ORGANOTINS IN SWISS LAKES AFTER THEIR BAN - ASSESSMENT OF WATER, SEDIMENT, AND DREISSENA-POLYMORPHA CONTAMINATION OVER A 4-YEAR PERIOD

The effect of a legal ban on antifouling paints containing organotin compounds (1988, to be fully enforced within two years) was studied in Swiss freshwater ecosystems. Between 1990 and 1993, organotins were monitored in water, sediment, and zebra mussel tissue (Dreissena polymorpha) from four lakes (one marina and one natural reference site per lake). The analytical technique was a gas chromatography method using FPD detection after methylation or hexylation. In the studied marinas, no significant decrease in concentrations was detected in sediment and zebra mussel tissue; a reduction was measured in water. The levels observed are probably due to the continuing use of antifouling paints still containing organotins, and to a slow degradation in sediment. A survey conducted among boat owners of the studied marinas allowed us to estimate that an average 25% of boats were still protected by organotin-containing antifoulings one to two years after the new legislation. Zebra mussels, used as biomonitors, showed very high concentrations of tributyltin (up to 49 mu g/g dry weight). No shell thickening or other growth effect was observed. In the reference sites, much lower levels were detected.