Organotin survey in the Adour-Garonne basin.

Organotin monitoring was performed in waters of 11 rivers of the southwest of France during a 9 months period, between February and October 2001. Surface sediments were studied during the summer. Eighteen sampling points were chosen as representative of specific industrial or agricultural activities. In most samples, organotins were detected and butyltins are the most frequently present, with concentrations ranging over 0.2-30 ng(Sn)/L. Phenyltins were detected especially in spring and at the end of summer, which corresponds to likely diffusion from agricultural sources. Some high butyl- and phenyltin concentrations up to 700 ng(Sn)/L occurred during the spring where pesticides for agricultural activities were largely used. Octyltins were present in water frequently as well, with lower concentrations, probably originating from continuous leaching of plastics. Sediments appeared contaminated by the same species, with higher monobutyltin concentrations of about 30-40 microg(Sn)/kg which shows the importance of biological degradations occurring in surface sediments. This non-pesticidal organotin compounds can also be introduced from leaching of organotin-stabilized PVC by water. Using the different organotin concentrations obtained and other physico-chemical parameters measured, such as temperature or water flow rate, a statistical study was performed by principal component analysis. The results obtained allow the main sources of organotin diffusion to be identified and the hydrological cycle of these compounds better understand.