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Science 2 March 2007:
Vol. 315. no. 5816, pp. 1259 - 1262
DOI: 10.1126/science.1133061
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Reports

Rethinking Organic Aerosols: Semivolatile Emissions and Photochemical Aging

Allen L. Robinson,1* Neil M. Donahue,1* Manish K. Shrivastava,1 Emily A. Weitkamp,1 Amy M. Sage,1 Andrew P. Grieshop,1 Timothy E. Lane,1 Jeffrey R. Pierce,1 Spyros N. Pandis1,2

Most primary organic-particulate emissions are semivolatile; thus, they partially evaporate with atmospheric dilution, creating substantial amounts of low-volatility gas-phase material. Laboratory experiments show that photo-oxidation of diesel emissions rapidly generates organic aerosol, greatly exceeding the contribution from known secondary organic-aerosol precursors. We attribute this unexplained secondary organic-aerosol production to the oxidation of low-volatility gas-phase species. Accounting for partitioning and photochemical processing of primary emissions creates a more regionally distributed aerosol and brings model predictions into better agreement with observations. Controlling organic particulate-matter concentrations will require substantial changes in the approaches that are currently used to measure and regulate emissions.

1 Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
2 Department of Chemical Engineering, University of Patras, Patra 26500, Greece.

* To whom correspondence should be addressed. E-mail: alr{at}andrew.cmu.edu (A.L.R.); nmd{at}andrew.cmu.edu (N.M.D.)

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Evidence for liquid-like and nonideal behavior of a mixture of organic aerosol components.
C. D. Cappa, E. R. Lovejoy, and A. R. Ravishankara (2008)
PNAS 105, 18687-18691
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