FDATMOS16 non-linear partitioning and organic volatility distributions in urban aerosols

Journal Article · Thu Dec 17 00:00:00 EST 2015 · Faraday Discussions

DOI:https://doi.org/10.1039/C5FD00209E· OSTI ID:1245388

Madronich, Sasha ^[1]; Kleinman, Larry ^[2]; Conley, Andrew ^[1]; Lee-Taylor, Julie ^[1]; Hodzic, A. ^[1]; Aumont, Bernard ^[3]

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1. National Center for Atmospheric Research, Boulder, CO (United States)
2. Brookhaven National Lab. (BNL), Upton, NY (United States)
3. CNRS, Univ. Paris Est Creteil et Univ., Creteil (France)

Gas-to-particle partitioning of organic aerosols (OA) is represented in most models by Raoult’s law, and depends on the existing mass of particles into which organic gases can dissolve. This raises the possibility of non-linear response of particle-phase OA to the emissions of precursor volatile organic compounds (VOCs) that contribute to this partitioning mass. Implications for air quality management are evident: A strong non-linear dependence would suggest that reductions in VOC emission would have a more-than-proportionate benefit in lowering ambient OA concentrations. Chamber measurements on simple VOC mixtures generally confirm the non-linear scaling between OA and VOCs, usually stated as a mass-dependence of the measured OA yields. However, for realistic ambient conditions including urban settings, no single component dominates the composition of the organic particles, and deviations from linearity are presumed to be small. Here we re-examine the linearity question using volatility spectra from several sources: (1) chamber studies of selected aerosols, (2) volatility inferred for aerosols sampled in two megacities, Mexico City and Paris, and (3) an explicit chemistry model (GECKO-A). These few available volatility distributions suggest that urban OA may be only slightly super-linear, with most values of the sensitivity exponent in the range 1.1-1.3, also substantially lower than seen in chambers for some specific aerosols. Furthermore, the rather low values suggest that OA concentrations in megacities are not an inevitable convergence of non-linear effects, but can be addressed (much like in smaller urban areas) by proportionate reductions in emissions.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• OSTI ID: 1245388
• Report Number(s): BNL--111945-2016-JA; KP1701000
• Journal Information: Faraday Discussions, Journal Name: Faraday Discussions Journal Issue: 1 Vol. 19; ISSN 1359-6640; ISSN FDISE6
• Publisher: Royal Society of Chemistry
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES