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Improvements to the treatment of organic nitrogen chemistry & deposition in CMAQ
Schwede, D., D. Luecken, AND Johnt Walker. Improvements to the treatment of organic nitrogen chemistry & deposition in CMAQ. 2015 American Meteorological Society Meeting, Phoenix, AZ, January 05 - 09, 2015.
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.
Excess atmospheric nitrogen deposition can cause significant harmful effects to ecosystems. Organic nitrogen deposition can be an important contributor to the total nitrogen budget, contributing 10-30%, however there are large uncertainties in the chemistry and deposition of these compounds. Recent measurement studies provide the opportunity for the improvement and evaluation of the treatment of organic nitrogen compounds in the Community Multiscale Air Quality (CMAQ) model. We examine updates to the CB05 chemical mechanism to improve the treatment of organic nitrate compounds and the resulting impact on atmospheric dry and wet deposition as well as the impact on air quality, including ozone concentrations. Our results show that previous versions of CMAQ greatly underestimate the deposition of organic nitrates. Improvements to the speciation as well the solubility of the organic nitrate species are important to correctly predicting the deposition. Comparisons of CMAQ concentration and deposition with measured values are provided to evaluate the model updates.