ARS | Publication request: On-site denitrification beds could reduce indirect greenhouse gas emissions from agricultural drainage waters

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 5, 2011
Publication Date: December 5, 2011
Citation: Fujinuma, R., Venterea, R.T., Ranaivoson, A., Moncrief, J., Dittrich, M. 2011. On-site denitrification beds could reduce indirect greenhouse gas emissions from agricultural drainage waters [abstract]. Fall Meeting of the American Geophysical Union. San Francisco, CA. Dec. 5-9, 2011. Abstract #B11C-0504.

Technical Abstract: Nitrate (NO3-) laden agricultural drainage waters are non-point sources of indirect nitrous oxide (N2O) emissions, which represent a significant fraction of total N2O emissions in the USA. On-site denitrification beds filled with woodchips were used to reduce NO3- under carbon rich anaerobic conditions. However, the anaerobic conditions may produce N2O and methane (CH4) to overcome the benefit of NO3- removal. We measured dissolved NO3-, N2O, and CH4 in influents and effluents of denitrification beds as well as soil surface N2O and CH4 fluxes above the bioreactors at two agricultural fields with corn-soybean rotation systems located in the upper Midwest of USA (Dundas and Claremont, Minnesota). Denitrification beds at both sites decrease NO3- from the drainage waters with an average rate of 5.0 g N m-3 d-1 in Dundas and 3.8 g N m-3 d-1 in Claremont. The surface fluxes of N2O and CH4 above the beds were similar to the fluxes measured from adjacent unfertilized fields. Dissolved CH4 in effluents was 38 times and 197 times greater than that in influents in Dundas and Claremont, respectively. Dissolved N2O in effluents was 40% less than that in influents at Dundas, but 15 times greater than that in influents in Claremont. The relationship between effluent to influent ratio of NO3- and hydraulic residence time (HRT) indicated that 50% of NO3- reduction requires 1.1 d in Dundas and 2.3 d in Claremont, although an average HRT was 2.1 d in Dundas and 0.6 d in Claremont. Balance of estimated global warming potential (GWP) indicated that denitrification bed in Claremont increased GWP by 138 g CO2 eq. ha-1 d-1, however, denitrification beds in Dundas reduced GWP by 151 g CO2 eq. ha-1 d-1. These results suggest that denitrification beds could mitigate indirect greenhouse gas emissions if hydraulic residence time is long enough, and denitrification process goes to completion, i.e., from NO3 to di-nitrogen.