Space and Earth Sciences News

This USGS report is published in the journal Environmental Science and Technology and is available as a free download online.The use of salt to deice pavement can leave urban streams toxic to aquatic life, according to a new U.S. Geological Survey study on the influence of winter runoff in northern U.S. cities, with a special focus on eastern Wisconsin and Milwaukee.More than half of the Milwaukee streams included in this study had samples that were toxic during winter deicing. In eastern and southern Wisconsin, all streams studied had potentially toxic chloride concentrations during winter, with lingering effects into the summer at some streams. Nationally, samples from fifty-five percent of streams studied in 13 northern cities were potentially toxic; twenty-five percent of the streams had samples that exceeded acute water quality criteria.  Toxicity was measured by direct testing of organisms in samples during the local study component; in the regional and the national study components, observed chloride l