Volatilization of organotin compounds from estuarine and coastal environments

The occurrence and speciation of volatile tin compounds (Sn) have been inve stigated in a contaminated area of the Arcachon Bay (SW France)and in the w ater column of the Scheldt (Belgium/Netherlands) and Gironde (SW France) es tuaries. This paper describes the application of a multi-isotope analytical method, using gas chromatography and inductively coupled plasma-mass spect rometry. Analytes were collected by cryogenic trapping of the gaseous speci es. This trapping has allowed us to probe volatile tin compounds by detecti ng both Sn-118 and Sn-120 isotopes. Volatile organic tin compounds have bee n determined in both sediment and water. They could result from both natura l methylation and hydridization processes of inorganic tin (RnR4-n'Sn; R = Me, R' = H, n = 0-4) and from anthropogenic butyltin derivatives released f rom ship antifouling paintings which have accumulated in sediments (RnR4-n' Sn; R = Bu, R' = H or Me, n = 0-3). The most ubiquitous species were found to be the methylated forms of butyltin derivatives (BunSnMe4-n, n = 0-3). T hese results suggest that biological and/or chemical methylation mechanisms are likely to occur in sediments and to lead to remobilization of tin spec ies into the water column and subsequently to the atmosphere. Finally, sedi ment-water and water-atmosphere fluxes have been calculated to assess the p otential impact of these processes on the fate of organotin compounds in co astal environments.