ORGANOTINS IN FRESH-WATER HARBORS AND RIVERS - TEMPORAL DISTRIBUTION, ANNUAL TRENDS AND FATE

The occurrence of butyltin and phenyltin compounds in water, mussels, and sediment of freshwater boat harbors of Lake Lucerne, Switzerland, and six Swiss river systems was determined between 1991 and 1993 following the sales ban of organotin-containing antifouling paints. In harbor waters, average levels of tributyltin (TBT) were between 40 and 50 ng/L in 1993, which was one order of magnitude lower than in 1988. Residues of up to 9.2 mu g/g TBT and 0.7 mu g/g triphenyltin (TPT) occurred in zebra mussels (Dreissena polymorpha) and were related to the water concentrations. In a sediment core, high levels of TBT and TPT occurred in the upper 7 cm and 5.5 cm, respectively, with significant decreases below. Estimated sedimentation rates and the fact that transformation products did not increase with depth indicate that TBT and TPT are persistent in these sediments. In all rivers, di- and/or monobutyltin of up to 46 ng/L occurred consistently, and occasionally TBT and TPT of up to 26 and 11 ng/L, respectively. This study indicates that even though regulations were effective in reducing TBT and TPT levels in boat harbor water, contamination of surface fresh waters including rivers by organotin compounds is still widespread and has ecotoxicological consequences. Moreover, harbor sediments represent long-term reservoirs of these compounds.