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Contribution of Isoprene Epoxydiol to Urban Organic Aerosol: Evidence from Modeling and Measurements
Karambelas, A., H. Pye, S. Budisulistiorini, J. Surratt, AND R. Pinder. Contribution of Isoprene Epoxydiol to Urban Organic Aerosol: Evidence from Modeling and Measurements. Environmental Science & Technology Letters. American Chemical Society, Washington, DC, 1(6):278-283, (2014).
In a region heavily influenced by anthropogenic and biogenic atmospheric emissions, recent field measurements have attributed one third of urban organic aerosol by mass to isoprene epoxydiols (IEPOX). These aerosols arise from the gas phase oxidation of isoprene, the formation of IEPOX, the reactive uptake of IEPOX by particles, and finally the formation of new compounds in the aerosol phase. Using a continental-scale chemical transport model, we find a strong temporal correspondence between the simulated formation of IEPOX-derived organic aerosol and these measurements. However, because only a subset of isoprene-derived aerosol compounds have been specifically identified in laboratory studies, our simulation of known IEPOX-derived organic aerosol compounds predicts a mass 10-fold lower than the field measurements, despite abundant gas phase IEPOX. Sensitivity studies suggest that increasing the effective IEPOX uptake coefficient and including aerosol-phase reactions that lead to the addition of functional groups could increase the simulated IEPOX-derived aerosol mass and account for the difference between the field measurements and modeling results.
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.
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Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LAB
ATMOSPHERIC MODELING DIVISION
APPLIED MODELING RESEARCH BRANCH