AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Laboratory Studies of In-particle Aqueous Oxidation of Organic Species
JESSE KROLL, Kelly Daumit, Anthony Carrasquillo, Rebecca Sugrue, MIT
Abstract Number: 91 Working Group: The Role of Water in Aerosol Chemistry
Abstract The atmospheric aqueous phase (cloud droplets and deliquesced submicron particles) has received considerable attention as a potentially important medium for the oxidation of organic species, and thus for the formation and evolution of organic aerosol. While laboratory studies have shown aqueous-phase oxidation to be an efficient process for the rapid generation of highly oxidized organic species, most studies have been carried out in bulk solution only. As a result, the effect that partitioning between the gas and aqueous phases may have on such oxidation processes is not well understood. Here we describe a series of chamber experiments in which the oxidation of organic species occurs within deliquesced particles, allowing for gas-particle partitioning to occur during the oxidation process. Organic aerosol is generated either by atomization of water-soluble species or by secondary organic aerosol formation (alpha-pinene or isoprene ozonolysis), and in-particle oxidation is initiated by dark Fenton chemistry (FeSO4/H2O2); particle chemistry and mass is monitored using high-resolution aerosol mass spectrometry. In all cases, the particulate organic species undergo dramatic chemical changes upon oxidation, leading to the formation of highly oxidized species (most notably oxalate). In addition, a substantial fraction of the particulate carbon is lost during oxidation, presumably by fragmentation (C-C bond breaking) reactions followed by evaporation. Thus this work shows that aqueous-phase oxidation can lead to the rapid formation, as well as degradation, of highly oxidized organic aerosol; however the atmospheric importance of such processes depends critically upon the concentrations of oxidants (e.g., OH) within the atmospheric aqueous phase, values which are poorly constrained at present.