Tracking nonpoint source nitrogen pollution in human-impacted watersheds
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Abstract
Nonpoint source nitrogen (N) pollution is a leading contributor to U.S. water quality impairments. We combined watershed N mass balances and stable isotopes to investigate fate and transport of nonpoint N in forest, agricultural, and urbanized watersheds at the Baltimore Long-Term Ecological Research site. Annual N retention was 55%, 68%, and 82% for agricultural, suburban, and forest watersheds, respectively. Analysis of δ15N-NO3–, and δ18O-NO3– indicated wastewater was an important nitrate source in urbanized streams during baseflow. Negative correlations between δ15N-NO3– and δ18O-NO3– in urban watersheds indicated mixing between atmospheric deposition and wastewater, and N source contributions changed with storm magnitude (atmospheric sources contributed ∼50% at peak storm N loads). Positive correlations between δ15N-NO3– and δ18O-NO3– in watersheds suggested denitrification was removing septic system and agriculturally derived N, but N from belowground leaking sewers was less susceptible to denitrification. N transformations were also observed in a storm drain (no natural drainage network) potentially due to organic carbon inputs. Overall, nonpoint sources such as atmospheric deposition, wastewater, and fertilizer showed different susceptibility to watershed N export. There were large changes in nitrate sources as a function of runoff, and anticipating source changes in response to climate and storms will be critical for managing nonpoint N pollution.
Publication type | Article |
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Publication Subtype | Journal Article |
Title | Tracking nonpoint source nitrogen pollution in human-impacted watersheds |
Series title | Environmental Science & Technology |
DOI | 10.1021/es200779e |
Volume | 45 |
Issue | 19 |
Year Published | 2011 |
Language | English |
Publisher | American Chemical Society |
Contributing office(s) | Toxic Substances Hydrology Program |
Description | 8 p. |
First page | 8225 |
Last page | 8232 |
Online Only (Y/N) | N |
Additional Online Files (Y/N) | N |
Google Analytic Metrics | Metrics page |