HR: 08:45h
AN: NB31D-02    [Abstracts]
TI: Transport Distance Effects in Regional Predictions of Nitrate Discharge: Implications for Nitrogen Transformation
AU: * Baker, M E
EM: bakerm@si.edu
AF: Smithsonian Environmental Research Center, 647 Contees Wharf Rd, P.O. Box 28, Edgewater, MD 21037-0028 United States
AU: Weller, D E
EM: wellerd@si.edu
AF: Smithsonian Environmental Research Center, 647 Contees Wharf Rd, P.O. Box 28, Edgewater, MD 21037-0028 United States
AU: Jordan, T E
EM: jordant@si.edu
AF: Smithsonian Environmental Research Center, 647 Contees Wharf Rd, P.O. Box 28, Edgewater, MD 21037-0028 United States
AB: Recent publications suggest that lotic uptake plays a significant role in basin-scale nitrogen transformation. If transport through terrestrial or aquatic systems has significant, generalizable impacts on nitrogen discharge at the scale of whole watersheds, then predictions of nitrogen losses should depend on both amounts of source area and transport distances from source areas to watershed outlets. We calculated terrestrial and stream transport distances from croplands along surface flow pathways to explore effects of transport and stream size on nitrate concentrations in streams draining 420 rural watersheds in 4 physiographic provinces of the Chesapeake Basin. Transport-distance distributions were statistically related to average nitrate concentrations using non-linear regression models with fitted coefficients representing transport-distance effects. Results were compared to models predicting nitrate solely from percent cropland. In three of four provinces, accounting for transport distance improved nitrate predictions and coefficients representing transport terms were statistically significant. In Coastal Plain watersheds, predictive improvements were solely attributable to terrestrial transport, whereas channel transport in larger order streams accounted for predictive improvements within the Piedmont and Appalachian Plateau. Our results provide broad-scale support for the general significance of both aquatic and terrestrial transformations, yet suggest the relative importance of these processes varies among physiographic settings.
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 1806 Chemistry of fresh water
DE: 1871 Surface water quality
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly