Sorption kinetics and transformation of DDT in sediment

The overall objective of this study was to investigate the sorption kinetic s of DDT in sediment under similar experimental conditions employed in corr esponding toxicity studies for bentic organisms. A batch of aerated Schoonr ewoerdse Wiel sediment, initially spiked with DDT, was sampled over a perio d of seven days. Concentrations of DDT, DDD and DDE were determined in both the solid and the solution phase in the sediment/water system after separa tion by centrifugation. It was found that the extractable amount of DDT dec reased with increasing contact time. This can partly be explained in terms of transformation of DDT into DDD. Furthermore, the present applied extract ion procedure seems to be less effective with increasing contact time, indi cating an increase in binding strength of DDT with the sediment material. F inally, on the basis of DDT, DDE and DDD concentrations in both the solid p hase and the solution phase, partition coefficients were calculated, which appeared to be independent of the contact time. This points at a very rapid equilibrating between DDT in pore water and in the extractable forms adsor bed at the solid phase.