title: Influence of metal-mediated aerosol-phase oxidation on secondary organic aerosol formation from the ozonolysis and OH-oxidation of α-pinene.
abstract: The organic component is the most abundant fraction of atmospheric submicron particles, while the formation mechanisms of secondary organic aerosol (SOA) are not fully understood. The effects of sulfate seed aerosols on SOA formation were investigated with a series of experiments carried out using a 9 m3smog chamber. The presence of FeSO4or Fe2(SO4)3seed aerosols decreased SOA yields and increased oxidation levels in both ozonolysis and OH-oxidation of α-pinene compared to that in the presence of ZnSO4or (NH4)2SO4. These findings were explained by metal-mediated aerosol-phase oxidation of organics: reactive radicals were generated on FeSO4or Fe2(SO4)3seed aerosols and reacted further with the organic mass. This effect would help to explain the high O/C ratios of organics in ambient particles that thus far cannot be reproduced in laboratory and model studies. In addition, the gap in the SOA yields between experiments with different seed aerosols was more significant in OH-oxidation experiments compared to ozonolysis experiments, while the gap in estimated O/C ratios was less obvious. This may have resulted from the different chemical compositions and oxidation levels of the SOA generated in the two systems, which affect the branching ratio of functionalization and fragmentation during aerosol oxidation.
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.|Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
authors.forename: Biwu
authors.initials: B
authors.lastname: Chu
authors.affiliation: Air Quality Research Division, Environment Canada, Toronto, Ontario M3H5T4, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Liggio
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.|Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yongchun
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.|Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Hong
authors.initials: H
authors.lastname: He
authors.affiliation: Toyota Central Research and Development Laboratory, Nagakute, Aichi 480-1192, Japan.
authors.forename: Hideto
authors.initials: H
authors.lastname: Takekawa
authors.affiliation: Air Quality Research Division, Environment Canada, Toronto, Ontario M3H5T4, Canada.
authors.forename: Shao-Meng
authors.initials: SM
authors.lastname: Li
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Jiming
authors.initials: J
authors.lastname: Hao