Secondary Organic Aerosol Production across Worldwide Megacities and Its Impact on Mortality
Abstract
Organic aerosol (OA) is an important fraction of the submicron aerosol budget over urban areas around the world. In these regions, substantial and rapid secondary OA (SOA) production is observed and accounts for 75% of OA in all megacities studied to date. However, multiple studies over different megacities have shown that SOA formation cannot be accounted for when only considering traditional volatile precursor compounds (e.g., aromatics). Either other sources of SOA, including semi-volatile and intermediate-volatile anthropogenic organic compounds (S/IVOCs), or much higher SOA yields for the VOC precursors are needed to account for the observed urban SOA production.
Using data from major megacity field studies (Houston, Mexico City, Los Angeles, Paris, London, Beijing, Seoul, New York City/Boston, and Tokyo), we further explore the photochemical aspects and the importance of S/IVOCs to urban SOA production. We find differences in the SOA production efficiency for these megacities that appear to be driven by differences in precursor emissions across cities. These differences are remarkably consistent with differences in secondary gaseous photochemical species (ozone, formaldehyde, and peroxy acetyl nitrate). S/IVOC emissions are likely to be a major contributor to SOA across all megacities. Finally, we use our results to model globally-realistic urban SOA concentrations, which we use to explore the impacts of urban SOA production on global human mortality. With a sensitivity analysis (removing SOA from GEOS-Chem), we find that urban SOA accounts for 15% of PM2.5 deaths per year. The largest total reductions in mortality occur in South and East Asia, but with the largest relative reduction in mortality occur over North America.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A32E..01N
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0315 Biosphere/atmosphere interactions;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE