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Journal of Environmental Quality Abstract - Ground Water Quality

Upflow Reactors for Riparian Zone Denitrification


This article in JEQ

  1. Vol. 35 No. 2, p. 412-420
    Received: Jan 24, 2005

    * Corresponding author(s): wroberts@uwaterloo.ca
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  1. Peter W. van Driel,
  2. William D. Robertson * and
  3. L. Craig Merkley
  1. D epartment of Earth Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON, Canada
    U pper Thames River Conservation Authority, 1424 Clarke Road, London, ON, Canada


We used permeable reactive subsurface barriers consisting of a C source (wood particles), with very high hydraulic conductivities (∼0.1–1 cm s−1), to provide high rates of riparian zone NO3–N removal at two field sites in an agricultural area of southwestern Ontario. At one site, a 0.73-m3 reactor containing fine wood particles was monitored for a 20-mo period and achieved a 33% reduction in mean influent NO3–N concentration of 11.5 mg L−1 and a mean removal rate of 4.5 mg L−1 d−1 (0.7 g m−2 d−1). At the second site, four smaller reactors (0.21 m3 each), two containing fine wood particles and two containing coarse wood particles, were monitored for a 4-mo period and were successful in attenuating mean influent NO3–N concentrations of 23.7 to 35.1 mg L−1 by 41 to 63%. Mean reaction rates for the two coarse-particle reactors (3.2 and 7.8 mg L−1 d−1, or 1.5 and 3.4 g m−2 d−1) were not significantly different (p > 0.2) than the rates observed in the two fine-particle reactors (5.0 and 9.9 mg L−1 d−1, or 1.8–3.5 g m−2 d−1). A two-dimensional ground water flow model is used to illustrate how permeable reactive barriers such as these can be used to redirect ground water flow within riparian zones, potentially augmenting NO3 removal in this environment.

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