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News Release

For immediate use

Sept. 6, 2005 -- No. 393

Study: salting highways turning
Northeastís waters less drinkable

By DAVID WILLIAMSON
UNC News Services

CHAPEL HILL Ė Staggering hurricane-related problems in southern Louisiana and Mississippi are getting much of the news coverage these days, but the northeastern United States faces a major but far more subtle ecological threat of its own, a new study shows.

Spreading salt on roadways to speed up melting of snow and ice has contaminated fresh water in Northeastern rivers, streams, lakes and wells to an alarming degree, the study concludes. Detrimental effects of the practice are growing worse.

"Chloride concentrations are increasing at a rate that threatens the availability of freshwater in the Northeast," said Dr. Lawrence E. Band, chair and Voit Gilmore distinguished professor of geography at the University of North Carolina at Chapel Hill and one of the study authors. "We found chloride concentrations were frequently up to 25 percent of the concentration of seawater in streams in Maryland, New York and New Hampshire during winter. During summers, chloride concentrations remained up to 100 times greater than unaffected forest streams we used as controls."

The amount of salt in streams and other fresh waterways increased as a function of impervious surfaces such as roads and paved driveways and often well exceeded tolerances for freshwater life in suburban and urban watersheds, said Band,  of UNCís College of Arts and Sciences.

"Our analysis showed that if salinity were to increase at its present rate due to increases in impervious surfaces and current snow removal practices, as well as the use of water softeners, many surface waters in the Northeast may no longer be drinkable and would become toxic to freshwater life in less than a century."

A report on the findings appears online Monday in the Proceedings of the National Academy of Sciences. Besides Band, authors are Dr. Sujay S. Kaushal of the University of Marylandís Center for Environmental Science in Frostburg, Md.; Dr. Peter M. Groffman, Dr. Gene E. Likens and Victoria R. Kelly of the Institute of Ecosystem Studies in Millbrook, N.Y.; Kenneth T. Belt of the USDA Forest Serviceís Northeastern Research Station in Baltimore County, Md.; William P. Stack of the Baltimore Department of Public Works and Gary T. Fisher of the U.S. Geological Survey in Baltimore.

The study involved monitoring rates of salinization by measuring increases in chloride and other chemical concentrations using long-term data from streams and rivers in Baltimore County, Md., the Hudson River Valley in New York and the White Mountains of New Hampshire.

"Despite fluctuations in precipitation, we observed strong increases in the baseline concentration of chloride in rural watersheds with low density of roadways in Maryland, New York and New Hampshire," Band said. "Streams entering the Baltimore drinking water reservoir and streams and river of the Hudson River Valley also showed significant increases in chloride over the past few decades.

"This work indicates we need to re-evaluate our habits and activities to find better ways to remove snow and to limit the amount of salt we are spreading on the roads and also find other ways of treating hard water than with water softeners," he said. "We have shown that the practices we now use are leaving too much salt in ecosystems long after its application. That will damage freshwater vegetation and other life forms, including the microbial population, and may have implications for the type of disease organisms that can survive in these streams."

The new and disturbing findings show the value of long-term, continual monitoring of salinzation and comparable health and ecology issues to uncover harmful trends, Band said.

"This is becoming a chronic problem," Band said. "As we increasingly suburbanize and move further out from the cities into low density, sprawling suburbs with ground water systems, salt spread to melt snow will have increasing implications not only for aquatic life, but also for potable drinking and other human concerns."

Support for the research came in various ways from the U.S. Department of Agriculture Forest Service Northeastern Research Station, the Baltimore County Department of Environmental Protection and Management, the U.S. Geological Survey, the City of Baltimore Departments of Parks and Recreation and Public Works, the Maryland Department of Natural Resources, the National Science Foundation, the Environmental Protection Agency and the A.W. Mellon Foundation.

Baltimore is one of two urban settings that constitute part of a 25-site integrated long-term ecosystems study supported by the National Science Foundation. The Baltimore ecosystem study started in 1998 and will continue for at least another 20 years.

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Note: Band can be reached at (919) 962-3921 or lband@email.unc.edu.

News Services contact: David Williamson, (919) 962-8596