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Estimation of NH3 Bi-Directional Flux from Managed Agricultural Soils
Citation:
COOTER, E., J. O. BASH, J. T. WALKER, JR., M. R. Jones, AND W. Robarge. Estimation of NH3 Bi-Directional Flux from Managed Agricultural Soils. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 44(17):2107-2115, (2010).
Impact/Purpose:
The National Exposure Research Laboratory′s (NERL′s) Atmospheric Modeling and Analysis Division (AMAD) conducts research in support of EPA′s mission to protect human health and the environment. AMAD′s research program is engaged in developing and evaluating predictive atmospheric models on all spatial and temporal scales for forecasting the Nation′s air quality and for assessing changes in air quality and air pollutant exposures, as affected by changes in ecosystem management and regulatory decisions. AMAD is responsible for providing a sound scientific and technical basis for regulatory policies based on air quality models to improve ambient air quality. The models developed by AMAD are being used by EPA, NOAA, and the air pollution community in understanding and forecasting not only the magnitude of the air pollution problem, but also in developing emission control policies and regulations for air quality improvements.
Description:
The Community Multi-Scale Air Quality model (CMAQ v4.7) contains a bi-directional ammonia (NH3) flux option that computes emission and deposition of ammonia derived from commercial fertilizer via a temperature dependent parameterization of canopy and soil compensation point. The research reported here describes the development and testing of enhancements to this treatment to include a process-based dynamic parameterization of an NH3 soil compensation point. This requires the estimation of ammonium and hydrogen ion concentrations in the soil as well as information about current agricultural management practices. A box model based on the nitrification portion of the USDA EPIC (Environmental Policy Integrated Climate) model is calibrated using vegetation canopy and soil chemistry data from a Lillington, NC field study conducted during 2007. We combine these results with measurements of near-surface NH3 concentrations and modeled NH3 flux estimates to evaluate soil NH3 emissions. Our results demonstrate the sensitivity of the model to the estimation of below-canopy friction velocity, laminar boundary resistance and soil resistance, but these terms can be combined to produce model results that agree well with field observations. The box-model flux (emission) results are compared to agricultural management model and national ammonia emission inventory estimates to consider the potential impact and benefit of a domain-wide implementation of the soil compensation point paradigm.
URLs/Downloads:
Estimation of NH3 Bi-Directional Flux from Managed Agricultural Soils (PDF, NA pp, 7519 KB, about PDF)Atmospheric Environment
