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Sources and transport of nitrogen in arid urban watersheds

Hale, Rebecca; Turnbull, Laura; Earl, Stevan; Grimm, Nancy; Riha, Krystin; Michalski, Greg; Lohse, Kathleen; Childers, Dan

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Rebecca Hale

Laura Turnbull

Stevan Earl

Nancy Grimm

Krystin Riha

Greg Michalski

Kathleen Lohse

Dan Childers



Urban watersheds are often sources of nitrogen (N) to downstream systems, contributing to poor water quality. However, it is unknown which components (e.g., land cover and stormwater infrastructure type) of urban watersheds contribute to N export and which may be sites of retention. In this study we investigated which watershed characteristics control N sourcing, biogeochemical processing of nitrate (NO3–) during storms, and the amount of rainfall N that is retained within urban watersheds. We used triple isotopes of NO3– (δ15N, δ18O, and Δ17O) to identify sources and transformations of NO3– during storms from 10 nested arid urban watersheds that varied in stormwater infrastructure type and drainage area. Stormwater infrastructure and land cover—retention basins, pipes, and grass cover—dictated the sourcing of NO3– in runoff. Urban watersheds were strong sinks or sources of N to stormwater depending on runoff, which in turn was inversely related to retention basin density and positively related to imperviousness and precipitation. Our results suggest that watershed characteristics control the sources and transport of inorganic N in urban stormwater but that retention of inorganic N at the time scale of individual runoff events is controlled by hydrologic, rather than biogeochemical, mechanisms.


Hale, R., Turnbull, L., Earl, S., Grimm, N., Riha, K., Michalski, G., …Childers, D. (2014). Sources and transport of nitrogen in arid urban watersheds. Environmental Science and Technology, 48(11), 6211-6219.

Journal Article Type Article
Publication Date Jun 3, 2014
Deposit Date May 7, 2014
Publicly Available Date Oct 27, 2014
Journal Environmental Science and Technology
Print ISSN 0013-936X
Electronic ISSN 1520-5851
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 48
Issue 11
Pages 6211-6219


Accepted Journal Article (1.2 Mb)

Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science and Technology, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see

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