Study for Investigating a Methyl-Carboxylated PEI as a Potential Uranium Decorporation Agent[END_REF][START_REF] Dublet | Partitioning of uranyl between ferrihydrite and humic substances at acidic and circum-neutral pH[END_REF]. According to the retention time of the sedimentary deposits and organic carbon concentration (ESI Table 1), organic matter is also involved in the uranyl complexation, although the U…C distance value must be considered with care because of the strong Oax-U-Oax multiple scattering extra features.

In the surficial mining waters (HYV0105 and BNL canal 2B), 2 L ferrihydrite is the dominant secondary mineral phase with a high cation sorption capacity. In both cases, ferrihydrite controls the uranyl sorption, but different processes are identified by EXAFS leading to the formation of ternary surface complexes. Uranyl phosphate complexes are sorbed on ferrihydrite for HYV0105. For BNL canal 2B, organic matter promotes the complexation of uranyl, either with direct sorption or as uranyl OM complexes sorbed on ferrihydrite. Both phosphates and organic matter have strong surface binding that allows the subsequent formation of ternary surface complexes. These complexes enhance the uranium sorption capacity of ferrihydrite [START_REF] Payne | Uranium Adsorption on Ferrihydrite -Effects of Phosphate and Humic Acid[END_REF]. The ferrihydrite precipitation in the surficial mining conduit or pools leads to high uranyl re-concentrations (> 2000 ppm).

In the upper technosol horizon, the 2 L ferrihydrite-rich liner FAN0508 is mixed with small amounts of smectite and kaolinite, which might compete for uranyl sorption (ESI Fig. 1).

EXAFS spectroscopy allowed the identification of uranyl phosphate complexes sorbed on ferrihydrite in this soil liner (FAN0508), with a longer retention time for U and a higher U concentration compared with the mining water systems (HYV0105 and BNL canal 2B).

Petrographic thin sections preserve the features and distribution pattern of the soil and allow in situ characterizations. WDS chemical maps with high spatial resolutions on the ferrihydrite liner (Fig. 3b) identified U-rich zones from 2 to 6 wt%. U and P are correlated and localized in the ferrihydrite concretions (Fig. 3a-b). EXAFS data with a beam of 300 x 250 µm 2 show evidence of the dominant control of ferrihydrite on the U sorption (presence of the contribution at 2.73 Å). The concretions trap detrital primary minerals and root cell relics.

These concretions are associated in the soil horizon with root networks and cell vegetal relics.

The Fe and P geochemical signature of the relics observed by WDS in the cell mat (Fig. 3b) suggests thin ferrihydrite coatings on the cells and might be related to the primary ferritin occurrence of biological material [START_REF] Schwertmann | Iron Oxides in the Laboratory. Preparation and Characterization. Second, Completely Revised and Extended Edition[END_REF]. The roots in the liner at the scale of the soil horizon act as a natural barrier supporting the ferrihydrite concretion formations. In addition to the weathering of the granitic waste rocks, degradation of biological material is known to be another source of phosphorus enrichment [START_REF] Singh | Molecular-Scale Structure of Uranium(VI) Immobilized with Goethite and Phosphate[END_REF].

In the ferrihydrite concretions, the heterogeneous U distribution (ESI Fig. 7, 8 and 9) compared with the P and Fe Gaussian-shaped distribution rates suggests preferential sorption or precipitation sites on ferrihydrite. Thereby, 0.05% of the probed points reach 11 wt% U, and half of them have a U/P ratio greater than 7.68 (1:1 U/P stoichiometry), characteristic of uranyl phosphate neoformation such as autunite on the ferrihydrite surface. Goethite occurrences in the soil horizon (FAN0507) below the ferrihydrite liner are identified by XRD.

The U…Fe distance obtained by EXAFS is coherent with U sorption on the goethite surface [START_REF] Moyes | Uranium Uptake from Aqueous Solution by Interaction with Goethite, Lepidocrocite, Muscovite, and Mackinawite: An X-ray Absorption Spectroscopy Study[END_REF][START_REF] Singh | Molecular-Scale Structure of Uranium(VI) Immobilized with Goethite and Phosphate[END_REF], but the U incorporation in the iron oxyhydroxyde structure is difficult to exclude. [START_REF] Payne | Uranium retention by weathered schists -the role of iron minerals[END_REF][START_REF] Ohnuki | Change in sorption characteristics of uranium during crystallization of amorphous iron minerals[END_REF] reported the irreversible incorporation of U in hematite and/or goethite when U is adsorbed onto the precursor ferrihydrite phase. Additionally, the presence of phosphorus atoms in the second coordination shell of uranyl suggests the implication of phosphate groups in the U immobilization process. The relatively shorter U…P distance might signify the neoformation of uranyl phosphate phase as autunite. However, the formation of a uranyl ternary surface complex with phosphate groups on goethite cannot be excluded.

Despite relatively low occurrence in the soil horizon of goethite compared with ferrihydrite occurrence in the upper liner, the U trap efficiency is relevant in this homogenous soil horizon due to the U concentration with a mean U value of 400 ppm. Goethite is thermodynamically more stable than ferrihydrite in aerobic conditions. Below the upper ferrihydrite liner, goethite acts as a secondary trap for U immobilization. Another mineral phase observed in a highly weathered granitic block relic (FAN0502C) is another iron-rich trap for U re-concentration.

The occurrence of lepidocrocite in such a case is controlled by crystallization inhibitors such as uranyl phosphates, which decrease the slow kinetic transformation to goethite [START_REF] Jambor | Occurance and Constitution of Natural and Synthetic Ferrihydrite, a Widespread Iron Oxyhydroxide[END_REF].

Conclusion

The multi-scale approach using EXAFS spectroscopy combined with mineralogical and geochemical characterizations highlights the major role of the iron oxyhydroxides on the uranium mobility in the post-mining environment.

Two lines ferrihydrite was identified as an efficient natural uranyl trap for uranium in the surficial mining conduits or pools as well as in the upper liner of the technosol below the waste rocks piles. The uranium concentration in the ferrihydrite rich clay liner of the technosols is five time the concentration of the ferrihydrite rich water sediments related to the longer residence time of ferrihydrite in the soil.

In situ observations of the U-rich ferrihydrite liner in the technosol show that the root networks and cell vegetal relics support the ferrihydrite growth. In this study, the uranyl sorption on the ferrihydrite surface is associated to the formation of ternary surface complexes with phosphates or organic matters according to the uranium speciation.

According to the WDS microprobe, the uranium concentration on the ferrihydrite concretions is heterogeneous, with U-rich zones exceeding 11wt% but always related to phosphorus occurrence. The U/P ratio > 1:1 stoichiometry suggests local concentration of uranyl phosphates with the possible formation of submicrometric phases in agreement with the uranyl phosphate ternary surface complexes identified by EXAFS.

In the technosols, goethite and lepidocrocite are identified as secondary uranyl traps.

Similarly, to ferrihydrite, the lepidocrocite EXAFS data suggest a surface sorption of uranyl associated to the formation of ternary complexes with phosphate. Goethite is thermodynamically more stable than ferrihydrite and could be a long-term uranyl retention phase, especially if the uranyl is incorporated in the iron oxyhydroxide structure. Such iron oxyhydroxide paragenese suggests a time control of the uranium mobility in the post-mining environment. In oxidizing conditions and even more in strong hydrolyzing environments, ferrihydrite is the most efficient tool for U stabilization as well other anthropic hazardous elements.

Figure 1 :

 1 Figure 1:a) EXAFS spectra of FAN0508, FAN0508 thin section, FAN0507, FAN0502C,

Figure 2 :

 2 Figure 2: a) XRF map of FAN0508 petrographic thin section recorded at the U LIII edge. The

Figure 3 :

 3 Figure 3: a) Back-scattering electron map of a portion of the FAN0508 petrographic thin

  ). Then microprobe analyses were achieved on the ferrihydrite liner (Fig3b).

	Samples	description	U concentration
	FAN0508	2L ferrihydrite enriched clay liner, 20 cm below the surficial waste rocks	13600 ppm
	FAN0507	Silty clayey horizon with goethite occurrence	400 ppm
	FAN0502C	Highly altered granitic block with lepidocrocite and goethite occurrences	1400 ppm
	HYV0105	2L ferrihydrite from colloidal fraction of mine water pools	2100 ppm
	BNL canal 2B	2L ferrihydrite from the upper sediment of a mining drainage conduit	2100 ppm
			10

Acknowledgements

The authors acknowledge the SOLEIL Synchrotron Facility for use of radiation facilities. The authors are also grateful to Dr. S. Savoye (CEA) for assistance and expertise in the U sorption process.

The authors also sincerely thank Omar Boudouma (Plateforme MEB-Sorbonne Université) for acquisition of SEM images and Michel Fialin (CAMPARIS, IPGP, Sorbonne Universite ) for wavelength-dispersive spectroscopy (WDS) measurements.

The authors thank ORANO Mining/AMF staff for their access to the sites and archives documents. This work was supported by ORANO Mining, R & D Department.

Conflicts of interest

There are no conflicts to declare.