Fate of14C-labeled tributyltin in an estuarine microcosm

A radiotracer experiment was conducted in a controlled experimental ecosystem (microcosm) to determine the persistence and behavior of tributyltin (TBT) under conditions simulating a temperate, shallow estuarine ecosystem. Radiolabeled TBT was introduced to the estuarine microcosm, which contained estuarine water, sediment and fish. TBT and its degradation products were monitored for 40 days. TBT rapidly distributed among the compartments of the microcosm. The TBT half-life in the water column was 2.55 days for the first 11 days and then slowed to 13.4 days. More than 60% of the TBT and its metabolites were found in the sediment, indicating that the sediment was an important sink for butyltins. Higher concentrations of butyltins, relative to the water column concentrations, were found in the surface microlayer. TBT could be bioconcentrated by the fish to levels more than 200 times the exposure concentration, and underwent rapid degradation in the fish body, so that high concentrations of its metabolites were found in the fish. The concentrations of TBT adsorbed on the suspended particles were three orders of magnitude greater than that in dissolved form.