THE INFLUENCE OF NA2S ON THE METHYLATION OF TRIMETHYLTIN AND TRIMETHYLLEAD IN ENVIRONMENTAL SEDIMENTS

Methylation experiments have been carried out with sediment samples from Aries river and Thermaikos gulf in Northern Greece. Total sulphide concentrations of 0.77-0.83 mg g(-1) and 0.1-0.15 mg g(-1) for Thermaikos gulf and Aries river respectively were found in sediment samples from these ecosystems. Methylation yield was lowered with the increase of the sulphide content in both cases. The contribution of the chemical redistribution reaction in the overall methylation process is different for the two metals, being in the range of 40-50% for trimethyltin and of 5-11% for trimethyllead. The inhibitory effect of Na2S on methylation is interpreted in terms of pH alteration of the system due to Na2S hydrolysis.