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Epoxide pathways improve model predictions of isoprene markers and reveal key role of acidity in aerosol formation
Citation:
Pye, H., R. Pinder, I. Piletic, Y. Xie, S. Capps, Y. Lin, J. Surratt, Z. Zhang, A. Gold, D. Luecken, Bill Hutzell, M. Jaoui, J. Offenberg, Tad Kleindienst, M. Lewandowski, AND E. Edney. Epoxide pathways improve model predictions of isoprene markers and reveal key role of acidity in aerosol formation. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 47(19):11056-11064, (2013).
Impact/Purpose:
The National Exposure Research Laboratory′s (NERL′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:
Isoprene significantly contributes to organic aerosol in the southeastern United States where biogenic hydrocarbons mix with anthropogenic emissions. In this work, the Community Multiscale Air Quality model is updated to predict isoprene aerosol from epoxides produced under both high- and low-NOx conditions. The new pathways explicitly simulate the formation of two key isoprene-derived species, 2-methyltetrols and 2-methylglyceric acid, and these simulations are more consistent with observations than estimates based on semivolatile partitioning. The new mechanism represents a significant source of organic carbon in the lower 2 km of the atmosphere and captures the abundance of 2-methyltetrols relative to organosulfates during the simulation period. For the parameterization considered here, a 25% reduction in SOx emissions effectively reduces isoprene aerosol while a similar reduction in NOx leads to small increases in isoprene aerosol.
URLs/Downloads:
FINAL FINAL _PYE_ISOP_FULL_R1.PDF (PDF, NA pp, 6536.648 KB, about PDF)Environmental Science & Technology
