Quantitative information about the fate of applied nitrate (NO3-N) in pulse-flow constructed wetlands is essential for designing wetland treatment systems and assessing their nitrogen removal services for agricultural and stormwater applications. Although many studies have documented NO3-N losses in wetlands, controlled experiments indicating the relative importance of different processes and N sinks are scarce. In the current study, 15NO3-N isotope enrichment tracer experiments were conducted in wetland mesocosms of two different wetland soil types at two realistic agricultural NO3-N source loads. The 15N label was traced from the source NO3-N into plant biomass, soil (including organic matter and ammonium), and N-gas constituents over 7–10 day study periods. All sinks responded positively to higher NO3-N loading. Plant uptake exceeded denitrification 2–3 fold in the low NO3-N loading experiments, while both fates were nearly equivalent in the high loading experiments. One to two years later, soils largely retained the assimilated tracer N, whereas plants had lost much of it. Results demonstrated that plant and microbial assimilation in the soil (temporary N sinks) can exceed denitrification (permanent N loss) in pulse-flow environments and must be considered by wetland designers and managers for optimizing nitrogen removal potential.
|Number of pages||12|
|State||Published - Sep 2017|
Bibliographical noteFunding Information:
The wetland mesocosm project was supported in part with funds provided by the North Carolina Sea Grant and the Water Resources Research Institute of the University of North Carolina Research Grant. Additional funding for the research described in this article was provided by the United States Environmental Protection Agency (EPA) under the Science to Achieve Results (STAR) Graduate Fellowship Program, by the National Science Foundation (NSF) EAR 1024662, and by the USGS Water Mission Area National Research Program. Isotopic analyses of nitrate and nitrogen gas were performed by Janet Hannon and Stan Mroczkowski at USGS. Helpful comments on the manuscript were provided by Greg Noe, Alex Horne, and an anonymous reviewer. EPA has not officially endorsed this publication and the views expressed herein may not reflect the views of the EPA. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
© 2017 Elsevier B.V.
- N tracer
- Nitrate cycling
- Plant uptake
- Pulse-flow treatment wetland
- Wetland restoration
ASJC Scopus subject areas
- Environmental Engineering
- Nature and Landscape Conservation
- Management, Monitoring, Policy and Law