Diffuse (Non-Point) Source Loading of Chemicals to Lake Erie

Abstract

Studies of chemical loadings to Lake Erie over the last two decades show that the lake, because of its small volume to drainage area ratio, and the intensive agricultural, industrial, and urban land uses of its watersheds, has been a receptor of a myriad of natural and anthropogenic chemicals. Of these, phosphorus, trace metals, PCBs and other organics and pesticides have received the most attention. Phosphorus reduction plans already in place have produced dramatic decreases in point-source P loadings and observable improvements in lake water quality. Target P loads for complete lake restoration will not be met, however, until substantial reductions of agricultural non-point sources are obtained, and gains in this area are likely to be much slower and more difficult to attain. Source reductions of trace metals and the older chlorinated insecticides have produced some decreases in diffuse loadings of these chemicals although their biomagnification in lake biota means that their impact on the lake will continue for many years. Today, the emphasis has shifted to a broader range of anthropogenic organic chemicals including highly mobile herbicides which have been shown to contaminate Lake Erie basin drinking water supplies, and to easily biomagnified toxics which, with relatively small loadings, can have a major impact on higher species.