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This article in JEQ

  1. Vol. 40 No. 2, p. 634-646
    unlockOPEN ACCESS
     
    Received: July 26, 2010


    * Corresponding author(s): harris10@umbc.edu
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doi:10.2134/jeq2010.0335

Denitrification in Alluvial Wetlands in an Urban Landscape

  1. Melanie D. Harrison *a,
  2. Peter M. Groffmanb,
  3. Paul M. Mayerc,
  4. Sujay S. Kaushald and
  5. Tamara A. Newcomerd
  1. a Marine Estuarine and Environmental Science Program, Univ. of Maryland Baltimore County, 1000 Hilltop Cir., Baltimore, MD 21250, and National Oceanic and Atmospheric Administration, Southwest Region, Protected Resources Division, 777 Sonoma Ave., Santa Rosa, CA 95404
    b Cary Institute of Ecosystem Studies, Millbrook, NY 12454
    c USEPA, National Risk Management Research Lab., Ground Water and Ecosystems Restoration Division, Ada, OK 74820
    d Dep. of Geology and Earth Systems Science Interdisciplinary Center, Univ. of Maryland, College Park, MD 20740. Assigned to Associate Editor Robert Malone

Abstract

Riparian wetlands have been shown to be effective “sinks” for nitrate N (NO3 ), minimizing the downstream export of N to streams and coastal water bodies. However, the vast majority of riparian denitrification research has been in agricultural and forested watersheds, with relatively little work on riparian wetland function in urban watersheds. We investigated the variation and magnitude of denitrification in three constructed and two relict oxbow urban wetlands, and in two forested reference wetlands in the Baltimore metropolitan area. Denitrification rates in wetland sediments were measured with a 15N-enriched NO3 “push–pull” groundwater tracer method during the summer and winter of 2008. Mean denitrification rates did not differ among the wetland types and ranged from 147 ± 29 μg N kg soil−1 d−1 in constructed stormwater wetlands to 100 ± 11 μg N kg soil−1 d−1 in relict oxbows to 106 ± 32 μg N kg soil−1 d−1 in forested reference wetlands. High denitrification rates were observed in both summer and winter, suggesting that these wetlands are sinks for NO3 year round. Comparison of denitrification rates with NO3 standing stocks in the wetland water column and stream NO3 loads indicated that mass removal of NO3 in urban wetland sediments by denitrification could be substantial. Our results suggest that urban wetlands have the potential to reduce NO3 in urban landscapes and should be considered as a means to manage N in urban watersheds.

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