Rethinking organic aerosols: semivolatile emissions and photochemical aging.
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.
Robinson
Allen L
AL
Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213, USA. alr@andrew.cmu.edu
Donahue
Neil M
NM
Shrivastava
Manish K
MK
Weitkamp
Emily A
EA
Sage
Amy M
AM
Grieshop
Andrew P
AP
Lane
Timothy E
TE
Pierce
Jeffrey R
JR
Pandis
Spyros N
SN
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
D000336:Aerosols; D000393:Air Pollutants; D006838:Hydrocarbons; D009930:Organic Chemicals; D052638:Particulate Matter; D001335:Vehicle Emissions