title: Effect of water table variations and input of natural organic matter on the cycles of C and N, and mobility of As, Zn and Cu from a soil impacted by the burning of chemical warfare agents: A mesocosm study.
abstract: A mesocosm study was conducted to assess the impact of water saturation episodes and of the input of bioavailable organic matter on the biogeochemical cycles of C and N, and on the behavior of metal(loid)s in a soil highly contaminated by the destruction of arsenical shells. An instrumented mesocosm was filled with contaminated soil taken from the "Place-à-Gaz" site. Four cycles of dry and wet periods of about one month were simulated for 276days. After two dry/wet cycles, organic litter sampled on the site was added above the topsoil. The nitrogen cycle was the most impacted by the wet/dry cycles, as evidenced by a denitrification microbial process in the saturated level. The concentrations of the two most mobile pollutants, Zn and As, in the soil water and in the mesocosm leachate were, respectively, in the 0.3-1.6mM and 20-110μM ranges. After 8months of experiment, about 83g·m-3of Zn and 3.5g·m-3of As were leached from the soil. These important quantities represent <1% of the solid stock of this contaminant. Dry/wet cycles had no major effect on Zn mobility. However, soil saturation induced the immobilization of As by trapping As V but enhanced As III mobility. These phenomena were amplified by the presence of bioavailable organic matter. The study showed that the natural deposition of forest organic litter allowed a part of the soil's biological function to be restored but did not immobilize all the Zn and As, and even contributed to transport of As III to the surrounding environment. The main hazard of this type of site, contaminated by organo-arsenic chemical weapons, is the constitution of a stock of As that may leach into the surrounding environment for several hundred years.
authors.affiliation: BRGM, 3 Avenue Claude Guillemin, 45060 Orléans, France; Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; CNRS, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France. Electronic address: h.thouin@brgm.fr.
authors.forename: Hugues
authors.initials: H
authors.lastname: Thouin
authors.affiliation: BRGM, 3 Avenue Claude Guillemin, 45060 Orléans, France; Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; CNRS, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Battaglia-Brunet
authors.affiliation: Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; CNRS, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Gautret
authors.affiliation: Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; CNRS, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France.
authors.forename: Lydie
authors.initials: L
authors.lastname: Le Forestier
authors.affiliation: BRGM, 3 Avenue Claude Guillemin, 45060 Orléans, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Breeze
authors.affiliation: UT2A, Hélioparc Pau Pyrénées, 2 avenue du président Angot, 64053 Pau, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Séby
authors.affiliation: Université d'Orléans, ISTO, UMR 7327, 45071 Orléans, France; CNRS, ISTO, UMR 7327, 45071 Orléans, France; BRGM, ISTO, UMR 7327, BP 36009, 45060 Orléans, France.
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Norini
authors.affiliation: BRGM, 3 Avenue Claude Guillemin, 45060 Orléans, France.
authors.forename: Sebastien
authors.initials: S
authors.lastname: Dupraz
keywords: Arsenic; Mesocosm monitoring; Metals; Nitrogen; Organic matter; Organo-arsenic chemical weapons; Soil saturation