BIOACCUMULATION OF PCBS BY ALGAE - KINETICS VERSUS EQUILIBRIUM

The objectives of this study were to test the hypothesis that bioaccumulation of hydrophobic organic compounds (HOCs) by phytoplankton is correlated to the compound's octanol/water partition coefficient (K(ow)) in a predictive relationship in laboratory experiments, and to confirm these findings with field observations. In laboratory experiments we measured the uptake of 40 representative polychlorinated biphenyl (PCB) congeners over time under conditions that inhibited and allowed phytoplankton growth. Results indicated that the bioaccumulation process is consistent with partitioning from water into cell lipids but is slower than previously thought. The uptake of PCBs was slow relative to growth of phytoplankton, preventing the chemical from reaching thermodynamic equilibrium in algal cells under conditions promoting growth (nonwinter). Thus under nonwinter field conditions, many PCB congeners never reach equilibrium concentrations. Food-chain models that assume equilibrium between HOCs and the primary trophic level could be inaccurate and may need to use a kinetic framework.