1 research outputs found
Secondary Organic Aerosol Formation and Chemistry from the OH-Initiated Oxidation of Monofunctional C<sub>10</sub> Species
The formation of secondary organic aerosol (SOA), even
from a simple
hydrocarbon, is a complex, heterogeneous, multigenerational process
involving hundreds of radical intermediate isomers and reaction pathways.
Here, we compared the SOA generated from the reaction of the OH radical
with five precursor species that differed in the identity of their
primary functional group: n-decane, cyclodecane,
2-decanol, 2-decylnitrate, and 2-decanone. We compared results from
smog chamber experiments and an explicit oxidation/gas-particle partitioning
model of first-generation oxidation chemistry (Framework for 0-Dimensional
Atmospheric Modeling–Washington Aerosol Module, F0AM-WAM) under
two NOx regimes: lower NOx where RO2 + HO2 dominates
and higher NOx where RO2 +
NO dominates. Our results show that while functional group identity
impacted the vapor pressures of the precursor species, this alone
was unable to explain trends in experimental yields. Functional groups
also directed the site of initiation with the OH radical and the propagation
and termination reactions that follow, with the most significant differences
noted for 2-decanol. SOA production was greater in the lower NOx experiments for n-decane,
2-decanol, 2-decylnitrate, and 2-decanone due to production of the
low volatility hydroperoxides and oxidized hydroxycarbonyls. Cyclodecane,
however, produced more aerosol in higher NOx experiments, potentially due to the enhanced formation of
low volatility acetals or dimers in the presence of greater concentrations
of nitric acid. Finally, we predicted that as much as 67% of the first-generation
products may undergo subsequent oxidation to later-generation species.
While model results from first-generation chemistry alone are unable
to predict experimentally observed yields and chemistry, this work
provides a foundation for the incorporation of additional (e.g., later-generation
or heterogeneous oxidation chemistry, condensed-phase reactions, etc.)
processes