Source of organotin at a marine water/sediment interface — A field study

Tributyltin (TBT) was banned in Sweden by January 1989 and the concentration of TBT was expected to decline in ambient waters. Investigations at the study site in 1989 and 1990, indicated that peak concentrations of water column TBT no longer were associated with the launching of boats in the spring, but occurred more than one month later. In the present study the possibility that TBT was released from the sediment to the water column was investigated by analysing water and sediment samples during the summer, and by in situ extraction with solvent-filled dialysis membranes. A temporal correlation between TBT concentration in water and sediment was detected, and TBT to DBT ratios in the water column were typical of TBT input. This, and a vertical stratification of TBT in the water column indicates that TBT was not transported from the sediment to the water column. During the peak of TBT in the water column no increase in extractability of TBT in the sediment was detected by in situ extraction. The source of the peak concentration of TBT has been identified as a source specifically releasing TBT and is concluded to be, e.g., paint chips in the marina area or boats not obeying the ban. The TBT concentration of waters and sediments still represents an exotoxicological risk three years after the ban on TBT antifouling paints was imposed in Sweden.