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The Fate of Groundwater Ammonium in a Lake Edge Wetland
Author(s) -
Lusby Fleur E.,
Gibbs Max M.,
Cooper A. Bryce,
Thompson Keith
Publication year - 1998
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1998.00472425002700020029x
Subject(s) - nitrification , typha , ammonium , environmental chemistry , denitrification , groundwater , wetland , willow , sediment , environmental science , surface water , nitrogen , hyporheic zone , nitrate , mineralization (soil science) , chemistry , hydrology (agriculture) , environmental engineering , soil water , ecology , soil science , geology , biology , paleontology , geotechnical engineering , organic chemistry
The removal of ammonium—nitrogen (NH 4 ‐N) from groundwater flowing through a grey willow ( Salix cinerea ) and native raupo ( Typha orientalis ) lake edge wetland was investigated over 10 mo. Monthly groundwater sampling showed that more than 95% of incoming NH 2 ‐N was removed by the wetland. Laboratory assays found that the potential for NH 4 ‐N removal by nitrification and subsequent denitrification was significantly higher in the organic surface sediments than in deeper, sandy, root zone sediments. In a laboratory 15 N‐tracer experiment, Salix cinerea and Typha orientalis readily assimilated NH 2 ‐N from the root zone and were found to enhance the natural diffusion of NH 4 ‐N up through the organic sediment layer and into the overlying water. Estimated rates of removal of NH 2 ‐N by coupled nitrification‐denitrification and plant assimilation were 8 to 9 mg of N m −2 d −1 and 9 to 46 mg of N m −2 d −1 , respectively. Assimilated N, returned to the overlying water‐sediment surface via litter fall may be subject to sequential mineralization, nitrification, and denitrification, resulting in gaseous N loss. Sixty‐five percent of the 15 N in Salix leaf litter was transformed in such a way. The results of this study indicate that plants play a central role in the NH 4 ‐N processing capacity of wetlands. The relevance of our findings to constructed wetland design is discussed.