EFFECTS OF PH AND HUMUS ON THE AVAILABILITY OF 2,2',4',4',5,5'-HEXACHLOROBIPHENYL-C-14 IN LAKE WATER

The effects of treatments of lake water with lime and acid on the availability of 2,2',4,4',5,5'-hexachlorobiphenyl to aquatic organisms were studied. A closed laboratory system with hexane-filled dialysis bags of two pore sizes was used, in combination with a C-14-labeled PCB isomer and liquid scintillation counting. Although the dialysis concentration factor remained relatively low throughout the experiment, a significant relationship was found between the bioavailability of polychlorinated biphenyl (PCB) and the dissolved organic carbon (DOC) content of the lake water. The availability of PCB was raised by acid and lime treatment for lake water with low DOC content, whereas both treatments lowered the availability of PCB in water from lakes with high DOC content, compared to untreated water. The liming of the lake water did result in a significantly higher bioavailability of hexachlorobiphenyl in five of the 10 tested lakes. The acidification of the lake water had a significant effect on the bioavailability of PCB in some, but not all, of the lakes. The uptake of PCB in the hexane was inversely related to the DOC concentration of the water phase. The pH does influence the bioavailability of PCB in aquatic systems with various concentrations of humus.