Relative humidity-dependent evolution of molecular composition ofα-pinene secondary organic aerosol upon heterogeneous oxidation by hydroxyl radicals  

作　　者：Wei Wang Chenxi Li Huayun Xiao Ziyue Li Yue Zhao 

机构地区：[1]School of Environmental Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China

出　　处：《Journal of Environmental Sciences》2025年第2期210-220,共11页环境科学学报(英文版)

基　　金：supported by the National Natural Science Foundation of China (Nos.22022607 and 42005090);the Shanghai Pujiang Program (No.20PJ1407600)。

摘　　要：Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol(SOA)and plays an important role in controlling the abundance,properties,as well as climate and health impacts of aerosols.However,our knowledge on this heterogeneous chemistry remains inadequate.In this study,the heterogeneous oxidation ofα-pinene ozonolysis SOA by hydroxyl(OH)radicals was investigated under both low and high relative humidity(RH)conditions,with an emphasis on the evolution of molecular composition of SOA and its RH dependence.It is found that the heterogeneous oxidation of SOA at an OH exposure level equivalent to 12 hr of atmospheric aging leads to particle mass loss of 60%at 25%RH and 95%at 90%RH.The heterogeneous oxidation strongly changes the molecular composition of SOA.The dimer-to-monomer signal ratios increase dramatically with rising OH exposure,in particular under high RH conditions,suggesting that aerosol water stimulates the reaction of monomers with OH radicals more than that of dimers.In addition,the typical SOA tracer compounds such as pinic acid,pinonic acid,hydroxy pinonic acid and dimer esters(e.g.,C17H26O8 and C19H28O7)have lifetimes of several hours against heterogeneous OH oxidation under typical atmospheric conditions,which highlights the need for the consideration of their heterogeneous loss in the estimation of monoterpene SOA concentrations using tracer-based methods.Our study sheds lights on the heterogeneous oxidation chemistry ofmonoterpene SOA andwould help to understand their evolution and impacts in the atmosphere.

关 键 词：Secondary organic aerosol(SOA) Heterogeneous oxidation Chemical transformation Molecular composition Aerosol water 

分 类 号：O62[理学—有机化学]