The Carnoules mine. Generation of As-rich acid mine drainage, natural attenuation processes and solutions for passive in-situ remediation

7 pagesThe former Carnoules Pb-Zn mine (Department of Gard, France) has produced 1.5 Mt of solid waste containing pyrite and associated metals and metalloids including arsenic and thallium. The tailings are stored behind a dam. Upon oxidation they generate acid (pH≤3) water containing up to 350mg/l of arsenic, 750 to 2700mg/L of iron, sulphate (2000-7500mg/L) and a few mg/L of heavy metals (Pb, Zn, Cd). The water surges at the bottom of the dam forming the Reigous Creek. For the last ten years, the physicochemical, biological, mineralogical and hydrological characteristics of the site have been monitored by the Hydrosciences laboratory with the aim of understanding the processes responsible for the release of pollutants in the tailing stock and of reducing pollution in the mining creek. The results of this study indicate that, unlike at other sites, pyrite oxidation takes place at the bottom of the tailing stock at the entry of oxygenated underground water. The bacterial populations that are present in the tailings and may catalyse the oxidation reactions were identified. About 20 to 30% of the arsenic initially present in the spring water in the form of As(III), precipitates with Fe in less than 30 meters. This leads to the formation of ochre precipitates containing 20% of arsenic around bacterial structures. Several organisms (bacteria and euglena) that mediate Fe and As oxidation in the creek and thus contribute to accelerating arsenic retention in the solid phase were identified. On the basis of these results and pilot plant experiments, solutions for passive in-situ bioremediation are proposed

Sedimentary record of V, U, Mo and Mn in the Pierre-Blanche lagoon (Southern France). Evidence for a major anoxia event during the Roman period

International audienceThe distribution of redox-sensitive elements (V, U, Mo, Mn) was studied in a sedimentary archive of the Pierre-Blanche lagoon encompassing 3500 years of sedimentation. Between 240 and 255 cm (i.e. between 0 and 350 cal. ad) in the core, there was a dark layer with no mollusc shells. Enrichments of V, U and Mo and depletion of Mn were observed in this layer compared with overlying and underlying sediments. This was attributed to the occurrence of anoxia in bottom water or at the sediment/water interface during the Roman period. This episode was concomitant with the formation of a sandy barrier, which now isolates the lagoon from the sea. Our results suggest that the isolation of the lagoon, which was deeper in the period concerned than at present, favoured stagnation of the water. Combined with the excess nutrient inputs because of human activities in Lattara harbour, stagnation may have caused anoxia in bottom water at least in some parts of the Palavasian lagoon system. Bottom conditions nevertheless remained sufficiently reducing for the accumulation of U and Mo to persist until around 800 cal. ad. Although the lagoon has been hyper-eutrophic since at least the middle of the 20th century and although anoxia occurs frequently in summer, redox proxies show no evidence for their occurrence. The shallow water and associated resuspension and reoxidation events explain the lack of V, Mo and U enrichment in recent sediments

A 3500-Year Record of Hg and Pb Contamination in a mediterranean Sedimentary Archive (The Pierre Blanche Lagoon, France)

International audienceA sediment core encompassing 3500 years of continuous sedimentation has been collected from a coastal lagoon located on the southwestern French Mediterranean coast. Lead concentrations and stable isotopes show that the sediments have recorded the three major periods of Pb pollution: the Etruscan-Greek-Roman period (650 BC to AD 50), the medieval period (AD 650 to AD 1450), and the modern period (from around AD 1850 to the present). These periods were separated by low pollution periods during the Dark Ages (between AD 50 and 650) and during the 16th century. From the end of the 19th century to the 1960s, Pb pollution increased exponentially. Coal combustion was the major source of Pb in the lagoon in the second half of the 20th century. Both the decrease in coal consumption and the ban on leaded gasoline resulted in a decrease in Pb pollution by a factor of 1.5 between 1973 and 1995. From 1991, sewage treatment plants and incinerators could be the major source of Pb. The average baseline Hg concentration from 1525 BC to AD 900 was 0.017 ± 0.003 μg g(-1) (n = 54). The Hg concentrations profile shows three major peaks: in AD 1150, AD 1660, and AD 1969, with the concentrations being respectively 8, 5, and 34 times higher than the baseline levels. The medieval peak (AD 1150) is attributed the medical use of Hg in the town of Montpellier and/or the burning of soil and vegetation. Noticeable Hg pollution was also detected during the 17th century in relation to gold and silver amalgamation in Europe. From the end of the 19th century, Hg concentrations increased exponentially until 1969. This modern pollution is attributed to the burning of coal

Variabilité à court terme des concentrations en éléments trace dissous dans la Marne et la Seine près de Paris.

International audienceThe concentrations of dissolved trace elements (Li, B, Mn, Cu, As, Rb, Sr, Mo, Cd, Ba, Pb) in the Marne and Seine rivers in the Paris urban area were monitored over a 2-year period. The resulting data indicated moderate contamination of waters by the most toxic elements (Cu, As, Cd and Pb). The River Marne upstream and the River Seine downstream of the city of Paris displayed similar concentrations. However higher fluxes of trace elements were observed in the Seine than in the Marne due to their different discharges. Li, B, Rb, Sr and Ba concentrations were correlated with river discharge and concentrations were higher during high river flow. This was interpreted as a dilution by discharge from a major natural or anthropogenic source. Mn, Cu, Mo, Cd and Pb concentrations were not correlated with discharge. Dissolved Mn, Cu and Cd increased rapidly in summer, whereas the concentration of Mo decreased. These dariations were attributed to redox processes. During summer when the dissolved oxygen concentrations decrease, Mn, Cu, Cd and Pb are released into solution whereas Mo is immobilised. Like metals, variations in arsenic contents were not linked with discharge. Its similarity with phosphate distribution suggests similar controls involving phytoplankton uptake and release from sediments through organic matter mineralization

Organotins in a medium-size Mediterranean basin (the Herault River)

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Deciphering As and Cu cycling in sediment pore waters in a large marina (Port Camargue, southern France) using a multi-tracer (Fe, Mn, U, Mo) approach

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Variation of dissolved and particulate metal(loid) (As, Cd, Pb, Sb, Tl, Zn) concentrations under varying discharge during a Mediterranean flood in a former mining watershed, the Gardon River (France)

International audienceThe variation of dissolved and particulate metal(loid) concentrations was investigated during a Mediterranean flood in a former mining watershed, the Gardon River (SE France), using high-temporal resolution sampling. Dissolved antimony originating from the Upper Gardon River watershed underwent dilution during flood. Conversely, dissolved As and particulate As, Pb, Zn, Cd and Tl concentrations exhibited increased values during rising flood compared to low and receding flow conditions, with a double-peak shape. As, Pb, Cd and Tl concentration data in suspended particulate matter from this double-peak were distributed along two different correlation lines, showing the successive mobilization of two groups of particles highly enriched with As and Cd or Pb and Tl, both inherited from ancient Pb/Zn mines. Metal(loid) loads during the monitored 24h-flood event were: 0.5kg for Cd, 19.4kg for Sb and 204kg for As in the dissolved phase and 24kg for Cd, 38kg for Tl, 94kg for Sb, 1915kg for As, 2860kg for Pb and 5214kg for Zn in the particulate phase. Altogether, these results highlighted the importance of floods in the mobilization of metals and metalloids from ancient mining sites in Mediterranean regions, showing the need for high-temporal resolution monitoring of flood events to accurately assess the long-term contribution of mining activity to metal(loid) loads of downstream watershed

Behaviour of butyltin compounds in the sediment pore waters of a contaminated marina (Port Camargue, South of France)

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Assessment of copper bioavailability in vineyard runoff waters by DPASV and algal bioassay

Corresponding author. fax: +33 467 548 695. E-mail address: [email protected] (E. Gomez).International audienceThe aim of this study was to assess the toxicity of runoff waters in an agricultural multipollution context through an in-depth assessment of copper bioavailability and toxicity. Runoff waters were screened for major ions, metals and diuron. The potential environmental impact of these runoff waters was evaluated using the conventional 72-h growth inhibition test with the green alga Pseudokirchneriella subcapitata. The results suggested that the toxicity detected in the calcareous vineyard field was due to the presence of diuron, whereas the non-calcareous runoff waters were non-toxic. Chemical speciation modelling by MINEQL revealed that most of the copper present in the non-toxic natural runoff waters was complexed by organic matter. These samples were spiked with copper, and then the toxicity and the electrochemically bioavailable copper fraction were measured. Differential pulse anodic stripping voltammetry (DPASV) was used to detect labile complexes and free copper. This combined approach highlighted the presence of some labile copper complexes in samples reaching the EC10—these could have contributed to the copper toxicit