MODELING AND RISK ASSESSMENT OF TRIBUTYLTIN ACCUMULATION IN THE FOOD-WEB OF A SHALLOW FRESH-WATER LAKE

Tributyltin (TBT) measurements in a food web in the freshwater Lake We steinder are used to calibrate an integrated fate and bioaccumulation model with special attention given to exposure pathways. The Dutch ban on antifouling paints containing TBT is simulated with a load reducti on scenario. By integrating Monte-Carlo sampling with a calibration pr ocedure, probability distributions of TBT concentrations in the food w eb are matched to the measured variation in TBT concentrations. Subseq uently, these distributions are used for a dynamic risk analysis of TB T accumulation in water, sediment, and the food web in the whole lake and a typical marina. Model predictions indicate a fast decrease of co ncentrations in water, suspended matter, and the zebra mussel Dreissen a polymorpha. TBT concentrations in sediment, chironomids, amphipods, and benthivorous fish are predicted to decrease at a much slower rate, Simulations indicate that TBT in the sediment contributes significant ly to uptake of TBT by several species, The relative proportion of sed iment uptake increases for (partly) benthivorous fish after TBT load r eduction. The model predicts low bioaccumulation risks for the whole l ake, but substantial risks of TBT are calculated for fish and zooplank ton in marinas, both before and during load reduction.