EGU2020-22205
https://doi.org/10.5194/egusphere-egu2020-22205
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Effects of drying and rewetting cycles on denitrification and greenhouse gas emissions in normally saturated organic substrate

François Birgand1, Bryan Maxwell1, Augustin Thomas2, Louis Schipper3, David Williams4, Laura Christianson5, Shying Tian1, Matthew Helmers6, Chip Chescheir1, and Mohamed Youssef1
François Birgand et al.
  • 1North Carolina State University, Biological and Agricultural Engineering, United States of America (francois_birgand@ncsu.edu)
  • 2Ecole Polytechnique, Paris, France (augustin.thomas@polytechnique.edu)
  • 3NIWA, University of Waikato, Hamilton, New Zealand (schipper@waikato.ac.nz)
  • 4USEPA, Durham, United States of America (Williams.DavidJ@epa.gov )
  • 5Crop Science, University of Illinois, United States of America (lechris@illinois.edu)
  • 6Department of Agricultural and Biosystems Engineering, Iowa State University, United States of America (mhelmers@iastate.edu)

The effects of intermittent drying of normally saturated organic systems such as peatlands, swamps, or wetlands has not been reported quite as often as those of wetting and drying cycles of normally dry soils. We report here the effects of weekly drying and rewetting events on saturated woodchips used as denitrification bed. We used denitrification rates and gas effluxes as indicators of the response of normally saturated organic substrate to intermittent aerobic conditions. We used replicated eight upflow columns in the lab fed with nitrated water, and undergoing variable duration of intermittent aerobic conditions (none, 2, 8, and 24 hours) over a 400d experiment.  We used high-frequency sensors to measure in- and outflow nitrate and DOC concentrations on a 2-hour basis, from which we calculated denitrification rates. We also measured the CO2 and N2O effluxes in the headspace on an hourly basis. The results show a burst of respiration activity during drying events and for several days after rewetting. Isotopic data suggest that respiration was bacterial denitrification. Intermittent aerobic conditions seem to provide the conditions conducive to the generation of more and better quality DOC, which microbes use during subsequent saturated conditions. Our results suggest that intermittent aerobic conditions may have lasting impacts on microbial respiration in wetlands.

How to cite: Birgand, F., Maxwell, B., Thomas, A., Schipper, L., Williams, D., Christianson, L., Tian, S., Helmers, M., Chescheir, C., and Youssef, M.: Effects of drying and rewetting cycles on denitrification and greenhouse gas emissions in normally saturated organic substrate, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22205, https://doi.org/10.5194/egusphere-egu2020-22205, 2020