Products and mechanisms of ozone reactions with oleic acid for aerosol particles having core-shell morphologies
Journal
Journal of Physical Chemistry A
Journal Volume
108
Journal Issue
32
Pages
6686-6695
Date Issued
2004
Author(s)
Katrib, Y.
Martin, S. T.
Rudich, Y.
Zhang, H. Z.
Slowik, J. G.
Davidovits, P.
Jayne, J. T.
Worsnop, D. R.
Abstract
Heterogeneous reactions of oleic acid aerosol particles with ozone are studied below 1% relative humidity. The particles have inert polystyrene latex cores (101-nm diameter) coated by oleic acid layers of 2 to 30 nm. The chemical content of the organic layer is monitored with increasing ozone exposure by using an aerosol mass spectrometer. The carbon-normalized percent yields of particle-phase reaction products are 20−35% 9-oxononanoic acid, 1−3% azelaic acid, 1−3% nonanoic acid, and 35−50% other organic molecules (designated as CHOT). There is approximately 25% evaporation, presumably as 1-nonanal. To explain the formation of CHOT molecules and the low yields of azelaic and nonanoic acids, we suggest a chemical mechanism in which the Criegee biradical precursors to azelaic acid and nonanoic acid are scavenged by oleic acid to form CHOT molecules. These chemical reactions increase the carbon-normalized oxygen content (z/x) of the CxHyOz layer from 0.1 for unreacted oleic acid to 0.25 after high ozone exposure. Under the assumption that oxygen content is a predictor of hygroscopicity, our results suggest an increased cloud condensation nuclei activity of atmospherically aged organic particles that initially have alkene functionalities.
SDGs
Type
journal article