Effect of primary productivity and vertical mixing on pcb dynamics in planktonic model ecosystems

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Abstract
Radiolabeled polychlorinated biphenyls (PCBs) [14C]‐Aroclor 1242 were added to large planktonic model ecosystems. Two experiments were conducted to determine the influence of turbulent mixing and primary productivity on fate and transport of PCBs. High productivity increased the proportion of added PCBs that were adsorbed to particulate matter and sedimented. Retention of added PCBs within the model ecosystems increased the recovery in a budget of added PCBs. Volatilization losses increased at the high‐mixing and low‐productivity level. Highest recovery was with a high productivity‐low mixing treatment. A third experiment was conducted in which PCBs adsorbed to clay were added to the hypolimnion of one model ecosystem. Results confirmed that PCBs unaccounted for in a budget of PCBs added to the epilimnion in the same manner were lost due to volatilization. A linear‐fate model was developed to describe 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 particulate PCBs that were probably adsorbed to colloids and fine particulates was operationally measured with the soluble fraction.