BIOACCUMULATION AND BIOAVAILABILITY OF TRIBUTYLTIN CHLORIDE - INFLUENCE OF PH AND HUMIC ACIDS

The influence of pH and humic acids on bioaccumulation and bioavailabi lity of tributyltin chloride (TBT) was studied in Daphnia and yolk sac larvae of fish Thymallus thymallus. In both organisms, bioaccumulatio n followed a first-order uptake process, and metabolism of TBT was slo w. Bioconcentration factors in Daphnia and Thymallus were 198 and 2015 , respectively. Uptake rates and bioaccumulation of TBT in Daphnia wer e significantly higher at pH 8.0, where TBT predominates as neutral TB TOH species than at pH 6.0, where it predominates as cation. Humic aci ds led to a decrease in TBT bioaccumulation at greater than or equal t o 1.8 mg . l(-1) dissolved organic carbon (DOG) in Daphnia and greater than or equal to 4.0 mg . l(-1) DOC in Thymallus larvae. Bioaccumulat ion of TBT decreased with increasing concentrations of humic acids. He nce, chemical speciation of TBT is a determinant factor for the bioava ilability, and thus bioconcentration and toxicity of this organotin co mpound.