Linking hydrological and biogeochemical ‘hot moments’ to take the Aquatic Pulse

Much of the Aquatic Pulse finds its origin in surface and subsurface hydrological pulsations in watersheds. Biogeochemical process reactivity has often been assumed to be slow relative to hydrological flashiness. Until now, there has been little research specifically looking at the linkage between biogeochemical to hydrological ‘hot moments’. More and more evidence suggest that this untapped cross-disciplinary research may unveil over-looked, yet possibly fundamental processes, at the source of the much of the aquatic pulse. For example, riparian buffers have been known for decades as natural hot spots for denitrification to remove from groundwater excess nitrogen produced by agriculture. The intermittent and pulsed nature of hydrology dictates that a majority of the water and nitrate fluxes be transported through the riparian zones in a minority of the time, leaving little exposure time for denitrification to occur. To explain the water quality benefits of riparian zones observed over decades, ‘hot moments’ of denitrification rates must specifically occur during the pulses of flow and nitrate. To test this hypothesis, we conducted experiments in a denitrification bed where we simulated pulses of flow and nitrate concentrations. Results show that in this system, denitrification rates were largely enhanced (x2 to x4) minutes after wetting and drying cycles and sustained for 1-2 days. These results, with others in the literature suggest that linking hydrological and biogeochemical ‘hot moments’ should be investigated and may explain to a significant extent the Aquatic Pulse.

Presentation Preference: Oral

Primary Presenter: François Birgand, North Carolina State University (birgand@ncsu.edu)

Authors:

François Birgand, North Carolina State University  (birgand@ncsu.edu)

Nora Sauers, North Carolina State University  (nlsauers@ncsu.edu)

Adam Rok, Duke University  (adam.rok@duke.edu)

Isaac Hedges, North Carolina State University  (ihedges@ncsu.edu)