Abstract View
Multiphase Ozonolysis of Unsaturated Lipids – Exploring its Mechanism and Product Reactivity
ZILIN ZHOU, Pascale Lakey, Manabu Shiraiwa, Holly Barrett, Hui Peng, Jonathan Abbatt, University of Toronto, Canada
Abstract Number: 167
Working Group: Aerosol Chemistry
Abstract
Unsaturated lipids are commonly found in atmospheric aerosol and on indoor surfaces. It is well known that these lipids decay rapidly under ozone, following the Criegee mechanism. Here, we studied the heterogeneous ozonolysis reactions of oleic acid and their derivatives (esters and triglycerides) on surfaces. The quantitative analyses of the products suggest that, under dry conditions, up to 80% of the products in the condensed phase are secondary ozonides, whose formation is significantly suppressed by elevated relative humidity (RH). This is due to the reaction between Criegee intermediates (CI) and water, forming gas-phase hydrogen peroxide (H2O2) via hydroxyhydroperoxides (α?HHP) intermediates. Such behavior in product composition is well predicted by a kinetic model of triolein (a triglyceride derived form oleic acid). The secondary ozonides derived from triglycerides and phospholipids exhibit high stability in the ambient air and in the aqueous phase. However, mass spectral analyses demonstrate their slow decomposition in ferrous solutions, similar to the Fenton mechanism. Furthermore, an addition of cysteine accelerates the iron redox cycle. The implications of this chemistry will be discussed from the perspectives of oxidative aging of lipids in the environment and potential health effects caused by the oxidation of pulmonary surfactants.