Denitrification, N2O emissions, and nutrient export in Maryland coastal plain streams
Gardner, John Robert
Fisher, Thomas R
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Small streams are hotspots for denitrification, emissions of a potent greenhouse gas nitrous oxide (N<sub>2</sub>O), and are also highly connected to their watersheds via groundwater flowpaths. In-stream, reach scale denitrification and N<sub>2</sub>O production as well as biogenic nitrogen gases delivered by groundwater were investigated in one small agriculturally impacted watershed. Groundwater was an important source of biogenic N<sub>2</sub>, but most N<sub>2</sub>O was produced in-stream and emissions were relatively high. In addition, agricultural streams significantly contribute to nutrient loading and degradation of downstream aquatic ecosystems. Export and transport mechanisms of nitrogen and phosphorus were investigated during base and stormflow in three watersheds with varying amounts of agricultural and forested land use. Quickflow, which is associated with storms, transported most of the phosphorus and ammonium in the agricultural watersheds, but quickflow had little impact on nutrient concentrations and export in the forested watershed.