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ROAD SALT APPLICATION CREATES A UNIQUE CHLORIDE BIOCHEMISTRY IN AN URBAN STREAM OF THE CHESAPEAKE BAY WATERSHED
Citation:
MAYER, P. M., E. A. STRIZ, E. DOHENY, S. KAUSHAL, AND P. GROFFMAN. ROAD SALT APPLICATION CREATES A UNIQUE CHLORIDE BIOCHEMISTRY IN AN URBAN STREAM OF THE CHESAPEAKE BAY WATERSHED. Presented at American Geophysical Union Meeting, Baltimore, MD, May 22 - 26, 2006.
Impact/Purpose:
To inform the public.
Description:
Recent evidence from the mid-Atlantic suggests that freshwater supplies are threatened by chronic chloride inputs from road salts applied to improve highway safety. Elevated chloride levels also may limit the ability of aquatic systems to microbially process nitrate nitrogen, a nutrient whose elevated levels pose human and ecological threats. Understanding the behavior of chloride in urban watersheds where road salts are applied is critical to predicting subsequent impacts to ecosystem health and drinking water supplies. Here we report on a long-term study of water chemistry in Minebank Run, a recently restored stream in an urban watershed of Towson, MD that receives chronic chloride inputs from the 695 Beltway highway and connecting arteries. Chloride, sodium, and specific conductance were greatly elevated in the both surface water and ground water of Minebank Run, spiking in correspondence to road salt application in the winter. Chloride levels were consistently higher in ground water of the bank side of a minor roadway and downstream of the 695 Beltway. Surface water chloride levels remained elevated throughout the year apparently because ground water continued to supply surface water with chloride even after road salt application ceased. Thus, ground water may represent a chronic source of chloride to surface water, thereby contributing to the upward trend in freshwater salinity in urbanizing areas. Stream susceptibility to road salt impacts may depend upon ground water hydrology and stream geomorphology. However, geomorphic stream restoration practices widely used in the mid-Atlantic are not designed to address salinity effects. Source control of road salts may be necessary to reduce environmental risk.