| Air pollution is responsible for many adverse effects associated with human health, visibility and ecosystems (aquatic and terrestrial). The Southern Appalachian Mountains Initiative (SAMI) was created to assess the benefits of emission control strategies that could be used to mitigate air quality-related impacts from ozone, aerosols, and acid deposition on the Class I areas of the Southern Appalachian Mountains. A comprehensive three-dimensional Eulerian photochemical model (URM-1ATM) was developed for SAMI as part of their regional effects modeling assessment to quantify the response of pollutant levels to emission control strategies. This is the first time a comprehensive “one-atmosphere” model has been used for an integrated analysis.; The model simulates gas and size-resolved aerosol concentrations of pollutants in the atmosphere and both wet and dry deposition. In this study, the Regional Atmospheric Modeling System (RAMS) and the Emissions Modeling System (EMS-95) are used to generate meteorological and emission input files, respectively. The modeling system is applied to simulate the evolution, transport, and removal of atmospheric pollutants over the Eastern U.S. for nine week-long episodes between 1991 and 1995.; The performance of the model in predicting ozone, size- and composition-resolved aerosols, and wet and dry deposition mass fluxes is evaluated using measurements during each episode. Model performance for ozone are typically within EPA guidance criteria for urban-scale modeling.{09}The major constituents of PM 2.5 (sulfate, ammonium, and organics) each had a mean normalized error of approximately 40%. The mean normalized errors for sulfate and nitrate wet deposition were less than 25%, and dry deposition was typically over-predicted. Most pollutants showed a systematic overestimation for low levels and an underestimation for high levels.; Three different emission control strategies for two future years (2010 and 2040) were modeled to assess how air quality will respond to emission changes. Ozone can be reduced with NOx controls. Sulfate aerosols and sulfur deposition decrease significantly in the Class I areas in response to SO2 emission controls. However, an increase in nitrate and ammonium aerosol levels may result due to an increased availability of ammonia gas in response to reductions in SO2 emissions and increases in NH 3 emissions. Also, changes in total nitrogen deposition were minimal, except when ammonia emissions are controlled.; Finally, a direct sensitivity analysis technique (DDM-3D) within URM-1ATM is used to efficiently determine the impacts of emission reductions from different source regions on atmospheric pollutant levels. Specifically, the impact of SO2 emission reductions on aerosol and wet deposition levels at ten Class I areas is discussed. In general, sulfate aerosol concentrations were reduced by 4%–7% in response to a 10% reduction in domain-wide SO2 emissions. Nitrate increased by 1%–4%, ammonium decreased by 2%–4%, and PM2.5 decreased by 2%–3% in response to a 10% reduction in SO2 emissions. Sulfate wet deposition showed similar reductions to SO2 emissions as sulfate aerosols, but the geographic distribution was more local. |
