ASSESSING CHEMICAL BEHAVIOR AND DEVELOPING REMEDIAL ACTIONS USING A MASS-BALANCE MODEL OF CHEMICAL FATE IN THE BAY-OF-QUINTE

A multi-segment model of chemical fate and transport in the Bay of Qui nte and a food chain model that simulate average annual conditions, ar e used to examine the behavior of arsenic (As), pentachlorophenol (PCP ) and polychlorinated biphenyls (PCBs) in the Bay, an ''Area of Concer n'' in the Great Lakes. The Bay model was used to predict the status o f As and PCP from known loading data, but for PCBs with unknown loadin gs, the Bay and food chain models were used to ''back-calculate'' tota l loadings to the Bay. Chemical behavior depends on the characteristic s of the Bay and physical-chemical properties of chemicals. Short wate r residence times of less than a week to several months result in chem icals being advected, unless subject to other, more rapid processes. I n Upper Bay, rapid rates of sediment deposition and resuspension retar d losses by advection of persistent chemicals such as PCBs and As, des pite As being largely dissolved in the water column. Overall, behavior in Upper Bay is dominated by sediment-water exchange, and in Lower Ba y by water exchange with Lake Ontario. Because of PCP's rapid transfor mation rate in the water column, most chemical is transformed before i t reaches the sediments or downstream segments. It is recommended that elevated As inputs from the Moira River must be controlled to reduce in-Bay water and sediment concentrations, and for PCP, industrial disc harges must be reduced. If reduced, concentrations in the Bay would re spond within 3 months, I month and 3 years in the water, and about 6, 3 and 10 years in sediments for As, PCP and PCBs, respectively.