As Chicagoans basked in last week’s relative warmth, they might have spared a thought for frogs. Above-freezing temperatures melt the city’s roadside snowbanks, sending an annual average of 270,000 tons of road salt into the state’s waterways and giving flora and fauna a super-sized serving of NaCl.
Walt Kelly, a geochemist with the Illinois State Water Survey at the University of Illinois at Urbana-Champaign, said chloride levels in waterways shot up during thaws and dropped again in the summer. Sodium levels are much harder to trace.
Mr. Kelly said chloride levels have risen more than threefold over the past 50 years, creating an increasingly toxic environment for frogs, fish and aquatic plants.