title: Origin, mobility, and temporal evolution of arsenic from a low-contamination catchment in Alpine crystalline rocks.
abstract: The reduction to 10 μg/l of the limit for arsenic in drinking water led many resource managers to deal with expensive treatments. In the very common case of arsenic levels close to the recommended maximum concentration, knowing the origin and temporal evolution of As has become of great importance. Here we present a case study from an alpine basin. Arsenic speciation, isotopic compositions of pyrite, sulfate and water, and concentrations of major and trace elements demonstrate a geogenic source for arsenic linked to the dissolution of pyrite. We provide new tools to further study As at low concentrations where many processes may be masked. The observed negative correlation between δ(34)SSO4 and [As] is interpreted as a Rayleigh-type sulfur-isotope fractionation during increasing pyrite dissolution. The observed positive correlation between δ(18)OSO4 and As(V)/As(III) could help to retrieve initial redox conditions. A 3-year long monitoring at high-resolution demonstrated that drought conditions enhance pyrite dissolution whose degradation products are scavenged by recharge water. An increase in As in groundwater may result from droughts due to enhanced oxygen entry in the unsaturated zone. The 2003 European heatwave had a major effect.
authors: CEA, DAM, DIF, F-91297 Arpajon, France; Institut de Physique du Globe de Paris-Sorbonne Paris Cité, CNRS, Université Paris Diderot, 1 rue Jussieu, F-75238 Paris cedex 05, France. Electronic address: Eric.Pili@cea.fr.
authors: Eric
authors: E
authors: Pili
authors: Delphine
authors: D
authors: Tisserand
authors: Sarah
authors: S
authors: Bureau
mesh_terms: D001151:Arsenic / Q000737:chemistry*; D004784:Environmental Monitoring / Q000379:methods; D005060:Europe; D005602:France; D005843:Geography; D060587:Groundwater; D007501:Iron / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D045483:Rivers; D013431:Sulfates / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry; D013460:Sulfur Isotopes / Q000737:chemistry; D013997:Time Factors; D014131:Trace Elements / Q000032:analysis; D014867:Water / Q000737:chemistry; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000737:chemistry; D014881:Water Supply
chemical_list: D013431:Sulfates; D013440:Sulfides; D013460:Sulfur Isotopes; D014131:Trace Elements; D014874:Water Pollutants, Chemical; D014867:Water; C011342:pyrite; D013455:Sulfur; D007501:Iron; D001151:Arsenic; D010100:Oxygen