[show abstract][hide abstract] ABSTRACT: Concentrations of inorganic tin (Sninorg), tributyltin (TBT) and its degradation products dibutyltin (DBT) and monobutyltin (MBT) were measured in surface sediments and in two cores from the Toulon Bay, hosting the major French military harbour. Anticipating planned dredging, the aim of the present work is to map and evaluate for the first time the recent and historic contamination of these sediments by inorganic and organic Sn species derived from antifouling paints used for various naval domains including military, trade, tourism and leisure. Tin and butyl-Sn concentrations in the bay varied strongly (4 orders of magnitude), depending on the site, showing maximum values near the shipyards. The concentrations of total Sn (1.3-112 μg g(-1)), TBT (<0.5-2,700 ng g(-1)), DBT (<0.5-1,800 ng g(-1)) and MBT (0.5-1,000 ng g(-1)) generally decreased towards the open sea, i.e. as a function of both distance from the presumed main source and bottom currents. Progressive degradation state of the butyl-Sn species according to the same spatial scheme and the enrichment factors support the scenario of a strongly polluted bay with exportation of polluted sediment to the open Mediterranean. Low degradation and the historical records of butyl-Sn species in two (210)Pb-dated sediment cores, representative of the Northern Bay, are consistent with the relatively recent use of TBT by military shipyards and confirm maximum pollution during the 1970s, which will persist in the anoxic sediments for several centuries. The results show that (a) degradation kinetics of butyl-Sn species depend on environmental conditions, (b) the final degradation product SninorgBT is by far the dominant species after 10-12 half-life periods and (c) using recent data to reliably assess former TBT contamination requires the use of a modified butyl-Sn degradation index BDImod. Resuspension of extremely contaminated subsurface sediments by the scheduled dredging will probably result in mobilization of important amounts of butyl-Sn species.
Environmental Science and Pollution Research 02/2014; · 2.62 Impact Factor
[show abstract][hide abstract] ABSTRACT: Total and HCl-available (extracted by HCl 1 M) trace metal (V, Cu, As, Cd, Pb and Th) concentrations were measured in suspended particulate matter (SPM) and surface sediments from the Garonne and the Charente Rivers (Southwest France), from their respective estuaries and from the adjacent coastal zone including the Marennes Oleron Bay. The objectives were to explore the potential of trace element signatures in the residual (non-reactive) fraction to trace the origin of particles, i.e. major contaminant carriers, in complex coastal systems. The observation period covered 12 months and a wide range of hydrological conditions.
Selective extractions (HCl 1 M) showed that Pb, Cd and Cu in SPM and surface sediments from the entire system, including freshwater and marine environments, were highly reactive with potentially available fractions representing 64±13 %, 60±18 % and 43±13 %, of the respective total metal concentrations. In contrast, V, As and Th showed low reactivity, with potentially available fractions lower than 19±7%, 11±3 %, and 1.6±0.9 %, respectively. Two combinations of Th-normalised (i.e. grain size corrected) metal concentrations in the residual fraction (Vres + Asres)/Thres and (Cdres + Cures +Pbres)/Thres represented two distinct signatures corresponding to the Charente and Garonne River endmembers. The respective Mres signals showed that both SPM and surface sediments sampled in the Marennes Oleron Bay mainly (>54%) originated from the Gironde Estuary watershed. Furthermore, SPM from the tidal ranges of the Charente Estuary contained close to 100% of particles from the Gironde watershed. These results, together with SPM flux estimates for the Charente River, suggest that particle transport from the Gironde Estuary to the Marennes Oleron Bay accounts for 81 000 t a−1 to 435 000 t a−1, representing 5% to 29% of the total SPM expulsed by the Gironde Estuary. Application of this novel approach to determine SPM and sediment origin to other aquatic environments may require adapting the choice and association of residual metal concentrations.
Continental Shelf Research 01/2014; 72:119-130. · 1.89 Impact Factor
[show abstract][hide abstract] ABSTRACT: The main carrying phases of mercury (Hg) were analyzed in a 120 cm sediment core taken at the Laguna del Plata (LP), a small lake connected to the main water body of Laguna Mar Chiquita (LMC) during highstands. LMC is considered to be one of the largest saline lakes in the world representing a sensitive climatic indicator due to its frequent lake level variations at millennial and interdecadal scale like the last ones that started early in the 1970s and after 2004. Total particulate Hg (HgTP) concentrations vary between ∼13 and ∼131 μg kg−1 indicating a system with low pollution. Selective extractions with ascorbate, HCl and H2O2 were performed in the sediments and they revealed that Hg is associated mainly to reactive sulphides in the base of the core, while in the middle and upper part the organic matter seems to be the main Hg-bearing phase. The highest and most important peak was found in sediments accumulated between 1991 and 1995. More than a punctual source of pollution, this peak is likely related to two eruptive events occurred in the Andean Cordillera in this period: the eruption of Hudson volcano in southern Patagonia that occurred in 1991 and the one of the Láscar volcano in northern Chile that occurred in 1993. In both cases, the respective ash plumes were documented to have reached the Laguna del Plata region.
[show abstract][hide abstract] ABSTRACT: This article presents the results of multidisciplinary research (geochemistry, sociology) into the increasing concentrations of silver (Ag and nanoAg) in the environment and their potential impact on aquatic environments. We investigate simultaneously the risk of contamination of these environments by silver and the process of the social and political construction of this risk by water managers, health authorities, agencies and committees responsible for expert evaluations, environmental associations, and potential users of silver or nano-silver. Four updated models of risk construction allow us to understand the logic of arguments mobilized at this stage of the emerging risk. This interdisciplinary cooperation opens up possibilities for dealing with some environmental health issues; it highlights the benefits of an approach aiming to disseminate knowledge to enable action and to promote awareness and analysis by the local stakeholders and officials who face this emerging problem.
[show abstract][hide abstract] ABSTRACT: High precision MC-ICP-MS Cu isotope measurements were performed on suspended particulate matter (SPM) and filtered water sampled along the turbidity gradient of the fluvial Gironde Estuary (Garonne Branch), following a summer lasting period of low freshwater discharge. High Cu concentrations (up to ~ 200 μg/g) in particulate organic carbon (POC)-rich (up to ~ 14%) particles upstream from the Maximum Turbidity Zone (MTZ) coincide with the most negative δ65Cu values (down to - 0.39‰). This suggests the preferential uptake of light Cu isotopes by phytoplankton or anthropogenic contamination from CuSO4 fungicides related to intensive wine farming in the area (δ65Cu = - 0.37‰ for vineyard soils). Suspended particulate matter samples in the MTZ exhibit lower Cu concentrations (~ 35 μg/g) and heavier isotopic compositions (δ65Cu = - 0.20‰ in average), as recorded by other samples from the Gironde Watershed. Along the fluvial estuary, dissolved Cu isotopes are mostly enriched in heavy isotopes (up to δ65Cu = + 0.21‰), but negative signatures down to δ65Cu = - 0.66‰ occur near the city of Bordeaux. Release of dissolved Cu was attributed to the mineralization of organic matter with a total addition of ~ 600 ng/L in the fluvial estuary. Continuously decreasing amounts of dissolved Cu added with distance, suggest that the observed Cu release evolved towards completion in the MTZ and contributed to negative values for dissolved Cu isotopes, as modeled by a Rayleigh process. Urban wastewater effluents probably also contribute to both (i) the dissolved Cu addition (10-20%) in the MTZ and (ii) negative Cu isotope signatures. Further work is necessary to assess the respective roles of anthropogenic sources and biogeochemical fractionation processes. Accordingly, the present study provides new insights into the potential of Cu isotopes for fingerprinting sources and mechanisms involved in the biogeochemical cycle of Cu in temperate aquatic environments impacted by anthropogenic activities
[show abstract][hide abstract] ABSTRACT: Aiming at increasing the resolution of otolith tracers, we investigated the possibility to use Mn, Co, Zn, Rb, Cd, Sn, Ba, Sr, and Pb otolith composition to retrieve the movements of eels (Anguilla anguilla) in the lower Gironde watershed. Caging experiments were designed to validate the site specific otolith signatures. Individually identified eels were reared in cages in three locations along the estuarine and river gradient. Three trials were set up for successive periods of 3months and 6months. Water Mn, Co, Zn, Rb, Cd, Sn, Ba, Sr, and Pb concentrations were monitored. The eel otolith composition corresponding to the experimental period was measured with an ICPMS coupled with a femtosecond laser. Liver Cd, Zn and Pb concentrations were measured. For each caging experiments, we tested the influence of individual weight gain, caging site and trial on elemental otolith concentrations. Mn, Co, Zn, Rb, Cd, Sn, Ba, Sr, and Pb were detected in eel otolith above the detection limits. Otolith Sr and Ba concentrations significantly discriminated the caging sites for one trial. Individual weight gain did not have a significant influence on otolith elemental concentrations. Co, Rb, Cd, Sn, Zn, Sr and Ba otolith concentrations were significantly influenced by the trials. Water elemental composition was only partly reflected by otolith elemental composition. The results showed that otolith composition had a more integrative value than water composition. Complex elemental seasonal variations and individual eel incorporation potential complicated the interpretation of otolith composition. Liver and otolith Cd and Zn concentrations did not show a statistically significant correlation.
Science of The Total Environment 09/2012; 437:323-30. · 3.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: Dissolved and particulate Ag concentrations (Ag(D) and Ag(P), respectively) were measured in surface water and suspended particulate matter (SPM) along the salinity gradient of the Gironde Estuary, South West France, during three cruises (2008-2009) covering contrasting hydrological conditions, i.e. two cruises during intermediate and one during high freshwater discharge (~740 and ~2,300 m(3)/s). Silver distribution reflected non-conservative behaviour with 60-70 % of Ag(P) in freshwater particles being desorbed by chlorocomplexation. The amount of Ag(P) desorbed was similar to the so-called reactive, potentially bioavailable Ag(P) fraction (60 ± 4 %) extracted from river SPM by 1 M HCl. Both Ag(P) (0.22 ± 0.05 mg/kg) and Ag(P)/Th(P) (0.025-0.028) in the residual fraction of fluvial and estuarine SPM were similar to those in SPM from the estuary mouth and in coastal sediments from the shelf off the Gironde Estuary, indicating that chlorocomplexation desorbs the reactive Ag(P). The data show that desorption of reactive Ag(P) mainly occurs inside the estuary during low and intermediate discharge, whereas expulsion of partially Ag(P)-depleted SPM (Ag(P)/Th(P) ~0.040) during the flood implies ongoing desorption in the coastal ocean, e.g. in the nearby oyster production areas (Marennes-Oléron Bay). The highest Ag(D) levels (6-8 ng/L) occurred in the mid-salinity range (15-20) of the Gironde Estuary and were decoupled from freshwater discharge. In the maximum turbidity zone, Ag(D) were at minimum, showing that high SPM concentrations (a) induce Ag(D) adsorption in estuarine freshwater and (b) counterbalance Ag(P) desorption in the low salinity range (1-3). Accordingly, Ag behaviour in turbid estuaries appears to be controlled by the balance between salinity and SPM levels. The first estimates of daily Ag(D) net fluxes for the Gironde Estuary (Boyle's method) showed relatively stable theoretical Ag(D) at zero salinity (Ag (D) (0) = 25-30 ng/L) for the contrasting hydrological situations. Accordingly, Ag(D) net fluxes were very similar for the situations with intermediate discharge (1.7 and 1.6 g/day) and clearly higher during the flood (5.0 g/day) despite incomplete desorption. Applying Ag (D) (0) to the annual freshwater inputs provided an annual net Ag(D) flux (0.64-0.89 t/year in 2008 and 0.56-0.77 t/year in 2009) that was 12-50 times greater than the Ag(D) gross flux. This estimate was consistent with net Ag(D) flux estimates obtained from gross Ag(P) flux considering 60 % desorption in the estuarine salinity gradient.
Environmental Science and Pollution Research 07/2012; · 2.62 Impact Factor
[show abstract][hide abstract] ABSTRACT: Municipal wastewater (WW) discharges induce various environmental impacts on receiving freshwater systems e.g. contribution to metal pollution. Besides the quantity of metal release, metal speciation and possible transformation processes present danger to aquatic biota. In experimental mixtures of WW effluents with receiving waters, discharged dissolved trace metals showed different forms of behavior. Cobalt showed adsorption onto particles, while Cu showed desorption from particulate into dissolved state. In presence of high amounts of river particles, interactions with WW contaminants were elevated.
URBAN ENVIRONMENT Alliance for Global Sustainability Bookseries. 01/2012; Volume 19(Part 3):339-349.
[show abstract][hide abstract] ABSTRACT: Arsenic-rich (~140-1520 mg x kg(-1)) suspended particulate matter (SPM) was collected daily with an automatic sampler in the Upper Isle River (France) draining a former gold mining district in order to better understand the fate of arsenic during the suspended transport (particles smaller than 50 μm). Various techniques at a micrometric scale (EPMA, quantitative SEM-EDS with an automated particle counting including classification system and μXRD) were used to directly characterize As-bearing phases. The most frequent ones were aggregates of fine clay particles. Their mineralogy varied with particle sources involved. These aggregates were formed by chlorite-phlogopite-kaolinite assemblages during the high flow and chlorite-illite-montmorillonite during the low flow. Among all the observed As-carriers in SPM, these clay assemblages were the least As-rich (0.10 up to 1.58 wt.% As) and their median As concentrations suggested that they were less concentrated during the high flow than during the low flow. Iron oxyhydroxides were evidenced by μXRD in these clay aggregates, either as micro- to nano-sized particles and/or as coating. (Mn, Fe)oxyhydroxides were also present as discrete particles. Manganese oxides (0.14-1.26 wt.% As) transport significantly more arsenic during the low flow than during the high flow (0.16-0.79 wt.% As). The occurrence of Fe oxyhydroxide particles appeared more complex. During the low flow, observations on banks and in wetlands of freshly precipitated Fe hydroxides (ferrihydrite-type) presented the highest As concentrations (up to 6.5 wt.% As) but they were barely detected in SPM at a microscale. During the high flow, As-rich Fe-oxyhydroxides (0.10-2.80 wt.% As) were more frequent, reflecting mechanical erosion and transport when the surface water level increased. Arsenic transfers from SPM to corresponding aqueous fraction mostly depend on As-carrier stability. This study shows the temporal occurrence of each type of As-bearing phases in SPM, their As concentrations at a particle scale and abundance according to hydrological periods.
Science of The Total Environment 09/2011; 409(23):4986-99. · 3.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Gironde fluvial estuarine system is impacted by historic metal pollution (e.g. Cd, Zn, Hg) and oysters (Crassostrea gigas) from the estuary mouth have shown extremely high Cd concentrations for decades. Based on recent work (Chiffoleau et al., 2005) revealing anomalously high Ag concentrations (up to 65 mg kg(-1); dry weight) in Gironde oysters, we compared long-term (~1955-2001) records of Ag and Cd concentrations in reservoir sediment with the respective concentrations in oysters collected between 1979 and 2010 to identify the origin and historical trend of the recently discovered Ag anomaly. Sediment cores from two reservoirs upstream and downstream from the main metal pollution source provided information on (i) geochemical background (upstream; Ag: ~0.3 mg kg(-1); Cd: ~0.8 mg kg(-1)) and (ii) historical trends in Ag and Cd pollution. The results showed parallel concentration-depth profiles of Ag and Cd supporting a common source and transport. Decreasing concentrations since 1986 (Cd: from 300 to 11 mg kg(-1); Ag: from 6.7 to 0.43 mg kg(-1)) reflected the termination of Zn ore treatment in the Decazeville basin followed by remediation actions. Accordingly, Cd concentrations in oysters decreased after 1988 (from 109 to 26 mg kg(-1), dry weight (dw)), while Ag bioaccumulation increased from 38 up to 116 mg kg(-1), dw after 1993. Based on the Cd/Ag ratio (Cd/Ag~2) in oysters sampled before the termination of zinc ore treatment (1981-1985) and assuming that nearly all Cd in oysters originated from the metal point source, we estimated the respective contribution of Ag from this source to Ag concentrations in oysters. The evolution over the past 30 years clearly suggested that the recent, unexplained Ag concentrations in oysters are due to increasing contributions (>70% after 1999) by other sources, such as photography, electronics and emerging Ag applications/materials.
[show abstract][hide abstract] ABSTRACT: Sediments quality assessment is of priority concern to provide a comprehensible overview of ecological and chemical state of an ecosystem. The Marennes-Oléron Bay, hosting the largest oyster production in France, is influenced by the historic polymetallic pollution of the Gironde Estuary. Despite, management efforts and decreasing emissions in the Gironde watershed, Cd levels in oysters from the bay are close to consumption limit (5μgg−1 dw, EC no. 466/2001). In this context, the aim of the study was to assess the priority metal (Ni, Cu, Zn, As, Ag, Cd, Hg, Pb and Th) concentrations in sediment within the Bay, by investigating spatial and temporal distribution variations and the role of hydrodynamic forcing. For that we selected three sites (east, west and south) characterizing different environments of the Bay and we observed metal concentrations, grain size distribution, bed elevation and wave activities during a year survey. The sampling strategy pointed out both spatial and temporal metal concentrations variability in sediment. In general, metal enrichments were close to geochemical background. The eastern part of the Bay, largely influenced by the Charente river particulate deposition, presented constant concentrations over the survey. In contrast, in the western part, bed elevation was strongly influenced by hydrodynamic forcing especially wave activities, and metal distribution showed constant metal concentrations except very located Cd minor enrichment related to the Gironde influence via the Antioche Strait (north). The southern part was disconnected from the rest of the Bay and showed minor to very located moderately severe Cd enrichment, related to the Gironde water discharges via the Maumusson Strait (south). Thus, the multi-disciplinary approach was relevant to characterize the interactions between hydrodynamic forcing on the environment and sediments and their metal quality state which (i) were close to geochemical background over a year for Ni, Cu, Zn, As, Ag, Hg and Pb (i) which presented enrichment of Cd in the western and southern part.
Continental Shelf Research 06/2011; 31(9):997-1007. · 1.89 Impact Factor
[show abstract][hide abstract] ABSTRACT: Ecotoxicological studies aim to assess the potential environmental risks of various products. This implies the use of various biological models and tests on live animals. In case of handling fish and mammals, ethical rules have to be respected. The use of anaesthesia is considered to be the best way to ensure animal welfare. Eugenol and electro-narcosis are among the most popular chemical and physical anaesthetics used in fisheries and by field biologists. In this study, the genetic and endocrine impacts of these anaesthetics were assessed in order to establish whether the use of such methods could skew the results of ecotoxicological studies. Twenty yellow European eels (Anguilla anguilla) were submitted to Eugenol (50mg/L) and electro-narcosis until they reached a level of deep anaesthesia, while 20 other eels were kept aware. Five anaesthetized and five unanaesthetized eels were sacrificed and analysed directly after treatment and after 1, 7 and 21 days of recovery. At the brain level, Eugenol triggered an increase in the transcription level of genes encoding proteins involved in oxidative stress responses (catalase expression 2.5-fold, mitochondrial superoxide dismutase expression 3-fold), probably due to a hypoxic event during anaesthesia. Later impacts were detected in muscles 21 days after anaesthesia (ATP synthase subunit 6 3-fold, NADH deshydrogenase subunit 5 4-fold and mitochondrial superoxide dismutase 3-fold increased) revealing oxidative stress from an accrued mitochondrial respiratory metabolism. Hormone dosages showed that the use of Eugenol reduced the release of plasma cortisol during anaesthesia. However, this impact seemed to be reversible within one day. In case of electro-narcosis, no significant variation in transcriptional levels could be detected between anaesthetized and unanaesthetized eels. Our results suggest that the use of Eugenol as an aesthetic in ecotoxicological studies measuring gene expression or plasma cortisol concentration is not appropriate, while electro-narcosis does not seem to have any impact, at least on the parameters taken into consideration in this study.
Ecotoxicology and Environmental Safety 04/2011; 74(6):1573-7. · 2.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Marennes-Oléron Bay, hosting the largest oyster production in France, is influenced by the historic polymetallic pollution of the Gironde Estuary. Despite management efforts and decreasing emissions in the Gironde watershed, cadmium levels in oysters from the bay are close to the consumption limit (5 μg g(-1) dw, EC). From mid April to mid July 2009, we investigated the role of tidal resuspension and regional hydrodynamics on Cd speciation (seawater, SPM, phytoplankton, sediment, microphytobenthos) and bioaccumulation in 18 month-old oysters (gills, digestive glands, rests of tissues) reared under natural conditions (i) at ∼60 cm above the sediment and (ii) on the sediment surface. Dissolved and particulate Cd concentrations in surface and bottom waters were similar and constant over tidal cycle suggesting the absence of Cd release during sediment resuspension. Temporal dissolved and particulate Cd concentrations were closely related to Gironde Estuary water discharges, showing increasing concentrations during flood situations and decreasing concentrations afterwards. Cd depletion in the water column was associated with increasing Cd in the [20-100 μm] plankton fraction, suggesting Cd bioaccumulation. After 3 months, enrichment factors of Cd in tissues of oysters exposed in the water column and directly on the sediment were respectively 3.0 and 2.2 in gills, 4.7 and 3.2 in digestive glands and 4.9 and 3.4 in remaining tissues. Increasing Cd bioaccumulation in gills, digestive glands and remaining tissues can be related to elevated dissolved Cd in the bay, suggesting gill contamination via the direct pathway and subsequent internal redistribution of Cd to other organs and tissues. Elevated Cd contents in oysters reared on tables could be attributed to different trophic Cd transfer (phytoplankton versus microphytobenthos) or to different oyster metabolisms between the rearing conditions as suggested by metallothionein concentrations.
[show abstract][hide abstract] ABSTRACT: This study reports on the relationship between copper (Cu) behavior and organic matter (OM) transformation along the turbidity gradient in the freshwater reaches of the Gironde Estuary. During a one-year survey, surface water and suspended particulate matter (SPM) were sampled at least monthly at three sites along the Garonne Branch, representing the main fluvial branch of the Gironde Estuary. Additionally, a longitudinal high resolution profile was sampled along the Garonne Branch, covering the turbidity gradient from the river water endmember to the maximum turbidity zone (MTZ). Seasonal variability and spatial distribution of Cu in both the dissolved phases (<0.2 μm, Cu(0.2) and <0.02 μm, Cu(0.02)) and particulate Cu (Cu(P)) clearly suggested Cu(0.2) addition during summer, that increased the Cu(0.2) concentrations by a factor ~2, mainly manifested by an increase in the Cu(0.02) fraction. At the annual timescale (2004), this internal Cu reactivity increased Cu(0.02) fluxes in the Garonne Branch by ~20% (3.6 t year(-1)), with the equivalent of ~2.9 t year(-1) derived from the Cu(P) fraction and ~0.7 t year(-1) from the colloidal (0.02-0.2 μm) fraction, without involving and/or affecting the Cu(C18) (hydrophobic metal-organic complexes) fraction. Combining data on Cu speciation with the results obtained by several independent techniques (DOC and POC measurements, 3D-fluorescence, and TEM) suggested close relationships between Cu behavior and OM transformation/restructuration along the turbidity gradient in the Garonne Branch. The observed Cu(0.02) addition was related to increasing humification (humification index HIX increased from 9 to 12, network formation) and labile OM degradation (Iγ/Iα ratio decreased from 0.70 to 0.44), going along with decreasing DOC and POC concentrations. Mass-balances suggest that in the studied system, degradation of OM may account for the release of ~25 μmol potentially bioaccessible Cu(0.02) per mole of particulate organic carbon mineralized.
Science of The Total Environment 02/2011; 409(8):1539-49. · 3.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: The present work reports on the temporal variations of Sb, As, V and Mo concentrations in the surface freshwater reaches of the Gironde Estuary (SW France). Dissolved (<0.2 and <0.02 μm) and particulate Sb, As, V and Mo concentrations were measured in samples collected with high temporal resolution (every 30 min) during two consecutive tides at a fixed station located upstream of the city of Bordeaux and the maximum turbidity zone (MTZ). In addition, measurements of suspended particulate matter concentration, physico-chemical parameters, Cl− concentration, water depth, current velocity and particulate Th concentration were performed either at the same time resolution or continuously. The data obtained suggested that variations in particulate As, V and Mo concentrations were most probably related to tidal cycling near the sampling site of fine grained particles from the MTZ located downstream. Significant differences in the behavior of the dissolved target oxyanions, mostly present in the <0.02 μm fraction, occurred. The behavior of Sb was conservative. Variations of the dissolved As and V concentrations showed similar cycling trends, strongly related to tidal cycles. These As and V cycles were interpreted as a mixing between upstream freshwater and downstream water enriched in dissolved As and V by desorption from the MTZ particles. The observed trend in the variation of the dissolved Mo was more complex than that of As and Sb and attributed to the mixing of the water bodies mentioned above coupled to a point source input of dissolved Mo from an intra-estuarine source. The contribution of this suspected Mo source to the dissolved Mo concentrations measured at the sampling site was estimated from the ratio of dissolved Mo to dissolved As concentrations. The additional dissolved Mo signal, coupled to the monitored ebb and flood length and associated current velocities, suggested an anthropogenic input which may derive from industrial activity near the city of Bordeaux. Extrapolating these results to the annual scale suggested that this dissolved Mo may be equivalent to 45–90% of the annual dissolved Mo flux into the Garonne Branch, highlighting the importance to further investigate the origin and behavior of Mo in the fluvial estuary near Bordeaux.Highlights► Sb showed conservative behavior in the Garonne fluvial estuary. ► High temporal variations in dissolved As, V and Mo were observed at the tidal scale. ► These variations are due to equilibration processes in the MTZ and tidal oscillation. ► Dissolved Mo peaks were attributed to direct inputs from the Bordeaux agglomeration.
[show abstract][hide abstract] ABSTRACT: Based on high spatial resolution monitoring, the first spatial distribution maps for the eight trace elements identified as priority contaminants in aquatic systems (i.e. As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in surface sediments of the Gironde Estuary (SW France) are presented. This large European fluvial–estuarine system is known for important historical multi-element (mainly Cd, Zn, Cu and Pb) pollution by former mining and mineral processing activation in the Riou-Mort watershed located 350km upstream the estuary. As a consequence, oyster production in the estuary is prohibited, and Cd concentrations in oysters from the Marennes-Oléron area are close to consumption thresholds. Surface sediment samples were analysed for grain size, particulate organic C and trace element concentrations. Determination of trace elements was carried out by ICP-MS for As, Cd, Cr, Cu, Ni, Pb, Th and Zn, and by CV-AAS for Hg. Total and potentially released trace element stocks in the surface sediment were evaluated by using concentrations in the estuary and in selected sediment core. Assuming that sediment resuspension affects mainly the uppermost sediment layer, the total trace element stocks in the studied 0–10cm depth range may represent the equivalent of one (Cd) to eight (As, Cr) times the annual fluvial trace element inputs into the estuary. Comparing total trace element concentrations in surface sediment with: (i) data on the regional geochemical baseline to evaluate the potentially remobilised fraction and (ii) the potentially bioavailable fraction aimed at establishing a first spatially resolved risk assessment of the trace element “cocktail” present in these sediments at the estuary scale. After correction for grain size effects by Th normalisation, potentially highly toxic metals such as Cd and Hg showed the highest enrichment factors. From ecotoxicological indices, areas were identified and quantified where trace element levels and mobility may bear a risk to benthic organisms. The GIS-based spatial distribution of ecotoxicological indices for the trace element “cocktail” suggests that ∼95% of the surface sediment are ‘Low–Medium’-priority zones, highlighting the need for further impact studies. The produced maps of trace element distributions and associated risk potentials are likely to be a useful tool to authorities in charge of sustainable estuarine management, e.g. for the optimisation of dredging activities or development of the estuarine infrastructure.
[show abstract][hide abstract] ABSTRACT: Laboratory experiments using stable Cd isotopes ((110)Cd and (112)Cd) were conducted to separately and simultaneously characterize Cd accumulation in different tissues of Pacific oysters (Crassostrea gigas) via the (i) trophic and (ii) direct pathways. For this, we exposed juvenile oysters to (110)Cd-spiked seawater ((110)Cd: 2 μg l(-1); constant level) and (112)Cd-spiked food (Thalassiossera weissflogii, (112)Cd: 2 μg l(-1) in 35×10(3) cells/oyster/L) in four experimental treatment groups, each containing 6 oysters, for 21 days with constant trophic feeding. These Cd contamination levels were ∼10 times lower than those typically used in experimental accumulation studies. Three oysters per treatment group were dissected every 7 days with separate sampling of the gills, digestive gland and the rest of the body. Metallothioneins were analysed in the digestive gland and gills. Cadmium concentrations and isotope ratios were measured in water (daily) and tissues (weekly) by GF-AAS and ICP-MS. The observed time-dependant evolution in Cd concentrations and (110)Cd/(114)Cd and (112)Cd/(114)Cd isotope ratios clearly revealed the bio-accumulation short-term kinetics and pathways of Cd contamination in the different tissues. Under the experimental conditions, significantly changed isotope ratios in gills and the digestive gland of oysters suggested rapid and efficient contamination by (110)Cd derived from direct exposure followed by internal Cd transfer between organs. Trophic contamination became measurable after 14 days of exposure corresponding to a trophic transfer rate of 1%. Constant metallothionein levels during the experiment suggested that the initially present metallothionein levels were sufficient to deal with the experimental Cd exposure.
Ecotoxicology and Environmental Safety 10/2010; 74(4):600-6. · 2.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Diagenetic behaviour of mercury species in surface sediments of the highly turbid Gironde Estuary was investigated along 6 vertical profiles, including the water–sediment interface (SWI) in dredged and non-dredged zones. Sediment and pore water were collected for analyses of major redox parameters (e.g. dissolved Fe, Mn and sulphate), dissolved and particulate mono-methyl mercury (MeHg) and divalent mercury (Hg(II)). Concentrations of the dissolved Hg species were clearly (up to 70 times) higher in pore water than in the overlying water column, probably due to the dissolution or degradation of major Hg carrier phases such as Fe oxyhydroxides and particulate organic matter. The different profiles showed maximum MeHgD concentrations (up to 10 pmol L−1) and MeHgD/HgD ratios (up to 40%) at a few cm below the SWI, suggesting intense in situ methylation processes for this zone. Depth-related methylation potential was investigated by spiking the cores with 199Hg(II) and their subsequent incubation. Methylation of isotopically labelled 199Hg(II) was measurable in all cores, suggesting that methylation in the studied sediments was efficient in the uppermost ∼20 cm below the SWI. The comparison between sediments retrieved inside and outside the navigation channel showed higher methylation potential in dredged sediments and in intertidal sediment, suggesting stimulation of the bacterial activity either by inputs (e.g. fresh organic matter, sulphate) due to pore water renewal or by redox oscillation.The estimated MeHgD sediment-to-water flux was greater in non-dredged sediments, probably due to favourable anoxic conditions at the SWI. At the whole estuary scale, the estimated direct sediment to water transfer via passive diffusion was 1.1–2.7 mol yr−1 (210–55 g yr−1) for MeHgD and 3.8–4.0 mol yr−1 (750–790 g yr−1) for Hg(II)D, which is roughly equivalent to 15–50% and <3–12% of the respective annual fluvial gross inputs. The estimated dredging-related transfer of pore water Hg species to the water column appeared negligible (∼0.02 mol yr−1 (3.1 g yr−1) for MeHgD and ∼0.2 mol yr−1 (41 g yr−1) for Hg(II)D). Further work should aim at understanding the impact of suspending dredged anoxic sediments in the water column on the estuarine Hg cycle.
Estuarine Coastal and Shelf Science 01/2010; · 2.32 Impact Factor
[show abstract][hide abstract] ABSTRACT: Variations in sediment total mercury (Hg) concentrations and Hg stable isotopic compositions were investigated in the vicinity of two former non-ferrous metal (zinc) refineries in Lommel (Kempen, Belgium) and Viviez (Aveyron, France). Contaminated Kempen sediment Hg levels are up to 6.8mgkg−1 corresponding to a peak in atmospheric Hg deposition of ~1.0mgm−2year−1 for the year 1968. Atmospheric and riverine Hg contamination from the zinc refinery point sources in Belgium and France present mass dependent (δ202Hg of −0.32 to +0.71‰) and small mass independent Hg isotope signatures (Δ199Hg of −0.15 to −0.04‰) that are significantly different from local geochemical background Hg (δ202Hg of −1.44 to −0.75‰; Δ199Hg of −0.35 to +0.06‰). In addition we found that selected sphalerite (ZnS) ore concentrates carry average δ202Hg of −0.65±1.33‰ (2σ, n=4), similar to published Hg minerals (mainly HgS) with δ202Hg of −0.64±1.82‰ (2σ, n=125). Congolese ZnS ores from the Kipushi deposit show significant mass independent Hg isotope fractionation with average Δ201Hg of −0.09±0.02‰, and Δ199Hg of −0.08±0.01‰ (2σ, n=3), possibly suggesting a partial atmospheric origin for trace Hg within the Kipushi ore deposit. Similar to Zn and Cd isotopes, high temperature non-ferrous metal refining processes appear to preferentially retain the heavy Hg isotopes in slag residues: Hg contaminated Cajarc (France) river sediment δ202Hg values of +0.22±0.52‰ (2σ, n=17), considered to present an integrated picture of post-WWII 20th century slag tailing effluents, are significantly enriched in the heavier Hg isotopes relative to Kempen core B1 atmospheric Hg deposition with δ202Hg of −0.07±0.34‰ (2σ, n=10), as well as relative to Hg containing sulfide minerals with δ202Hg of −0.64±1.82‰ (2σ, n=125). The distinct Hg isotope signatures of natural and anthropogenic Hg suggest that tracing the various Hg emissions into regional Belgian and French ecosystems should be feasible. The highly elevated contamination of Hg in the Kempen warrants further study of local ecosystems including human exposure.
Chemical Geology - CHEM GEOL. 01/2010; 279(3):90-100.
[show abstract][hide abstract] ABSTRACT: Mining/smelting wastes and reservoir sediment cores from the Lot River watershed were studied using mineralogical (XRD, SEM–EDS, EMPA) and geochemical (redox dynamics, selective extractions) approaches to characterize the main carrier phases of trace metals. These two approaches permitted determining the role of post-depositional redistribution processes in sediments and their effects on the fate and mobility of trace metals. The mining/smelting wastes showed heterogeneous mineral compositions with highly variable contents of trace metals. The main trace metal-bearing phases include spinels affected by secondary processes, silicates and sulfates. The results indicate a clear change in the chemical partitioning of trace metals between the reservoir sediments upstream and downstream of the mining/smelting activities, with the downstream sediments showing a 2-fold to 5-fold greater contribution of the oxidizable fraction. This increase was ascribed to stronger post-depositional redistribution of trace metals related to intense early diagenetic processes, including dissolution of trace metal-bearing phases and precipitation of authigenic sulfide phases through organic matter (OM) mineralization. This redistribution is due to high inputs (derived from mining/smelting waste weathering) at the water–sediment interface of (i) dissolved SO4 promoting more efficient OM mineralization, and (ii) highly reactive trace metal-bearing particles. As a result, the main trace metal-bearing phases in the downstream sediments are represented by Zn- and Fe-sulfides, with minor occurrence of detrital zincian spinels, sulfates and Fe-oxyhydroxides. Sequestration of trace metals in sulfides at depth in reservoir sediments does not represent long term sequestration owing to possible resuspension of anoxic sediments by natural (floods) and/or anthropogenic (dredging, dam flush) events that might promote trace metal mobilization through sulfide oxidation. It is estimated that, during a major flood event, about 870 t of Zn, 18 t of Cd, 25 t of Pb and 17 t of Cu could be mobilized from the downstream reservoir sediments along the Lot River by resuspension-induced oxidation of sulfide phases. These amounts are equivalent to 13-fold (Cd), ∼6-fold (Zn), 4-fold (Pb) the mean annual inputs of the respective dissolved trace metals into the Gironde estuary.