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This article in JEQ

  1. Vol. 32 No. 4, p. 1534-1547
     
    Published: July, 2003


    * Corresponding author(s): jordanth@si.edu
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doi:10.2134/jeq2003.1534

Nutrient and Sediment Removal by a Restored Wetland Receiving Agricultural Runoff

  1. Thomas E. Jordan *a,
  2. Dennis F. Whighama,
  3. Kirsten H. Hofmockelb and
  4. Mary A. Pittekc
  1. a Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, MD 21037
    b Duke Univ. Dep. of Biology, Durham, NC 27708
    c Univ. of Maryland, Dep. of Biological Resources Engineering, College Park, MD 20742

Abstract

Few studies have measured removal of pollutants by restored wetlands that receive highly variable inflows. We used automated flow-proportional sampling to monitor the removal of nutrients and suspended solids by a 1.3-ha restored wetland receiving unregulated inflows from a 14-ha agricultural watershed in Maryland, USA. Water entered the wetland mainly in brief pulses of runoff, which sometimes exceeded the 2500-m3 water holding capacity of the wetland. Half of the total water inflow occurred in only 24 days scattered throughout the two-year study. Measured annual water gains were within 5% of balancing water losses. Annual removal of nutrients differed greatly between the two years of the study. The most removal occurred in the first year, which included a three-month period of decreasing water level in the wetland. In that year, the wetland removed 59% of the total P, 38% of the total N, and 41% of the total organic C it received. However, in the second year, which lacked a drying period, there was no significant (p > 0.05) net removal of total N or P, although 30% of the total organic C input was removed. For the entire two-year period, the wetland removed 25% of the ammonium, 52% of the nitrate, and 34% of the organic C it received, but there was no significant net removal of total suspended solids (TSS) or other forms of N and P. Although the variability of inflow may have decreased the capacity of the wetland to remove materials, the wetland still reduced nonpoint-source pollution.

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Copyright © 2003. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.32:1534–1547.