Simplified model for polychlorinated biphenyls (PCBS) in GreGreen Bay

Abstract

A user -friendly microcomputer model, STOXGB (Simplified Toxic Substance Model for Green Bay) was developed and then applied to simulate the time varying fate of polychlorinated biphenyls (PCBs) in Green Bay, Lake Michigan, over the period 1940-1989. The STOXGB model, based on the Thomann and Mueller (1987) suspended and toxic substance models, includes loadings and partitioning of the contaminants between the phases of air, water, suspended and bottom sediments. Expressions for horizontal and vertical transport rates for diffusion between water and sediments, dry atmospheric deposition, volatilization, sediment deposition, burial and resuspension, and water and suspended matter inflow and outflow are also included in the model. Initial model inputs were developed by averaging calibrated parameter values from the more complex GBTOX model (Bierman et al., 1992). Despite uncertainties in the loadings of POC (particulate organic carbon) and PCBs and the simplified dynamics of the model, the results show appreciable comparability to available field data for 1989. The model was also used to explore four different managerial scenarios, corresponding to different future loading assumptions for POC and PCBs. The model predicts that, under 50% and 100% PCB loading reductions, dramatic improvements will occur in Green Bay within the next 50 years. The predicted response is most rapid for water column and inner bay segments. Further studies and recommended to identify historical loading trends of POC and PCVs to Green Bay for the period of 1940 to the present.