Formation of cloud condensation nuclei by oxidative processing: Unsaturated fatty acids

The ability of submicron oleic acid and linoleic acid particles, or condensation nuclei (CN), to act as cloud condensation nuclei (CCN) has been investigated using a tandem differential mobility analyzer (TDMA) coupled to a flow tube reactor and a thermal gradient diffusion chamber (TGDC). The size change and CCN properties of pure oleic acid, mixed oleic acid/methanol, and pure linoleic acid particles have been investigated as a function of exposure to ozone. Pure oleic and linoleic acid particles were CCN inactive for all particle diameters (≤300 nm) and supersaturations (≤1%) studied. The mixed oleic acid/methanol particles, however, had a critical activation diameter of 188 nm for an experimental water supersaturation of 0.6%. Under low ozone exposures (