MOBILITY OF 2,2',5,5'-TETRACHLOROBIPHENYL IN MODEL SYSTEMS CONTAININGBOTTOM SEDIMENTS AND WATER FROM THE LOWER FOX RIVER, WISCONSIN

Sediment-water partitioning and diffusive transport of 2,2'5,5'-tetrac hlorobiphenyl, PCB congener IUPAC #52 (TCB52) were examined in laborat ory experiments with sediments from two sites in the lower Fox River, Wisconsin. Native water was pumped at controlled flow rates through ce lls containing sediments amended with a known activity of carbon-14-la beled TCB52. Concentrations of TCB52 in water and sediments were deter mined by liquid scintillation measurements of carbon-14 activity. Sedi ment-wafer partitioning was independent of flow rate for rates up to 8 m/d. Distribution coefficients (K-d) and soil-sorption coefficients ( K-oc) were found to be at maximum levels 5-10 cm below the surface, de spite an absence of significant variation in the fraction of organic c arbon (f(oc)) through the same profile. Other factors, such as the eff ects of colloids and microbial activity in the sediments, are likely t o be important in controlling the PCB distribution. Log K-d and log K- oc ranges were 4.1-4.9 and 5.3-6.1, respectively, and calculated effec tive diffusivities at the sediment-water interface ranged from 3 to 8 x 10(-10) cm(2)/s. Gradual increases with time in TCB52 concentrations in the water phase, possibly due to effects of microbial activity, we re observed. Diffusion experiments and models showed that the TCB52 mi gration rate within, the sediment column is 8-9 mm/yr.