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Impact of dimethylsulfide chemistry on sulfate over the Northern Hemisphere
Citation:
Sarwar, G., K. Fahey, K. Foley, B. Gantt, D. Luecken, AND R. Mathur. Impact of dimethylsulfide chemistry on sulfate over the Northern Hemisphere. CMAS, Chapel Hill, NC, October 05 - 07, 2015.
Impact/Purpose:
The National Exposure Research Laboratory’s Atmospheric Modeling 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:
Sulfate aerosol forms from the gas- and aqueous-phase oxidation of sulfur dioxide and is an important component of atmospheric aerosols. Dimethylsulfide (DMS) present in sea-water can be emitted into the atmosphere which can then react with atmospheric oxidants to produce sulfur dioxide leading to sulfate formation. The current Community Multiscale Air Quality (CMAQ) model, however, does not include DMS emissions and its atmospheric chemistry. In this study, we implement a DMS emission scheme and its atmospheric chemistry into the CMAQ model. DMS emissions are calculated based on oceanic climatological DMS concentrations and the total resistance to gas-transfer at the air/sea interface. Our CMAQ-predicted DMS fluxes are similar to previous estimates reported in the literature. The updated atmospheric chemistry in CMAQ includes gas-phase oxidation of DMS by hydroxyl radical, nitrate, chlorine radical, chlorine monoxide, iodine monoxide, and bromine monoxide. Model simulations without and with the DMS chemistry over the Northern Hemisphere show enhanced concentrations of sulfur dioxide over marine environments. Preliminary results suggest that the inclusion of DMS chemistry enhances sulfate aerosol over marine environments and coastal areas. However, the magnitude of its impact has substantial spatial and temporal variation. The paper will detail the spatial impact of DMS on sulfate concentration and compare model predictions with observed data.
