title: Sources and historical record of tin and butyl-tin species in a Mediterranean bay (Toulon Bay, France).
abstract: Concentrations of inorganic tin (Sn(inorg)), tributyltin (TBT) and its degradation products dibutyltin (DBT) and monobutyltin (MBT) were measured in surface sediments and in two cores from the Toulon Bay, hosting the major French military harbour. Anticipating planned dredging, the aim of the present work is to map and evaluate for the first time the recent and historic contamination of these sediments by inorganic and organic Sn species derived from antifouling paints used for various naval domains including military, trade, tourism and leisure. Tin and butyl-Sn concentrations in the bay varied strongly (4 orders of magnitude), depending on the site, showing maximum values near the shipyards. The concentrations of total Sn (1.3-112 μg g(-1)), TBT (<0.5-2,700 ng g(-1)), DBT (<0.5-1,800 ng g(-1)) and MBT (0.5-1,000 ng g(-1)) generally decreased towards the open sea, i.e. as a function of both distance from the presumed main source and bottom currents. Progressive degradation state of the butyl-Sn species according to the same spatial scheme and the enrichment factors support the scenario of a strongly polluted bay with exportation of polluted sediment to the open Mediterranean. Low degradation and the historical records of butyl-Sn species in two (210)Pb-dated sediment cores, representative of the Northern Bay, are consistent with the relatively recent use of TBT by military shipyards and confirm maximum pollution during the 1970s, which will persist in the anoxic sediments for several centuries. The results show that (a) degradation kinetics of butyl-Sn species depend on environmental conditions, (b) the final degradation product Sn(inorgBT) is by far the dominant species after 10-12 half-life periods and (c) using recent data to reliably assess former TBT contamination requires the use of a modified butyl-Sn degradation index BDI(mod). Resuspension of extremely contaminated subsurface sediments by the scheduled dredging will probably result in mobilization of important amounts of butyl-Sn species.
authors.affiliation: Université de Bordeaux, UMR 5805 EPOC, CS50023, Av. Geoffroy St. Hilaire, 33615, Pessac Cedex, France.
authors.forename: Frédérique
authors.initials: F
authors.lastname: Pougnet
authors.forename: Jörg
authors.initials: J
authors.lastname: Schäfer
authors.forename: Lionel
authors.initials: L
authors.lastname: Dutruch
authors.forename: Cédric
authors.initials: C
authors.lastname: Garnier
authors.forename: Erwan
authors.initials: E
authors.lastname: Tessier
authors.forename: Duc Huy
authors.initials: DH
authors.lastname: Dang
authors.forename: Laurent
authors.initials: L
authors.lastname: Lanceleur
authors.forename: Jean-Ulrich
authors.initials: JU
authors.lastname: Mullot
authors.forename: Véronique
authors.initials: V
authors.lastname: Lenoble
authors.forename: Gérard
authors.initials: G
authors.lastname: Blanc
mesh_terms: D061006:Bays / Q000737:chemistry*; D004784:Environmental Monitoring; D005602:France; D019015:Geologic Sediments; D006207:Half-Life; D009947:Organotin Compounds / Q000032:analysis; D014001:Tin / Q000032:analysis*; D014220:Trialkyltin Compounds / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data*
chemical_list: D009947:Organotin Compounds; D014220:Trialkyltin Compounds; D014874:Water Pollutants, Chemical; C516409:mono-n-butyltin; C056189:di-n-butyltin; C011559:tributyltin; D014001:Tin