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Groundwater and surface water dynamics of Na and Cl in an urban stream: effects of road salts
Cooper, C., P. Mayer, AND Bart Faulkner. Groundwater and surface water dynamics of Na and Cl in an urban stream: effects of road salts. BIOGEOCHEMISTRY. Springer, New York, NY, , 149-166, (2014).
Ecosystem restoration and safe and sustainable water resources.
AbstractRoad salts are a growing environmental and health concern in urban watersheds. We examined groundwater (GW) and surface water (SW) dynamics of Na and Cl in an urban stream, Minebank Run (MBR), MD. We observed an increasing salinity trend in this restored stream. Current baseflow salinity does not exceed water quality standards, but rapid “first flush” storm flow was approximately one-third of seawater. Comparisons between the upstream and downstream study reaches suggest that the I-695 Baltimore Beltway is the primary road salt source. Cromwell Bridge Road parallels most of MBR and was an additional source to GW concentrations, especially the downstream right bank. A baseflow synoptic survey identified zones of increased salinity. Downstream piezometer wells exhibited increases in salt concentrations and there was evidence that Na is exchanging Ca and Mg on soils. SW salt concentrations were generally elevated above GW concentrations. Salinity levels persisted at MBR throughout the year and were above background levels at Bynum Run, a nearby reference stream not bisected by a major highway, suggesting that GW is a long-term reservoir for accumulating road salts. Chronic salinity levels may be high enough to damage vegetation and salinity peaks could impact other biota. Increasing salinity may reduce the benefits of stream restoration in this urbanized stream, impact drinking water, and mobilize other chemicals of concern (e.g. N) in MBR and receiving waters of the Chesapeake Bay.