In related work, several of Stefan's graduate students, including Eric Novotny and Andrew Sander, have documented a small but steady rise in salinity in dozens of the area's lakes over the last two decades. Records show an average rise of 1.5 milligrams of salt per liter of lake water each year. "That in itself is small," Stefan said. "But if you continue the process for another 100 years, you begin to violate the standards for chronic exposure to organisms." Because salt water is heavier than freshwater, the bottoms of many lakes are already salty enough to be toxic to organisms, Stefan added. And salt levels appear to remain high throughout the year, not just during the spring melt season. The new work emphasizes the need to train road-salt applicators to use only the minimum amount of salt needed to melt ice, said Steven Corsi, a research hydrologist with the United States Geological Survey in Middleton, Wisc. Still, he said, the problem is a political hot potato that does not have an easy fix. "There's certainly a lot of evidence about the impact of road salt on the environment," Corsi said. "But it hasn't received a lot of attention because it's a tough issue to handle. It's a human safety issue versus an environmental issue. That's a tough nut to crack." Related Links: |
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