Archaeal diversity: temporal variation in the arsenic-rich creek sediments of Carnoulès Mine, France.

The Carnoulès mine is an extreme environment located in the South of France. It is an unusual ecosystem due to its acidic pH (2-3), high concentration of heavy metals, iron, and sulfate, but mainly due to its very high concentration of arsenic (up to 10 g L⁻¹ in the tailing stock pore water, and 100-350 mg L⁻¹ in Reigous Creek, which collects the acid mine drainage). Here, we present a survey of the archaeal community in the sediment and its temporal variation using a culture-independent approach by cloning of 16S rRNA encoding genes. The taxonomic affiliation of Archaea showed a low degree of biodiversity with two different phyla: Euryarchaeota and Thaumarchaeota. The archaeal community varied in composition and richness throughout the sampling campaigns. Many sequences were phylogenetically related to the order Thermoplasmatales represented by aerobic or facultatively anaerobic, thermoacidophilic autotrophic or heterotrophic organisms like the organotrophic genus Thermogymnomonas. Some members of Thermoplasmatales can also derive energy from sulfur/iron oxidation or reduction. We also found microorganisms affiliated with methanogenic Archaea (Methanomassiliicoccus luminyensis), which are involved in the carbon cycle. Some sequences affiliated with ammonia oxidizers, involved in the first and rate-limiting step in nitrification, a key process in the nitrogen cycle were also observed, including Candidatus Nitrososphaera viennensis and Candidatus nitrosopumilus sp. These results suggest that Archaea may be important players in the Reigous sediments through their participation in the biochemical cycles of elements, including those of carbon and nitrogen.

A 3500-year record of Hg and Pb contamination in a mediterranean sedimentary archive (the Pierre Blanche Lagoon, France).

A 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.

A new bacterial strain mediating As oxidation in the Fe-rich biofilm naturally growing in a groundwater Fe treatment pilot unit.

A bacterial strain B2 that oxidizes arsenite into arsenate was isolated from the biofilm growing in a biological groundwater treatment process used for Fe removal. This strain is phylogenetically and morphologically different from the genus Leptothrix commonly encountered in biological iron oxidation processes. T-RFLP fingerprint of the biofilm revealed that this isolated strain B2 corresponds to the major population of the bacterial community in the biofilm. Therefore, it is probably one of the major contributors to arsenic removal in the treatment process.

Sorption and redox processes controlling arsenic fate and transport in a stream impacted by acid mine drainage.

Reigous acid creek originating from the Carnoulès tailings impoundment supplies high concentrations of arsenic under soluble (up to approximately 4 mg/l) and particulate (up to 150 mgAs/g) phases to the Amous river, situated at the drainage basin of the Rhône river (Southern France). The metalloid is present as As(III) (>95%) in Reigous creek water while As(V) predominates (50-80%) in the solid phase, i.e. schwertmannite. At the confluence between acid (pH<5) creek and alkaline Amous river, As(III) concentrations decrease ten-fold through dilution and formation of As-rich ferrihydrite (As/Fe=0.02-0.1) containing 10-30% As(III). However, these attenuation processes are not efficient in the summer heatwave of 2003 since As concentrations in Amous river water (>or=20 microg/l) and As/Fe ratios in particulate matter (>or=0.07) are closed to those of Reigous creek (

A reassessment of trace metal budgets in the Western Mediterranean Sea.

This paper presents inputs and output fluxes of dissolved metals (As, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn) into and out the Western Mediterranean. These flux estimates are based on the most recently published concentrations and fluxes for the atmosphere, the rivers and the straits. Comparison of the different sources shows the predominance of the inputs through the straits over other sources. The river input is smaller than the atmospheric input except for As. For all elements except Fe, output flux and input flux are balanced; iron budget indicates transfer from the dissolved to the particulate phase.

Positive gadolinium anomalies in wastewater treatment plant effluents and aquatic environment in the Hérault watershed (South France).

Anthropogenic gadolinium (Gd), used as a contrast agent in magnetic resonance imaging, may enter rivers and groundwaters with the effluents of wastewater treatment plant (WWTP). Such contaminations, which are mainly found in densely populated areas with highly developed medical systems, induce positive gadolinium anomalies in waters. This study reports on the occurrence of positive Gd anomaly in wastewaters, surface and groundwaters in a slightly populated Mediterranean watershed. Water samples have been collected along the Hérault River, in its tributaries, in wells and springs supplying drinking water and in WWTP effluents during two sampling campaigns in February and July 2003. Systematically pronounced positive gadolinium anomalies (Gd/Gd( *)) were observed in WWTP effluents with values reaching 306. These observations have shown that Gd/Gd( *) can also be found in wastewater drained from rural communities, not equipped with MRI facilities. Positive gadolinium anomalies were detected in two tributaries of the Hérault River and in some wells supplying drinking water, corresponding to an excess of anthropogenic Gd in water up to 15.4pM. A monthly monitoring on one well has confirmed the persistence of gadolinium anomalies all along the year, suggesting a continual wastewater contamination on this site. A spatial monitoring on one tributary showed that wastewater contribution modifies completely the normalized REE pattern of river water, resulting in a decrease of REE amount correlated to the Gd anomaly appearance.

Inorganic arsenic speciation at river basin scales: the Tinto and Odiel rivers in the Iberian Pyrite Belt, SW Spain.

The Tinto and Odiel rivers are heavily affected by acid mine drainage from mining areas in the Iberian Pyrite Belt. In this work we have conducted a study along these rivers where surface water samples have been collected. Field measurements, total dissolved metals and Fe and inorganic As speciation analysis were performed. The average total concentration of As in the Tinto river (1975 microg L(-1)) is larger than in the Odiel river (441 microg L(-1)); however, the mean concentration of As(III) is almost four times higher in the Odiel. In wet seasons the mean pH levels of both rivers (2.4 and 3.2 for the Tinto and Odiel, respectively) increase slightly and the amount of dissolved total arsenic tend to decrease, while the As(III)/(V) ratio strongly increase. Besides, the concentration of the reduced As species increase along the water course. As a result, As(III)/(V) ratio can be up to 100 times higher in the lower part of the basins. An estimation of the As(III) load transported by both rivers into the Atlantic Ocean has been performed, resulting in about 60 kg yr(-1) and 2.7t yr(-1) by the Tinto and Odiel rivers, respectively.

Archaeal diversity in a Fe-As rich acid mine drainage at Carnoulès (France).

The acid waters (pH=2.73-3.4) that originate from the Carnoulès mine tailings (France) are known for their very high concentrations of As (up to 10,000 mg l(-1)) and Fe (up to 20,000 mg l(-1)). To analyze the composition of the archaeal community, (their temporal variation inside the tailing and spatial variations all along the Reigous Creek, which drains the site), seven 16S rRNA gene libraries were constructed. Clone analysis revealed that all the sequences were affiliated to the phylum Euryarchaeota, while Crenarchaeota were not represented. The study showed that the structure of the archaeal community of the aquifer of the tailing stock is different to that of the Reigous Creek. Irrespective of the time of sampling, the most abundant sequences found inside the tailing stock were related to Ferroplasma acidiphilum, an acidophilic and ferrous-iron oxidizing Archaea well known for its role in bioleaching. Inversely, in Reigous Creek, a sequence affiliated to the uncultured Thermoplasmatales archaeon, clone YAC1, was largely dominant. This study provides a better understanding of the microbial community associated with an acid mine drainage rich in arsenic.

Diversity of microorganisms in Fe-As-rich acid mine drainage waters of Carnoulès, France.

The acid waters (pH 2.7 to 3.4) originating from the Carnoulès mine tailings contain high concentrations of dissolved arsenic (80 to 350 mg.liter(-1)), iron (750 to 2,700 mg.liter(-1)), and sulfate (2,000 to 7,500 mg.liter(-1)). During the first 30 m of downflow in Reigous creek issuing from the mine tailings, 20 to 60% of the dissolved arsenic is removed by coprecipitation with Fe(III). The microbial communities along the creek have been characterized using terminal-restriction fragment length polymorphism (T-RFLP) and 16S rRNA gene library analyses. The results indicate a low bacterial diversity in comparison with unpolluted water. Eighty percent of the sequences obtained are related to sequences from uncultured, newly described organisms or recently associated with acid mine drainage. As expected owing to the water chemistry, the sequences recovered are mainly related to bacteria involved in the geochemical Fe and S cycles. Among them, sequences related to uncultured TrefC4 affiliated with Gallionella ferruginea, a neutrophilic Fe-oxidizing bacterium, are dominant. The description of the bacterial community structure and its dynamics lead to a better understanding of the natural remediation processes occurring at this site.

Immobilization of arsenite and ferric iron by Acidithiobacillus ferrooxidans and its relevance to acid mine drainage.

Weathering of the As-rich pyrite-rich tailings of the abandoned mining site of Carnoulès (southeastern France) results in the formation of acid waters heavily loaded with arsenic. Dissolved arsenic present in the seepage waters precipitates within a few meters from the bottom of the tailing dam in the presence of microorganisms. An Acidithiobacillus ferrooxidans strain, referred to as CC1, was isolated from the effluents. This strain was able to remove arsenic from a defined synthetic medium only when grown on ferrous iron. This A. ferrooxidans strain did not oxidize arsenite to arsenate directly or indirectly. Strain CC1 precipitated arsenic unexpectedly as arsenite but not arsenate, with ferric iron produced by its energy metabolism. Furthermore, arsenite was almost not found adsorbed on jarosite but associated with a poorly ordered schwertmannite. Arsenate is known to efficiently precipitate with ferric iron and sulfate in the form of more or less ordered schwertmannite, depending on the sulfur-to-arsenic ratio. Our data demonstrate that the coprecipitation of arsenite with schwertmannite also appears as a potential mechanism of arsenite removal in heavily contaminated acid waters. The removal of arsenite by coprecipitation with ferric iron appears to be a common property of the A. ferrooxidans species, as such a feature was observed with one private and three collection strains, one of which was the type strain.

Mediation of arsenic oxidation by Thiomonas sp. in acid-mine drainage (Carnoulès, France).

AIMS: To isolate, identify, and characterize heterotrophic bacteria in acid-mine drainage that mediate oxidation of As(III). METHODS AND RESULTS: Samples of acid-mine drainage were collected over a period of 14 months. Heterotrophic and non-obligatory acidophilic bacteria in the samples were cultured on a solid medium (pH 7.0-7.2), and three strains were isolated. The three different strains belong to the genus Thiomonas, and have more than 99% homology with the group Ynys1. Culturing in mineral media demonstrated that the isolated strains used thiosulphate as an energy source, and oxidized iron in the presence of thiosulphate. However, none of the strains were able to oxidize arsenic in the presence of thiosulphate, nor could they use iron or arsenic alone as an energy source. In vitro experiments demonstrated that two of the Thiomonas strains were able to oxidize more than 90% of the As(III) present in the acid-mine drainage, whereas no abiotic oxidation of arsenic occurred. CONCLUSIONS: Two strains of newly identified Thiomonas sp. found in acid-mine drainage are capable of oxidizing arsenic. SIGNIFICANCE AND IMPACT OF STUDY: These results represent the first reported oxidation of arsenic by Thiomonas sp. Biologically mediated oxidation and subsequent immobilization of arsenic is of great interest for the remediation of contaminated mine sites.