CHLORIDE MODEL FOR POLLUTED ONONDAGA LAKE

The validation of a mass balance chloride (Cl) model for enriched Onondaga Lake is documented for the period 1973-1991. The history of loading of Cl to the lake, extending from the mining of NaCl brines adjoining the lake in the late 1700s, through the 102 year period of operation and discharges of an adjoining soda ash/chlor-alkali facility, is reviewed. Loads are estimated for the 1973-1991 interval based on a program of continuous flow measurements and bi-weekly monitoring of Cl concentration for the major inflows. The model performs well in matching the substantial seasonal variations in lake Cl concentration and the major reduction in concentration observed since closure of the facility in 1986 (from about 1585 to 430 mg 1(-1)). Projections with the validated model demonstrate the C1 concentration in the lake would be about 230mgl(-1), nearly 50% lower than the present concentration, without the continuing waste input from the soda ash/chlor-alkali facility.