A secondary organic aerosol (SOA) is a molecule produced via oxidation over several generations of a parent organic molecule.[1] In contrast to primary organic aerosols, which are emitted directly from the biosphere, SOAs are either formed via homogeneous nucleation through the successive oxidation of gas-phase organic compounds, or through condensation on pre-existing particles. These gas-phase species exert high vapor pressures, meaning they are volatile and stable in the gas-phase.

Upon oxidation, the increased polarity, and thus reduced volatility, of the molecules results in a reduction of vapor pressure. After sufficient oxidation, the vapor pressure is sufficiently low that the gas-phase compound partitions into the solid-phase, producing secondary organic matter (the particle phase of SOA).

SOAs represent a significant proportion of aerosols contained in the troposphere.[1]

References

  1. ^ a b Yee, Lindsay D.; Craven, Jill S.; Loza, Christine L.; Schilling, Katherine A.; Ng, Nga Lee; Canagaratna, Manjula R.; Ziemann, Paul J.; Flagan, Richard C.; Seinfeld, John H. (2012-06-21). "Secondary Organic Aerosol Formation from Low-NOx Photooxidation of Dodecane: Evolution of Multigeneration Gas-Phase Chemistry and Aerosol Composition" (PDF). The Journal of Physical Chemistry A. 116 (24): 6211–6230. Bibcode:2012JPCA..116.6211Y. doi:10.1021/jp211531h. ISSN 1089-5639. PMID 22424261. S2CID 24782263.

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