Groundwater pathways for chloride pollution of lakes
Wisconsin’s lakes are important economic, aesthetic, and recreational assets of the state. The northern Wisconsin lake district has one of most dense concentrations of lakes in the world. Like most northern states Wisconsin has been using common halite (road salt) as a deicing agent, and in much larger quantities since 1957-58. Increased chloride concentrations in the. nation’s surface waters have long been recognized.(Smith et al. , 1987). The potential effects of road salt on groundwaters have been addressed in the literature with principal concern expressed for the elevated concentrations in public drinking water, especially to people with susceptibility to hypertension and heart disease, and for the potential effects of excessive shallow groundwater chlorides on vegetation (Moses, 1980; Brandt, 1973; Zelazny and Blaser, 1970; Hanes ee al., 1976). In spite of this concern little attention has been paid to groundwater systems in terms of their relative importance as pathways to lakes and well waters. Much research has been done on road salt effects in all parts of the hydrological cycle and it is not my intent to provide a comprehensive review here. Many recent articles of interest to the reader may be found in Bubeck and Burton (1987). Some ideas presented herein are not particularly new, but in the following discussion I hope to show some additional evidence for pathways of road salt contamination, how the data can be used to determine loading rates on lake systems, and to express some newer ideas about the potential effects of road salt deicing on lake and groundwater systems. The purpose of this paper is to acquaint the reader with some of the evidence for road salt contamination in groundwater systems in Wisconsin, and to demonstrate how these pathways are significant vectors of salt and other potential contaminants to lake systems. The focus will be on two areas in Wisconsin, the first relatively pristine and the second urbanized, and the critical similarities and dissimilarities between the two.
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