Closing the Regional Ammonia and Nitrous Oxide Budgets of an Intensive Agricultural Region

Agricultural intensification is increasing the emissions of ammonia and nitrous oxide that are altering regional atmospheric chemistry and global climate, respectively. The US Corn Belt is one of the five major ammonia hotspot observed by satellites largely from the high density of large cattle and swine operations there. The emitted ammonia can deposit on soils downwind and this can promote nitrous oxide production. The proposal will integrate measurements and modeling to quantify how ammonia fluxes amplify nitrous oxide emissions in the continental US. The science will help develop best practices that are sustainable in the future.

The research focus on analysis of ammonia fluxes and nitrous oxide exchange at natural and agricultural systems improve the mechanistic understanding model representations of these processes. The proposal focuses on the following tasks: (1) High precision and near-continuous measurement of ammonia at the University of Minnesota Tall Tower Trace Gas Observatory and using the results for model validation of its source transport and deposition; (2) Perform intensive field campaigns to characterize the landscape in the context of bi-directional NH3 exchange. (3) Simulate high-resolution atmospheric Nr deposition using regional and global models for constraining the soil nitrogen cycling and nitrous emissions. The models will be evaluated against the high-density data sets prior to their use for high-resolution regional scale deposition and nitrous oxide emission modeling. The research will test hypotheses that ammonia deposition impacts regional nitrous oxide emissions and determine constrained emission factors for this volatization in regional (continental US) models.