Silver : sources, transfer and bioaccumulation : case of the Gironde fluvio-estuarine system

Les rejets d’argent (Ag) dans l’environnement liés à l’exploitation minière aux diverses applications industrielles (e.g. bijouterie, médecine, photographie, électronique et plus récemment les nanotechnologies) font de Ag un polluant historique et émergent, dont les transferts et les effets dans les milieux aquatiques sont largement sous-documentés. Ce travail présente un premier bilan des sources, du transfert et de la bioaccumulation de Ag dans le système fluvio-estuarien de la Gironde. Le continuum Lot-Garonne-Gironde, connu pour une pollution polymétallique (e.g. Cd, Zn) provenant du bassin de Decazeville, est un système modèle pour l’étude des transferts métalliques du continent à l’océan. Les enregistrements des signaux historiques (~50 ans) de Ag dans les sédiments du Lot en amont (Ag : 0,3 mg/kg) et en aval (Ag : jusqu’à 7 mg/kg) du bassin de Decazeville sont similaires à ceux de Cd, indiquant des sources et des processus de transport/dépôt communs liés à l’histoire minière et industrielle jusqu’en 1986. Le lessivage et l’érosion actuels des terrils provoquent localement des concentrations en Ag particulaire (AgP : 260 mg/kg) et dissous (AgD : 1260 ng/l) dans la rivière Riou-Mort qui sont 2 à 3 ordres de grandeur supérieures aux valeurs typiques. Malgré ces fortes concentrations, la contribution du Riou-Mort aux flux de Ag de la Garonne (AgD : 0,008 à 0,041 t/an ; AgP : 0,306 à 2,44 t/an ; 1999-2009) reste faible (AgP : <11% ; AgD : <6%). La Garonne transporte l’essentiel (63-83%) des apports en Ag à l’estuaire principalement sous forme particulaire (96±2%). La détermination du bruit de fond géochimique régional (AgP/ThP=0,026) a permis d’évaluer (i) la contribution naturelle (20% à 65%) aux flux totaux en AgP et (ii) les flux anthropiques spécifiques de AgP (15±10 g/km²/an et 0,24±0,16 g/hab/an) à l’échelle du bassin versant de la Garonne (La Réole). Dans l’estuaire salin, la désorption par les ions chlorures libère ~60% de AgP vers la colonne d’eau (addition), provoquant des concentrations maximales en AgD (6-8 ng/l) à salinité 15-25. La fraction en Ag désorbé correspond à la fraction potentiellement biodisponible ou réactive (i.e. extractible par HCl 1 M). Ainsi, les premières estimations des flux nets indiquent que l’export annuel de Ag vers le domaine côtier est à 50-80% lié à la phase dissoute (0,64 à 0,89 t/an en 2008 et 0,56 à 0,77 t/an en 2009). Bien que plus biodisponible sous forme ionique Ag+ (dominante en eau douce), l’accumulation de Ag dans les organismes estuariens (huîtres, crevettes et anguilles) reflète la pression d’exposition supérieure en eau saumâtre. L’exposition in situ d’anguilles européennes, espèce recommandée pour la biosurveillance du milieu dans le cadre de la Directive Cadre sur l’Eau, dans des cages à différents sites clé de l’estuaire pendant 3 mois, a mis en évidence les voies directes et trophiques de la contamination en Ag à des niveaux de contamination environnementaux. L’enregistrement historique de la contamination en Ag des huîtres de la Gironde (1979-2007, RNO, Ifremer) indique que le bassin de Decazeville a été la source majoritaire en Ag jusqu’en ~1988. Cependant, l’accumulation maximale de Ag dans ces bivalves après 1993 (de ~40 à plus de 100 mg/kg, poids sec) révèle une contribution croissante de sources additionnelles et contemporaines en Ag comme la photographie, l’ensemencement des nuages (30 à 63 kg/an) ou encore les rejets des eaux usées urbaines de Toulouse et de Bordeaux (42 et 57 kg/an). Ce travail constitue une base nécessaire à l’étude des rejets du cycle de Ag (y compris les nanoparticules) dans le milieu aquatique (quantification, transfert et toxicité) et des risques associés.Silver (Ag) emissions into the environment from former mining activities and various industrial applications (e.g. jewellery, medicine, photography, electronic products and more recently nanotechnology) make Ag both a historic and an emergent pollutant for which information on its transfer and toxicity in aquatic system are scarce. This work provides a first assessment of Ag sources, transfer and bioaccumulation in the Gironde fluvial-estuarine system. The Lot-Garonne-Gironde River continuum, known for its polymetallic pollution (e.g. Cd, Zn) derived from the Decazeville basin, is a model system for studies on metal transfer from watersheds to the ocean. The relationship between historical records (~50 years) of Ag concentrations in sediment cores from the Lot River, upstream (Ag: 0.3 mg/kg) and downstream (Ag: up to 7 mg/kg) of the Decazeville basin and those of Cd constitutes evidence of a common source and transport/settlement processes due to industrial activities until 1986. High particulate Ag (AgP: 260 mg/kg) and dissolved Ag (AgD: 1,260 ng/l) concentrations in the Riou-Mort River were attributed to current leaching and erosion of slag heaps by rainwater. Those concentrations were 2 to 3 orders of magnitude greater than typical values in the Gironde watershed. However, the Riou-Mort River contribution to the Garonne River Ag fluxes (AgD: 0.008-0.041 t/a; AgP: 0.306-2.44 t/an; 1999-2009) remained low (AgP: <11%; AgD: <6%). The Garonne River provided the quasi totality (63-83%) of Ag inputs to the estuary, mainly in its particulate form (96±2%). The regional geochemical background (AgP/ThP=0.026) was useful to estimate (i) the natural contribution (20-65%) to total AgP fluxes and (ii) the anthropogenic specific fluxes of AgP (15±10 g/km²/a and 0.24±0.16 g/hab/a) in the Garonne watershed (La Réole). In the estuarine salinity, chloro-complexation desorbed ~60% of AgP, causing maximalum AgD concentrations (6-8 ng/l) at salinity 15-25 (addition to the dissolved phase). This quantity was similar to the potentially bioavailable or reactive fraction (i.e. extracted by HCl 1 M). The first estimations of net fluxes suggested that 50-80% of the Ag annual export to the coast occurred in the dissolved phase (0.64-0.89 t/a in 2008 and 0.56-0.77 t/a in 2009). Even if the ionic form Ag+ (the main form in freshwater) is considered as the most bioavailable form, Ag accumulation in estuarine organisms (oysters, shrimps and eels) reflected the higher exposition pressure in brackish water. In-situ caging of European Eels (recommended species for the biosurvey of aquatic systems; European Water Framework Directive) in key sites of the Gironde Estuary during 3 months, highlighted the direct and trophic pathways of Ag contamination at the environmental level. The historical record of Ag contamination of the Gironde Estuary oysters (1979-2007, French Mussel Watch, RNO) indicated that the Decazeville basin was a major Ag source until ~1988. However, the maximum Ag accumulation in oysters after 1993 (from ~40 to more than 100 mg/kg, dry weight) suggested an increasing contribution of additional and contemporary Ag sources like photography, cloud seeding (30-63 kg/a) or Toulouse and Bordeaux wastewater effluents (42-57 kg/a). This work is a basis for future work on Ag (including nanoparticles) cycles and related risks in aquatic systems (quantification, transfer and toxicity)

Silver : sources, transfer and bioaccumulation : case of the Gironde fluvio-estuarine system

Les rejets d’argent (Ag) dans l’environnement liés à l’exploitation minière aux diverses applications industrielles (e.g. bijouterie, médecine, photographie, électronique et plus récemment les nanotechnologies) font de Ag un polluant historique et émergent, dont les transferts et les effets dans les milieux aquatiques sont largement sous-documentés. Ce travail présente un premier bilan des sources, du transfert et de la bioaccumulation de Ag dans le système fluvio-estuarien de la Gironde. Le continuum Lot-Garonne-Gironde, connu pour une pollution polymétallique (e.g. Cd, Zn) provenant du bassin de Decazeville, est un système modèle pour l’étude des transferts métalliques du continent à l’océan. Les enregistrements des signaux historiques (~50 ans) de Ag dans les sédiments du Lot en amont (Ag : 0,3 mg/kg) et en aval (Ag : jusqu’à 7 mg/kg) du bassin de Decazeville sont similaires à ceux de Cd, indiquant des sources et des processus de transport/dépôt communs liés à l’histoire minière et industrielle jusqu’en 1986. Le lessivage et l’érosion actuels des terrils provoquent localement des concentrations en Ag particulaire (AgP : 260 mg/kg) et dissous (AgD : 1260 ng/l) dans la rivière Riou-Mort qui sont 2 à 3 ordres de grandeur supérieures aux valeurs typiques. Malgré ces fortes concentrations, la contribution du Riou-Mort aux flux de Ag de la Garonne (AgD : 0,008 à 0,041 t/an ; AgP : 0,306 à 2,44 t/an ; 1999-2009) reste faible (AgP : <11% ; AgD : <6%). La Garonne transporte l’essentiel (63-83%) des apports en Ag à l’estuaire principalement sous forme particulaire (96±2%). La détermination du bruit de fond géochimique régional (AgP/ThP=0,026) a permis d’évaluer (i) la contribution naturelle (20% à 65%) aux flux totaux en AgP et (ii) les flux anthropiques spécifiques de AgP (15±10 g/km²/an et 0,24±0,16 g/hab/an) à l’échelle du bassin versant de la Garonne (La Réole). Dans l’estuaire salin, la désorption par les ions chlorures libère ~60% de AgP vers la colonne d’eau (addition), provoquant des concentrations maximales en AgD (6-8 ng/l) à salinité 15-25. La fraction en Ag désorbé correspond à la fraction potentiellement biodisponible ou réactive (i.e. extractible par HCl 1 M). Ainsi, les premières estimations des flux nets indiquent que l’export annuel de Ag vers le domaine côtier est à 50-80% lié à la phase dissoute (0,64 à 0,89 t/an en 2008 et 0,56 à 0,77 t/an en 2009). Bien que plus biodisponible sous forme ionique Ag+ (dominante en eau douce), l’accumulation de Ag dans les organismes estuariens (huîtres, crevettes et anguilles) reflète la pression d’exposition supérieure en eau saumâtre. L’exposition in situ d’anguilles européennes, espèce recommandée pour la biosurveillance du milieu dans le cadre de la Directive Cadre sur l’Eau, dans des cages à différents sites clé de l’estuaire pendant 3 mois, a mis en évidence les voies directes et trophiques de la contamination en Ag à des niveaux de contamination environnementaux. L’enregistrement historique de la contamination en Ag des huîtres de la Gironde (1979-2007, RNO, Ifremer) indique que le bassin de Decazeville a été la source majoritaire en Ag jusqu’en ~1988. Cependant, l’accumulation maximale de Ag dans ces bivalves après 1993 (de ~40 à plus de 100 mg/kg, poids sec) révèle une contribution croissante de sources additionnelles et contemporaines en Ag comme la photographie, l’ensemencement des nuages (30 à 63 kg/an) ou encore les rejets des eaux usées urbaines de Toulouse et de Bordeaux (42 et 57 kg/an). Ce travail constitue une base nécessaire à l’étude des rejets du cycle de Ag (y compris les nanoparticules) dans le milieu aquatique (quantification, transfert et toxicité) et des risques associés.Silver (Ag) emissions into the environment from former mining activities and various industrial applications (e.g. jewellery, medicine, photography, electronic products and more recently nanotechnology) make Ag both a historic and an emergent pollutant for which information on its transfer and toxicity in aquatic system are scarce. This work provides a first assessment of Ag sources, transfer and bioaccumulation in the Gironde fluvial-estuarine system. The Lot-Garonne-Gironde River continuum, known for its polymetallic pollution (e.g. Cd, Zn) derived from the Decazeville basin, is a model system for studies on metal transfer from watersheds to the ocean. The relationship between historical records (~50 years) of Ag concentrations in sediment cores from the Lot River, upstream (Ag: 0.3 mg/kg) and downstream (Ag: up to 7 mg/kg) of the Decazeville basin and those of Cd constitutes evidence of a common source and transport/settlement processes due to industrial activities until 1986. High particulate Ag (AgP: 260 mg/kg) and dissolved Ag (AgD: 1,260 ng/l) concentrations in the Riou-Mort River were attributed to current leaching and erosion of slag heaps by rainwater. Those concentrations were 2 to 3 orders of magnitude greater than typical values in the Gironde watershed. However, the Riou-Mort River contribution to the Garonne River Ag fluxes (AgD: 0.008-0.041 t/a; AgP: 0.306-2.44 t/an; 1999-2009) remained low (AgP: <11%; AgD: <6%). The Garonne River provided the quasi totality (63-83%) of Ag inputs to the estuary, mainly in its particulate form (96±2%). The regional geochemical background (AgP/ThP=0.026) was useful to estimate (i) the natural contribution (20-65%) to total AgP fluxes and (ii) the anthropogenic specific fluxes of AgP (15±10 g/km²/a and 0.24±0.16 g/hab/a) in the Garonne watershed (La Réole). In the estuarine salinity, chloro-complexation desorbed ~60% of AgP, causing maximalum AgD concentrations (6-8 ng/l) at salinity 15-25 (addition to the dissolved phase). This quantity was similar to the potentially bioavailable or reactive fraction (i.e. extracted by HCl 1 M). The first estimations of net fluxes suggested that 50-80% of the Ag annual export to the coast occurred in the dissolved phase (0.64-0.89 t/a in 2008 and 0.56-0.77 t/a in 2009). Even if the ionic form Ag+ (the main form in freshwater) is considered as the most bioavailable form, Ag accumulation in estuarine organisms (oysters, shrimps and eels) reflected the higher exposition pressure in brackish water. In-situ caging of European Eels (recommended species for the biosurvey of aquatic systems; European Water Framework Directive) in key sites of the Gironde Estuary during 3 months, highlighted the direct and trophic pathways of Ag contamination at the environmental level. The historical record of Ag contamination of the Gironde Estuary oysters (1979-2007, French Mussel Watch, RNO) indicated that the Decazeville basin was a major Ag source until ~1988. However, the maximum Ag accumulation in oysters after 1993 (from ~40 to more than 100 mg/kg, dry weight) suggested an increasing contribution of additional and contemporary Ag sources like photography, cloud seeding (30-63 kg/a) or Toulouse and Bordeaux wastewater effluents (42-57 kg/a). This work is a basis for future work on Ag (including nanoparticles) cycles and related risks in aquatic systems (quantification, transfer and toxicity)

Multi‐residue analysis of 44 pharmaceutical compounds in environmental water samples by solid‐phase extraction coupled to liquid chromatography‐tandem mass spectrometry

International audienceA solid‐phase extraction combined with a liquid chromatography‐tandem mass spectrometry analysis has been developed and validated for the simultaneous determination of 44 pharmaceuticals belonging to different therapeutic classes (i.e., antibiotics, anti‐inflammatories, cardiovascular agents, hormones, neuroleptics, and anxiolytics) in water samples. The sample preparation was optimized by studying target compounds retrieval after the following processes: i) water filtration, ii) solid phase extraction using Waters Oasis HLB cartridges at various pH, and iii) several evaporation techniques. The method was then validated by the analysis of spiked estuarine waters and wastewaters before and after treatment. Analytical performances were evaluated in terms of linearity, accuracy, precision, detection, and quantification limits. Recoveries of the pharmaceuticals were acceptable, instrumental detection limits varied between 0.001 and 25 pg injected and method quantification limits ranged from 0.01 to 30.3 ng/L. The precision of the method, calculated as relative standard deviation, ranged from 0.3 to 49.4%. This procedure has been successfully applied to the determination of the target analytes in estuarine waters and wastewaters. Eight of these 44 pharmaceuticals were detected in estuarine water, while 26 of them were detected in wastewater effluent. As expected, the highest values of occurrence and concentration were found in wastewater influent

Simultaneous determination of 42 pharmaceuticals in seafood samples by solvent extraction coupled to liquid chromatography–tandem mass spectrometry

International audienceAn efficient and sensitive analytical method based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) has been developed and validated for the simultaneous determination of 42 pharmaceuticals belonging to different therapeutic classes (i.e. antibiotics, analgesics, anti-inflammatories, cardiovascular agents, anxiolytics and human indicators) in seafood samples. The very simple sample preparation included analytes extraction with acidified methanol, concentration by evaporation and filtration of the final extract prior to LC–MS/MS analysis. Analytical performances were evaluated in muscles of four commercial species (hake, red mullet, sole and shrimp) and showed good recoveries at two spiked concentration levels, with relative standard deviations below 45%. Limits of quantification ranged from 0.1 to 40.2 ng/g. This procedure has been successfully applied to the determination of the target analytes in seafood collected from the Bay of Biscay (Southern France) and 4 of these 42 pharmaceuticals were detected at low ng/g levels, suggesting a very limited contamination

Synthetic musk in seafood products from south Europe using a quick, easy, cheap, effective, rugged and safe extraction method

International audienceThis study aims at developing a method for the determination of 9 synthetic musk compounds in seafood products by combining the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and determination by gas chromatography mass spectrometry (GC-EI-MS). Method detection limits (MDL) ranging between 0.001 and 1.94 ng g-1 were obtained. The linearity is higher than 0.9899 in the range MDL - 100 ng g-1 with precision below 18% and recoveries between 46% and 120% were obtained. The method was applied to quantify musk compounds in seafood products from the European southwest coast (oysters, mussels, salmon organs, glass eels). Galaxolide and Tonalide exhibited the highest concentration levels ranging between MDL - 96.4 ng g-1 and MDL - 6.85 ng g-1, respectively. Contamination levels observed for the two nitro musks (musk xylene and musk ketone) are significantly lower ranging between MDL - 0.6 ng g-1 and MDL - 0.09 ng g-1, respectively. Analysis of different organs of salmons showed higher concentrations in liver and gonad than in muscle tissues. © 2016 Elsevier Ltd. All rights reserved

Determination of Synthetic Musks in Surface Sediment from the Bizerte Lagoon by QuEChERS Extraction Followed by GC-MS

International audienceA new analytical method for the simultaneous determination of eight synthetic musks compounds (SMs) including five polycyclic musks (PCMs) and three nitro musks (NMs) was validated for sediment samples based on a simple QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) sample preparation procedure followed by gas chromatography–mass spectrometry (GC–MS). Good analytical performances were obtained for all the target compounds. For the validation of the method, internal calibration (IC) and internal calibration with QuEChERS (ICQ) were compared. Good linearity was obtained for both calibration methods with determination coefficients (R2) ranging between 0.990 for Musk Xylene (MX) and 0.999 for Tonalide (AHTN) with IC and between 0.991 for Musk Ketone (MK) and 0.999 for Traseolide (ATII) with ICQ. The repeatability ranges were 0.1 %–1.9 % with the IC and 0.1 %–2.6 % with the ICQ. The apparent recoveries obtained for SMs in the standard reference sediment (SRM1944) varied in the range of 70 %–98 % and 75 %–103 % in the sediment from the Bizerte Lagoon (Tunisia). The absolute recoveries ranged between 61 % and 92 % for the SRM1944 and between 61 % and 89 % in the sediment from the Bizerte Lagoon. The limits of detection (LOD) calculated for the two main compounds, Galaxolide (HHCB) and Tonalide (AHTN) were 0.3 and 0.1 ng g−1 respectively. The LODs obtained for ADBI (Celestolide), AHMI (Phantolide), ATII (Traseolide), MM (Muks mosken), MK (Musk Ketone) and MX (Musk Xylene) were 0.08, 0.12, 0.03, 0.34, 0.11, 0.08, 0.10 and 0.15 ng g−1 respectively. The levels of ∑SMs in surface sediments from the Bizerte Lagoon ranged from 1.4 to 4.5 ng g−1, which are 1000 times lower that the predicted no effect concentration (PNEC) for marine organisms

Impact of Old and Recent Gold Mining Sites on Mercury Fluxes in Suspended Particulate Matter, Water and Sediment in French Guiana

International audienceIn 2006 the use of mercury (Hg) was banned for gold mining in French Guiana. However, mining of old placers could mobilize Hg accumulated in soils and sediment. This study aimed to measure the current impact of a mining concession (Boulanger site) on the Hg load in the watershed. Turbidity, Total Mercury (THg), and Monomethylmercury (MMHg) were measured in water, suspended particulate matter (SPM), river sediment and sediments from old tailing ponds along a river section of 30 km up and downstream from a mining concession in French Guiana during a dry and a rainy season. Total dissolved Hg (THg D) concentrations varied little from up-to downstream but were all higher (fourfold on average) during the rainy season (3.2 to 4.4 ng L −1), than during the dry season and consistent with previous data known for the Amazonian area. Dissolved MMHg (MMHg D) represented up to 30% of THg D during the dry season, which is higher than previous results (typically around 2%). Mercury concentrations in sediments were highest in the vicinity of areas affected by old (before 2006) rather than new gold mining practices. Even though Hg was banned in 2006, present gold mining practices still release natural Hg and Hg inherited from older mining practices into the watershed

Priority and emerging micropollutants in sediments of Capbreton Canyon (SW France)

International audiencePriority substances set by the Water Framework Directive (WFD) are of major interest to evaluate the quality of coastal and marine systems, the final receptors for pollutant emissions. Emerging substances not regulated by the WFD, i.e. personal care products and pharmaceuticals, are of high concern since only scarce information of their occurrence, reactivity and impact are available in themarine environment.A large screening of micropollutants has been achieved in surface sediments collected in the Canyon of Capbreton (Gulf of Biscay). Twenty-four stations have been sampled within the first 30 km of the canyon in July 2017. Occurrence andconcentrations of priority (PAHs, PCBs, OCPs and trace metal) and emerging micropollutants (synthetic musks and sunscreens compounds) have been determined. In addition, sediments collected at three different depths were used to perform incubation experiments with a synthetic musk (HHCB) or a sunscreen compound (OD-PABA). Experiments have been performed at 12°C in the dark, controls have been also conducted with sterilized sediments. Some priority substances were lower than the detection limits whereas PAHsand PCBs exhibited high concentration levels ranging from 199 to 7,116 ng.g-1 and from 0.1 to 18.6 ng.g-1, respectively. Emerging micropollutants were measured at low concentrations. Musk compounds (HHCB, AHTN and MK) concentrations were up to 3.6, 2.3 and 7.0 ng.g-1, respectively. Sunscreens (3-BC, 4-MBC, EHMC and OC) concentrations were up to 6.2, 9.2, 31.8 and 29.2 ng.g-1, respectively. Highest concentrations were observed for offshore stations. Sediments from terraces or slopes of the canyon exhibited higher levels compared to those from the continental shelf. Degradation potentials have been only observed under biotic condition for OD-PABA suggesting the involvement of biologically mediated mechanism

Adaptation and validation of QuEChERS method for the simultaneous analysis of priority and emerging pollutants in sediments by gas chromatography—mass spectrometry

<p>A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method has been adapted and validated for the simultaneous determination of priority (16 PAHs, 12 PCBs and 7 organochlorine pesticides (OCPs)) and emerging (carbamazepine, 9 musks and 6 sunscreens) pollutants in sediments by Gas Chromatography-Mass Spectrometry (GC-MS). The sample preparation was adapted by modifying the nature of the extraction solvent and optimising clean-up and evaporation steps. The method was validated by the analysis of spiked estuarine and marine sediments. Analytical performances were evaluated in terms of linearity, accuracy, precision and detection limits. The method shows good linearity (coefficients of determination > 0.998) and repeatability (RSD < 10%). Obtained recoveries are acceptable, ranging from 62% to 131% for all the compounds. Detection limits are estimated to range from 0.01 ng/g to 3.18 ng/g. This developed method offers the ability to detect and quantify several priority and emerging pollutants at low concentration levels in sediments.</p

Mercury concentrations in suspended particulate matter, water and mud-sediment up and downstream from old and recent gold mining sites in French Guiana

International audienceAlthough the use of mercury (Hg) for gold mining has been officially banned in French Guiana since 2006, there are still reasons to be wary of its occurrence in river water and its impact on local populations. In fact, gold-mining generates intense soil erosion and high turbidity in the rivers downstream from mining sites. This contributes to Hg pollution and dissemination both via the remobilization of Hg naturally present in the soils and the release of metallic Hg from the gold recovery process. In the affected rivers, Hg transport and speciation is mainly controlled by the suspended particulate matter (SPM) rather than remaining dissolved.The aim of this study is to understand and quantify the fate of this SPM-associated Hg along the Boulanger River affected by old and new gold mining activities. Furthermore we provide recent data (2012) essential to evaluate the efficiency of legal gold mining companies in restoring and re-planting exploited zones to control erosion, river turbidity and SPM transport.Inorganic Hg(II), monomethylmercury (MMHg) and turbidity measurements were measured in water, SPM and mud-sediment collected along the Boulanger River, from the spring down to its confluence with the Orapu River. The intensity of gold-mining in this area has been up and down through the last century and presents contrasting conditions with old and recently exploited areas.Dissolved Hg (HgD) levels were low (1-2 ng.L-1) and consistent with previous data known for the Amazonian area. Dissolved MMHg concentrations represented up to 8% of HgD which is higher than previous results (around 2%). Some relationships occurred between Hg concentrations in mud-sediment and turbidity values which both decreased downstream from the mining sites, then stabilized at 4-5 km further down. Hg contents in the mud-sediment show the impact of old and new gold mining practices. These results show that even though Hg use was banned from French Guiana 6 years ago, present gold mining practices still release significant amounts of Hg into the rivers. Survey intensification in French Guiana river systems should provide a more complete data set, essential to change gold mining practices and to reduce SPM and Hg contamination of the aquatic environment