Evidence for the use of organic carbon as the sorbing matrix in the modeling of PCB accumulation in phytoplankton

This report presents empirical evidence for the use of organic carbon as the sorbing matrix in the kinetic modeling of PCB accumulation in phytoplankton. A kinetic-based model was used to predict congener-specific bioaccumulation factors of PCBs in phytoplankton samples collected from Green Bay, Lake Michigan. These values were compared to the measured bioaccumulation factors, and the sum of the residuals was used to evaluate the model's predictive quality. The sorbing matrix fraction (F-M) that minimized the sum of residuals of the model was then solved by iteration. The appropriateness of using dry weight, organic carbon fraction, or lipid fractions as the sorbing matrix fraction was determined by measuring their correlation to the optimum F-M. It was determined that the F-M correlated best with the organic carbon fraction, and this correlation appeared to be independent of both the spatial and seasonal differences of the field samples.