By Sid Perkins
Chlorides from road salt used in the winter to clear icy highways in the northeastern United States are increasingly tainting streams throughout the region, according to long-term studies of water quality.
Measurements in rural New Hampshire, New York’s Hudson River Valley, and Baltimore County, Md., show that the concentration of chlorides in streams has risen dramatically. In the past 25 years, chloride concentrations have tripled to reach 30 milligrams per liter at some sites near Baltimore, says Peter M. Groffman of the Institute of Ecosystem Studies in Millbrook, N.Y. Over the same period, concentrations have nearly quadrupled to 70 mg/l in streams near an interstate highway in New Hampshire.