Biological attenuation of arsenic and iron in a continuous flow bioreactor treating acid mine drainage (AMD)

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The impact of increased flooding occurrence on the mobility of potentially toxic elements in floodplain soil – a review

The frequency and duration of flooding events are increasing due to land-use changes increasing run-off of precipitation, and climate change causing more intense rainfall events. Floodplain soils situated downstream of urban or industrial catchments, which were traditionally considered a sink of potentially toxic elements (PTEs) arriving from the river reach, may now become a source of legacy pollution to the surrounding environment if PTEs are mobilised by unprecedented flooding events. When a soil floods, the mobility of PTEs can increase or decrease due to the net effect of five key processes; (i) the soil redox potential decreases which can directly alter the speciation, and hence mobility, of redox sensitive PTEs (e.g. Cr, As), (ii) pH increases which usually decreases the mobility of metal cations (e.g. Cd2+, Cu2+, Ni2+, Pb2+, Zn2+), (iii) dissolved organic matter (DOM) increases, which chelates and mobilises PTEs, (iv) Fe and Mn hydroxides undergo reductive dissolution, releasing adsorbed and co-precipitated PTEs, and (v) sulphate is reduced and PTEs are immobilised due to precipitation of metal sulphides. These factors may be independent mechanisms, but they interact with one another to affect the mobility of PTEs, meaning the effect of flooding on PTE mobility is not easy to predict. Many of the processes involved in mobilising PTEs are microbially mediated, temperature dependent and the kinetics are poorly understood. Soil mineralogy and texture are properties that change spatially and will affect how the mobility of PTEs in a specific soil may be impacted by flooding. As a result, knowledge based on one river catchment may not be particularly useful for predicting the impacts of flooding at another site. This review provides a critical discussion of the mechanisms controlling the mobility of PTEs in floodplain soils. It summarises current understanding, identifies limitations to existing knowledge, and highlights requirements for further research

Etude de la contamination par les métaux et métalloïdes d’origine minière sur le bassin des Gardons : approche élémentaire (As, Cd, Hg, Pb, Sb, Tl, Zn) et isotopique (Sb, Zn)

The overall objective of this thesis was to improve understanding of the influence of former mining sites on metal (Cd, Hg, Tl, Pb, Zn) and metalloid (As, Sb) contamination of the downstream hydrosystem. A special care was given to antimony (Sb), its behavior in mining-impacted streams remains poorly known and its isotopic signature could be usefull to track sources and processes. The study site is the Gardon River watershed in the south-east of France which drains many abandoned mining sites (Pb, Zn, Sb, coal). Metal and metalloid enrichment was studied in current and historical sediments of the Gardon River watershed. A sedimentary archive was used to investigate past metal contamination history. The prevailing metal and metalloid sources in sediments were determined together with the potential mobility of these elements toward the aqueous phase. In addition, dissolved and particulate metal and metalloid concentration variations were studied during a flood event using a high temporal resolution sampling. Altogether, the results suggest that former mining sites of the Gardon River watershed contribute to metal and metalloid enrichment of the downstream hydrosystem, especially during floods. More specifically, antimony behavior was investigated in a tributary of the Gardon River which is impacted by acid mine drainage originating from the disused Carnoulès mine and antimony isotopic composition was determined in waters collected in the Gardon River watershed and in the Upper Orb River after developing a protocol for preconcentrating and purifying Sb. The results highlight the potential of antimony isotopes to track the origin of this element and the processes that it undergoes during its transfer in streams impacted by mine drainage.L'objectif général de cette thèse est de mieux comprendre l'influence d'anciens sites miniers sur la contamination en métaux (Cd, Hg, Tl, Pb, Zn) et métalloïdes (As, Sb) de l'hydrosystème aval. Une attention particulière a été portée à l'antimoine (Sb), dont le comportement dans les cours d'eau contaminés par les drainages miniers reste mal connu et dont la signature isotopique pourrait permettre de tracer différentes sources et processus. Le site d'étude est le bassin des Gardons dans le Gard ; ce cours d'eau Cévenol draine de nombreux sites miniers abandonnés (Pb, Zn, Sb, charbon). L'enrichissement en métaux et métalloïdes a été étudié dans les sédiments actuels et anciens du bassin des Gardons. Un historique de la contamination métallique a été reconstitué à l'aide d'une archive sédimentaire. Les sources prépondérantes de métaux et métalloïdes dans les sédiments ont été déterminées ainsi que la mobilité potentielle de ces éléments vers la phase aqueuse. En complément, les variations de concentrations en métaux et métalloïdes dans les phases dissoute et particulaire ont été étudiées lors d'un épisode de crue grâce à un échantillonnage à haute résolution temporelle. Dans leur ensemble, les résultats montrent que les anciennes mines du bassin des Gardons contribuent à l'enrichissement en métaux et métalloïdes du cours d'eau aval, particulièrement en période de crue. Plus spécifiquement, le comportement de l'antimoine a été étudié dans un affluent du Gardon impacté par du drainage minier acide en aval de l'ancienne mine de Carnoulès et la composition isotopique de l'antimoine a été déterminée dans des eaux prélevées sur le bassin des Gardons et de l'Orb amont, après mise au point d'un protocole de purification/pré-concentration de Sb. Les résultats mettent en évidence le potentiel des isotopes de l'antimoine pour tracer l'origine de cet élément et les processus qu'il subit au cours de son transfert dans les cours d'eau impactés par du drainage de mine

Study of metal and metalloid contamination deriving from mining activities in the Gardon River hydrosytem (SE, France) : elemental (As, Cd, Hg, Pb, Sb, Tl, Zn) and stable isotope geochemistry (Sb, Zn) approache

L'objectif général de cette thèse est de mieux comprendre l'influence d'anciens sites miniers sur la contamination en métaux (Cd, Hg, Tl, Pb, Zn) et métalloïdes (As, Sb) de l'hydrosystème aval. Une attention particulière a été portée à l'antimoine (Sb), dont le comportement dans les cours d'eau contaminés par les drainages miniers reste mal connu et dont la signature isotopique pourrait permettre de tracer différentes sources et processus. Le site d'étude est le bassin des Gardons dans le Gard ; ce cours d'eau Cévenol draine de nombreux sites miniers abandonnés (Pb, Zn, Sb, charbon). L'enrichissement en métaux et métalloïdes a été étudié dans les sédiments actuels et anciens du bassin des Gardons. Un historique de la contamination métallique a été reconstitué à l'aide d'une archive sédimentaire. Les sources prépondérantes de métaux et métalloïdes dans les sédiments ont été déterminées ainsi que la mobilité potentielle de ces éléments vers la phase aqueuse. En complément, les variations de concentrations en métaux et métalloïdes dans les phases dissoute et particulaire ont été étudiées lors d'un épisode de crue grâce à un échantillonnage à haute résolution temporelle. Dans leur ensemble, les résultats montrent que les anciennes mines du bassin des Gardons contribuent à l'enrichissement en métaux et métalloïdes du cours d'eau aval, particulièrement en période de crue. Plus spécifiquement, le comportement de l'antimoine a été étudié dans un affluent du Gardon impacté par du drainage minier acide en aval de l'ancienne mine de Carnoulès et la composition isotopique de l'antimoine a été déterminée dans des eaux prélevées sur le bassin des Gardons et de l'Orb amont, après mise au point d'un protocole de purification/pré-concentration de Sb. Les résultats mettent en évidence le potentiel des isotopes de l'antimoine pour tracer l'origine de cet élément et les processus qu'il subit au cours de son transfert dans les cours d'eau impactés par du drainage de mine.The overall objective of this thesis was to improve understanding of the influence of former mining sites on metal (Cd, Hg, Tl, Pb, Zn) and metalloid (As, Sb) contamination of the downstream hydrosystem. A special care was given to antimony (Sb), its behavior in mining-impacted streams remains poorly known and its isotopic signature could be usefull to track sources and processes. The study site is the Gardon River watershed in the south-east of France which drains many abandoned mining sites (Pb, Zn, Sb, coal). Metal and metalloid enrichment was studied in current and historical sediments of the Gardon River watershed. A sedimentary archive was used to investigate past metal contamination history. The prevailing metal and metalloid sources in sediments were determined together with the potential mobility of these elements toward the aqueous phase. In addition, dissolved and particulate metal and metalloid concentration variations were studied during a flood event using a high temporal resolution sampling. Altogether, the results suggest that former mining sites of the Gardon River watershed contribute to metal and metalloid enrichment of the downstream hydrosystem, especially during floods. More specifically, antimony behavior was investigated in a tributary of the Gardon River which is impacted by acid mine drainage originating from the disused Carnoulès mine and antimony isotopic composition was determined in waters collected in the Gardon River watershed and in the Upper Orb River after developing a protocol for preconcentrating and purifying Sb. The results highlight the potential of antimony isotopes to track the origin of this element and the processes that it undergoes during its transfer in streams impacted by mine drainage

A single-step purification method for the precise determination of the antimony isotopic composition of environmental, geological and biological samples by HG-MC-ICP-MS

International audienceAntimony isotopes have been recently used as geochemical tracers for archeological or environmental purposes. The purification of antimony in samples with a low Sb concentration and a complex matrix is a critical step to measure the 123Sb/121Sb ratio by hydride generation coupled to a multi-collector inductively coupled plasma mass spectrometer (HG-MC-ICP-MS). A single-step purification method based on the use of thiol-functionalized mesoporous silica powder (TSP) was developed to separate antimony from other elements. A low amount of Sb (40–100 ng) is required thanks to low procedural blanks (<1 ng Sb) and an efficient removal (98.7% on average) of potential interfering elements (including As, Cd, Co, Cr, Cu, Fe, Ni, Pb, Se, and Sn). The method was validated on fourteen Certified Reference Materials (CRMs) including environmental materials (sediments and soils), biological materials (plants, human blood and urine), rocks and anthropogenic materials (fly ash, road dust and polyethylene). Antimony was recovered at 100 ± 7% and no isotopic fractionation occurred during the procedure. The isotopic composition of Sb (δ123Sb) in the CRMs ranged between −0.52 ± 0.06‰ (2 sd) and 0.40 ± 0.03‰ (2 sd) relative to an in-house isotopic standard solution (SPEX). The external reproducibility was evaluated at 0.05‰ (2 sd) for δ123Sb, based on replicated measurements of independently digested and purified CRMs. CRMs GSD-3, SDO-1 and BCR-176R exhibited δ123Sb values similar to previous measurements by Rouxel et al. (2003). In addition, three pure standard solutions of Sb were measured against the in-house isotopic standard solution. Two of them were isotopically similar (δ123Sb = 0.00 ± 0.05‰, Sb Fisher Scientific® and PlasmaCAL-1, SCP Science®), while a δ123Sb value of 0.62 ± 0.02‰ was measured for the third one (PlasmaCAL-2, SCP Science®). This raises the importance of choosing a common isotopic standard solution to compare already published and future Sb isotope data

Equilibrium mass-dependent isotope fractionation of antimony between stibnite and Sb secondary minerals: A first-principles study

International audienceAntimony (Sb) isotopes are gaining increasing interest for their potential as geochemical tracers in geological, environmental and archaeological studies. However, little is known about the parameters controlling Sb isotope fractionation, which is essential to interpret variations of isotopic signature in natural systems. In this study, equilibrium mass-dependent isotope fractionation factors (β-factor) were determined between different Sb-bearing minerals commonly found in mining environments including primary Sb sulphide (stibnite Sb 2 S 3) and its oxidation products (valentinite Sb 2 O 3 , senarmontite Sb 2 O 3 , cervantite Sb 2 O 4) and synthetic antimony pentoxide Sb 2 O 5. First-principles calculations within the Density Functional Theory (DFT) were performed with different functionals to test the robustness of the method. Among the studied minerals, stibnite has the lowest β-factor (ln(β) = 0.71 ‰ at 22°C), then β-factors progressively increase from valentinite (ln(β) = 1.64 ‰ at 22 °C), to senarmontite (ln(β) = 1.80 ‰ at 22 °C), cervantite (ln(β) = 2.20 ‰ at 22 °C) and antimony pentoxide (ln(β) = 3.03 ‰ at 22 °C). The parameters that most fractionate Sb isotopes are found to be i) the change of Sb oxidation state (Sb isotope ratio in Sb(V)-bearing minerals is higher than in Sb(III)-bearing minerals), ii) the change of first neighbour of Sb (Sb isotope ratio in Sb-O bonds is higher than in Sb-S bonds) and iii) distortion of the atomic Sb-O polyhedrons. The negligible differences in the β-factors obtained with different functionals showed the robustness of the approach for the calculation of β-factors, despite differences in the calculated mineral lattice and Raman frequencies. The results of this study provide a theoretical basis to interpret natural Sb isotope variations. In sulphide mining environments, the results suggest that a significant enrichment in the heavy isotope could occur during oxidative dissolution of stibnite and subsequent precipitation of Sb(III) and Sb(V) oxides. More generally, this work strongly supports that Sb isotopes may be a useful tracer of Sb transformation processes in nature

Évaluation des sources de contaminants métalliques. OSR4 | Action IV.2

L’OSR s’est intéressé depuis ces débuts aux comportements et flux de divers éléments traces métalliques (ETM) associés aux particules. Les objectifs étaient de caractériser les valeurs actuelles de concentrations et de flux en complétant les suivis de l’Agence de l’Eau RMC, et de préciser autant que possible l’origine des éléments. Pour ceci, les travaux ont porté sur les possibilités d’utiliser les éléments constitutifs des particules pour définir les sources (cf. livrable IV.1), et sur l’utilisation de marqueurs isotopiques de certains ETM. Cette dernière approche a été initiée dans l’OSR 4.Ce document présente les résultats majeurs obtenus à partir de ces différentes approches, et synthétise les documents précédents. La première partie propose une synthèse des apports de l’outil « isotopique ». La deuxième partie présente pour la première fois l’état de la contamination sur le corridor pour huit éléments métalliques et propose des interprétations sur son évolution historique et sur les sources actuelles. Le risque qu’ils peuvent présenter est mis en exergue de valeurs toxicologiques de référence. Les valeurs de flux d’ETM et leurs évolutions sont discutées dans le livrable III.3