AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Hydrogen Peroxide Enhances the Heterogeneous Oxidation of Oxygenated Volatile Organic Compounds on Mineral Dust
Yue Zhao, ZHONGMING CHEN, Dao Huang, Peking University
Abstract Number: 554 Working Group: Aerosol Chemistry
Abstract Heterogenous oxidation of oxygenated volatile organic compounds (OVOCs) serves as an important sink of OVOCs as well as a source of secondary organic aerosol. However, the oxidant sources and roles in these reactions are poorly understood. In this work, we present the first laboratory study of the heterogeneous reactions of methacrolein (MACR), an atmospherically important OVOC, on various mineral dust particles (i.e., kaolinite, alpha-Fe2O3, TiO2, and CaCO3) in the presence and absence of gaseous H2O2, with an emphasis on the role of H2O2 in the heterogeneous oxidation of MACR. It is found that the presence of gaseous H2O2 significantly promote both the uptake and chemical transformation of MACR on kaolinite, alpha-Fe2O3, and TiO2 but not on CaCO3. The organic acids were observed as the major low-molecular-weight products,and their yields increase several times in the presence of H2O2. Moreover, organic peroxides such as methyl hydroperoxide, peroxyformic acid, and peroxyacetic acid are only formed in the presence of H2O2, and the formation of methyl hydroperoxide indicates that the oxidation of MACR on the surface involves, at least in part, its reaction with OH radicals. A probing reaction verified the formaiton of OH radicals from H2O2 decomposition on kaolinite, alpha-Fe2O3, and TiO2, which is expected to account for the enhanced oxidation of MACR on kaolinite, alpha-Fe2O3, and TiO2. These results suggest that H2O2 would serve as a source of OH radicals on mineral dust particles and thus may favor the oxidation of co-existing organic compounds. Our findings would extend our understanding on the heterogeneous chemistry of organic compounds on mineral dust, and also highlight the need to investigate the heterogeneous chemistry involving multiple reactive gases.