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Allison Cekala

U.S. rivers are getting saltier, potentially compromising drinking water

The bomb cyclone that hit the northeastern United States last week left roadways and vehicles caked in a white film of road salt and grime. Those salts might be washing into the region’s fresh waterways, a new study reveals. A 50-year-long analysis of hundreds of U.S. Geological Survey monitoring sites finds salts in freshwater rivers and streams are rising across much of the nation. That could mean compromised drinking water akin to the crisis that struck Flint, Michigan, in 2014 when the city switched its water source to the highly salted Flint River. But road salts and deicers, mostly made of the same stuff as table salt, are not the only culprits. Researchers discovered additional salt ions—potassium, magnesium, and calcium, among others—are also increasing in the country’s freshwater rivers. Water pH increased at 66% of sites, meaning many waterways are becoming more alkaline. Those changes varied by region. For example, in midwestern agricultural areas, potassium levels rose fastest, likely from fertilizer runoff, whereas salt numbers swelled most rapidly in the densely populated and humid Northeast. Such changes were largely missing in the arid West. Taken together, the “freshwater salinization syndrome” researchers describe today in the Proceedings of the National Academy of Sciences could be an issue for people with high blood pressure that require a low-sodium diet and patients who need kidney dialysis. And salt can make water more corrosive, which tends to leach more lead from pipes, as happened in Flint. The researchers say strategies such as replacing old water pipes, updating salt-spreading equipment, and using brine instead of granulated salts on roadways could help alleviate the problem.