Watershed

Oral

394997 - Characterizing Denitrification Variability within an Agricultural Constructed Wetland

Tuesday, June 5
2:00 PM - 3:30 PM
Location: Greenway IJ
Co-Authors: Lizbeth Aguirre-Jaimes, Santa Cruz, CA – University of California - Santa Cruz; Olivia Cacciatore, Villanova, PA – Villanova University

Flow through wetlands are one of the most promising available conservation interventions to reduce nitrate export from agricultural river networks. However, reported wetland nitrate removal on an event time scale is highly variable, limiting the confidence needed for widespread implementation. In this study, we assessed how denitrification and the conditions which regulate it vary with location and substrate throughout a constructed wetland located in an intensively managed row-crop agricultural landscape. We found that denitrification rate ranged over two orders of magnitude within the wetland and that the highest rate occurred when overlaying water nitrate and dissolved organic carbon concentrations were high and approximately balanced. We found denitrification was occurring on all substrates throughout the wetland including sediment, detritus and live plant tissue. Dissolved oxygen measurements showed that anoxic conditions, which favor denitrification, extended over half the water column depth for over 12 hours every day implying that substrates other that sediment may meaningfully contribute towards the microbial assemblage and overall denitrification potential of the wetland. We used these results to calculated whole wetland nitrate removal via denitrification and compared that to calculated total nitrate removal from a mass balance between the inlet and outlet. The results of this study elucidate the relative contribution of denitrification to nitrate removal in a treatment wetland, the spatial variation in rate, and the key variables regulating its efficiency. Together, this information can be used to improve treatment wetland design by identifying and promoting conditions most favorable to denitrification.

Amy Hansen

Research Associate
St. Anthony Falls Laboratory, University of Minnes

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394997 - Characterizing Denitrification Variability within an Agricultural Constructed Wetland



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