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THE EFFECTS OF ECOSYSTEM RESTORATION ON NITROGEN PROCESSING IN AN URBAN MID-ATLANTIC PIEDMONT STREAM
Citation:
Mayer*, P. M., E Striz*, R. Shedlock, E. Doheny, AND P. M. Groffman. THE EFFECTS OF ECOSYSTEM RESTORATION ON NITROGEN PROCESSING IN AN URBAN MID-ATLANTIC PIEDMONT STREAM. Presented at Urban Ecology Session-Ecological Society of America, Tucson, AZ, 08/4-9/2002.
Description:
Elevated nitrate levels in streams and groundwater pose human and ecological threats. The US Environmental Protection Agency, US Geological Survey, Institute of Ecosystem Studies, and Baltimore County Dept. of Environmental Protection and Resource Management are collaborating on a multi-year study of the impacts of stream restoration on nitrogen processing in Minebank Run, a piedmont stream in Baltimore County, Maryland. The study is designed to investigate the nitrate removal capacity of this stream reach before and after restoration. Restoration techniques such as bank re-shaping, bank reinforcement, and energy dissipation structures will be implemented to reestablish geomorphic stability lost due to impacts from storm water runoff. We will quantify the effects of specific restoration techniques on microbial denitrification, a process that removes nitrate but which requires anaerobic (saturated) conditions and adequate supply of dissolved organic carbon. Restoration may enhance denitrification by increasing groundwater table to levels in contact with carbon rich soils or by increasing supply of organic material (carbon) to denitrifers in the subsurface. Subsurface lithology in the watershed is being characterized from deep soil cores and from seismic refraction analysis of bedrock layers. Stream geomorphology, surface flow, and geochemistry are being be quantified throughout the stream reach. Tracer tests will be conducted to identify hyporheic flow paths. Groundwater hydrology and geochemical monitoring is underway in a network of 51 wells and piezometers installed in the stream channel corresponding to the restoration techniques of interest. 3-D hydrologic models of nitrate movement will be developed for the watershed. Denitrification potential and actual in situ denitrification rates will be measured throughout the well network and related to carbon residence and availability for denitrifiers as well as persistence of anoxic conditions in the subsurface. Our study results will be used to develop stream restoration approaches for reducing nitrate pollution in watersheds.