title: Seasonal variations and annual fluxes of arsenic in the Garonne, Dordogne and Isle Rivers, France.
abstract: Daily measurements of water discharges and suspended particulate matter (SPM) concentrations and monthly analyses for arsenic were conducted from 1999 to 2005 on the Garonne, Dordogne and Isle Rivers, the three main tributaries of the Gironde Estuary, France. Despite the known historical polymetallic pollution affecting the Lot-Garonne River system, the highest As concentration level was observed in the Isle River. This was explained by the geological context and various Au/As deposits in this watershed. In the three studied rivers, dissolved As concentrations showed important seasonal variations with maximum values in summer. The dissolved As concentrations were closely related to water temperature and their increase in spring/summer appeared to be induced by water temperatures above approximately 15 degrees C, independently from discharge. The reduction of As(V) to more soluble As(III) and/or destruction of solid As carrier phases by micro-organisms could explain this observation, suggesting that temperature-dependent biogeochemical processes play an important role in controlling As partition and speciation in fluvial systems. Water and SPM fluxes in the Garonne River mainly control arsenic inputs into the Gironde Estuary and the downstream coastal zones. Based on the present data, we propose an empirical model to roughly estimate the annual dissolved and particulate As fluxes in the Garonne, Dordogne and Isle Rivers from annual water and SPM fluxes. The comparison of observed As fluxes and those estimated from the empirical model suggests that resuspension of historical, polluted reservoir sediments during a major flood accounted for approximately 50% of the annual As fluxes in 2003.
authors.affiliation: Université Bordeaux 1, UMR CNRS 5805 EPOC, TGM (Traceurs Géochimiques et Minéralogiques), Av. des Facultés, 33405 Talence Cedex, France.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Masson
authors.forename: Jörg
authors.initials: J
authors.lastname: Schäfer
authors.forename: Gérard
authors.initials: G
authors.lastname: Blanc
authors.forename: Anschutz
authors.initials: A
authors.lastname: Pierre
mesh_terms: D001151:Arsenic / Q000032:analysis*; D004784:Environmental Monitoring; D005602:France; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D001151:Arsenic