Effect of oligochaete bioturbation on sediment accumulation of 2,2',4,4'-tetrachlorobiphenyl.

The influence of clay content, organic carbon, and bioturbation on sediment accumulation of 2,2',4,4'-tetrachlorobiphenyl (TCB) was investigated in microcosms. Four types of sediments differing in porosity, density, organic carbon, and clay content were used in the study. The sediments, with or without oligochaete bioturbation, were exposed for 100 days to water with a constant concentration of 14C-labeled TCB, in a continuous-flow system. The hypothesis for the experiment was that bioturbation would enhance the accumulation rate of TCB by redistributing the sediment particles and/or by changing the physical properties, e.g., porosity of the sediment, in a way that would increase the diffusion rate. The highest accumulation was found in sediments of low organic carbon content. No effect of clay content was found. Contrary to the hypothesis, bioturbation did not increase sediment accumulation of TCB. Instead, the sediment accumulation could be explained by retarded diffusion, a combined effect of the processes of adsorption and diffusion.