EFFECT OF PRIMARY PRODUCTIVITY AND VERTICAL MIXING ON PCB DYNAMICS INPLANKTONIC MODEL-ECOSYSTEMS

Radiolabeled polychlorinated biphenyls (PCBs) [C-14] -Aroclor 1242 wer e added to large planktonic model ecosystems. Two experiments were con ducted to determine the influence of turbulent mixing and primary prod uctivity on fate and transport of PCBs. High productivity increased th e proportion of added PCBs that were adsorbed to particulate matter an d sedimented. Retention of added PCBs within the model ecosystems incr eased the recovery in a budget of added PCBs. Volatilization losses in creased at the high-mixing and low-productivity level. Highest recover y was with a high productivity-low mixing treatment. A third experimen t was conducted in which PCBs adsorbed to clay were added to the hypol imnion of one model ecosystem. Results confirmed that PCBs unaccounted for in a budget of PCBs added to the epilimnion in the same manner we re lost due to volatilization. A linear-fate model was developed to de scribe trends in PCB concentrations as well as fate of the added PCBs. Model parameters and predicted fate of added PCBs agreed closely with observed results. The model indicated that an unmeasured pool of part iculate PCBs that were probably adsorbed to colloids and fine particul ates was operationally measured with the soluble fraction.