EFFECT OF OLIGOCHAETE BIOTURBATION ON SEDIMENT ACCUMULATION OF 2,2',4,4'-TETRACHLOROBIPHENYL

The influence of clay content, organic carbon, and bioturbation on sed iment accumulation of 2,2',4,4'-tetrachlorobiphenyl (TCB) was investig ated in microcosms. Four types of sediments differing in porosity, den sity, organic carbon, and clay content were used in the study. The sed iments, with or without oligochaete bioturbation, mere exposed for 100 days to water with a constant concentration of C-14-labeled TCB, in a continuous-flow system. The hypothesis for the experiment was that bi oturbation would enhance the accumulation rate of TCB by redistributin g the sediment particles and/or by changing the physical properties, e .g., porosity of the sediment, in a way that would increase the diffus ion rate. The highest accumulation was found in sediments of low organ ic carbon content. No effect of clay content was found. Contrary to th e hypothesis, bioturbation did not increase sediment accumulation of T CB. Instead, the sediment accumulation could be explained by retarded diffusion, a combined effect of the processes of adsorption and diffus ion. (C) 1997 Academic Press.