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Development and Evaluation of an Ammonia Bi-Directional Flux Model for Air Quality Models
Citation:
PLEIM, J. E., J. Walker, J. O. BASH, AND E. COOTER. Development and Evaluation of an Ammonia Bi-Directional Flux Model for Air Quality Models. Chapter 29, Douw G. Steyn & Silvia Trini Gastelli (ed.), NATO/TIM Air Pollution Modeling and Its Application, XXI. Springer Netherlands, , Netherlands, Series C:169-174, (2011).
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:
Ammonia is an important contributor to particulate matter in the atmosphere and can significantly impact terrestrial and aquatic ecosystems. Surface exchange between the atmosphere and biosphere is a key part of the ammonia cycle. Agriculture, in particular. is a large source of ammonia emitted to the atmosphere, mostly from animal operations and fertilized crops, while dry and wet deposition are the primary sinks of atmospheric ammonia. Although, current air quality models consider all of these source and sink processes, algorithms for emissions from fertilized crops and dry deposition are too simplistic to provide accurate accounting of the net surface fluxes. New modeling techniques are being developed that replace current ammonia emission from fertilized crops and ammonia dry deposition with a bi-directional surface flux model. Comparisons of the ammonia bi-direction flux algorithm to field experiments involving both lightly fertilized soybeans and heavily fertilized corn are presented and discussed. Initial tests and evaluation of CMAQ modeling results for a full year (2002) al 12km grid resolution including implementation of a soil nitrification model and the ammonia bi-directional flux algorithm result in improved NHx wet deposition.