title: Rethinking organic aerosols: semivolatile emissions and photochemical aging.
abstract: 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.
authors.affiliation: Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213, USA. alr@andrew.cmu.edu
authors.forename: Allen L
authors.initials: AL
authors.lastname: Robinson
authors.forename: Neil M
authors.initials: NM
authors.lastname: Donahue
authors.forename: Manish K
authors.initials: MK
authors.lastname: Shrivastava
authors.forename: Emily A
authors.initials: EA
authors.lastname: Weitkamp
authors.forename: Amy M
authors.initials: AM
authors.lastname: Sage
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Grieshop
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Lane
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Pierce
authors.forename: Spyros N
authors.initials: SN
authors.lastname: Pandis
mesh_terms: D000336:Aerosols; D000393:Air Pollutants / Q000737:chemistry*; D003198:Computer Simulation; D006838:Hydrocarbons / Q000737:chemistry; D008433:Mathematics; D008956:Models, Chemical; D009930:Organic Chemicals / Q000737:chemistry*; D010084:Oxidation-Reduction; D052638:Particulate Matter / Q000737:chemistry*; D044367:Phase Transition; D010777:Photochemistry; D014466:Ultraviolet Rays; D001335:Vehicle Emissions / Q000032:analysis*; D014835:Volatilization
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D006838:Hydrocarbons; D009930:Organic Chemicals; D052638:Particulate Matter; D001335:Vehicle Emissions