Monoterpenes are the largest source of summertime organic aerosol in the southeastern United States
Citation:
Zhang, H., L. Yee, B. Lee, M. Curtis, D. Worton, G. Isaacman-VanWertz, J. Offenberg, M. Lewandowski, Tad Kleindienst, M. Beaver, A. Holder, Bill Lonneman, K. Docherty, M. Jaoui, H. Pye, W. Hu, D. Day, P. Campuzano-Jost, J. Jimenez, H. Guo, R. Weber, J. de Gouw, A. Koss, E. Edgerton, W. Brune, C. Mohr, F. Lopez-Hilfiker, A. Lutz, N. Kreisberg, S. Spielman, S. Hering, K. Wilson, J. Thornton, AND A. Goldstein. Monoterpenes are the largest source of summertime organic aerosol in the southeastern United States. PNAS (PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES). National Academy of Sciences, WASHINGTON, DC, 9:2038-2043, (2018).
Impact/Purpose:
Atmospheric fine organic aerosol impacts air quality, climate, and human health. Speciating and quantifying the sources of organic aerosol on the molecular level improves understanding of their formation chemistry and hence the resulting impacts. Such study, however, has not been possible due to the chemical complexity of atmospheric organic aerosol. Here, we provide comprehensive molecular characterization of atmospheric organic aerosol samples from the southeastern United States by combining state-of-the-art high-resolution mass spectrometry techniques. We find that monoterpene secondary organic aerosol accounts for approximately half of total fine organic aerosol. More importantly, the monoterpene secondary organic aerosol mass increases with enhanced nitrogen oxide processing, indicating anthropogenic influence on biogenic secondary organic aerosol formation.
Description:
The chemical complexity of atmospheric organic aerosol (OA) has caused substantial uncertainties in understanding its origins and environmental impacts. Here, we provide constraints on OA origins through compositional characterization with molecular-level details. Our results suggest that secondary OA (SOA) from monoterpene oxidation accounts for approximately half of summertime fine OA in Centreville, AL, a forested area in the southeastern United States influenced by anthropogenic pollution. We find that different chemical processes involving nitrogen oxides, during days and nights, play a central role in determining the mass of monoterpene SOA produced. These findings elucidate the strong anthropogenic–biogenic interaction affecting ambient aerosol in the southeastern United States and point out the importance of reducing anthropogenic emissions, especially under a changing climate, where biogenic emissions will likely keep increasing.
