A global perspective on aerosol from low-volatility organic compounds H. O. T. Pye and J. H. Seinfeld Department of Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
Abstract. Global production of organic aerosol from primary emissions of semivolatile (SVOCs) and
intermediate (IVOCs) volatility organic compounds is estimated using the global chemical
transport model, GEOS-Chem. SVOC oxidation is predicted to be
a larger global source of net aerosol production than oxidation of traditional parent
hydrocarbons (terpenes, isoprene, and aromatics). Using a prescribed rate constant and
reduction in volatility for atmospheric oxidation, the yield of aerosol from SVOCs is predicted to be
about 75% on a global, annually-averaged basis. For IVOCs, the use of
a naphthalene-like surrogate with different high-NOx and low-NOx
parameterizations produces a global aerosol yield of about 30%, or roughly 5 Tg/yr of aerosol.
Estimates of the total global organic aerosol source presented here range between 60 and
100 Tg/yr. This range reflects uncertainty in the parameters for SVOC volatility, SVOC
oxidation, SVOC emissions, and IVOC emissions, as well as wet deposition. The highest
estimates result if SVOC emissions are significantly underestimated (by more than a factor
of 2) or if wet deposition of the gas-phase semivolatile species is less effective than
previous estimates. A significant increase in SVOC emissions, a reduction of the volatility
of the SVOC emissions, or an increase in the enthalpy of vaporization of the organic aerosol
all lead to an appreciable reduction of prediction/measurement discrepancy. In addition,
if current primary organic aerosol (POA) inventories capture
only about one-half of the SVOC emission and the Henrys Law
coefficient for oxidized semivolatiles is on the order of 103 M/atm, a
global estimate of OA production is not inconsistent with the
top-down estimate of 140 Tg/yr by (Goldstein and Galbally, 2007).
Additional information is needed to constrain the emissions and treatment of SVOCs and
IVOCs, which have traditionally not been included in models.
Citation: Pye, H. O. T. and Seinfeld, J. H.: A global perspective on aerosol from low-volatility organic compounds, Atmos. Chem. Phys., 10, 4377-4401, doi:10.5194/acp-10-4377-2010, 2010.