Tracking Nonpoint Source Nitrogen Pollution in Human-Impacted Watersheds

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• 作者：Sujay S. Kaushal ; Peter M. Groffman ; Lawrence E. Band ; Emily M. Elliott ; Catherine A. Shields ; Carol Kendall
• 刊名：Environmental Science & Technology
• 出版年：2011
• 出版时间：October 1, 2011
• 年：2011
• 卷：45
• 期：19
• 页码：8225-8232
• 全文大小：950K
• 年卷期：v.45,no.19(October 1, 2011)
• ISSN：1520-5851

文摘

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 未¹⁵N-NO₃^{鈥?/sup>, and 未18O-NO₃鈥?/sup> indicated wastewater was an important nitrate source in urbanized streams during baseflow. Negative correlations between 未15N-NO₃鈥?/sup> and 未18O-NO₃鈥?/sup> 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 未15N-NO₃鈥?/sup> and 未18O-NO₃鈥?/sup> 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.}