Secondary organic aerosol formation from aromatic and biogenic hydrocarbons

The tropospheric oxidation of hydrocarbons by ozone, OH or NO3 radicals leads to the formation of condensable products that can undergo gas-to-particle conversion. We studied the aerosol formation from m-xylene, 1,2,4-trimethylbenzene and several biogenics (mono- and sesquiterpenes as well as oxygenated compounds) in a series of outdoor smog chamber experiments at CalTech, Expressions for the fractional SOA yield (Y) are developed within the framework of a gas/partitioning absorption model and the yield is shown to be a function of the organic aerosol mass concentration. The observations not only suggest that yields for individual hydrocarbons are additive but that smog chamber SOA yields data may confidently extrapolated to the ambient atmosphere.