10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

Abstract View


Aging of Selected Particulate Organic Markers in Oxidation Flow Reactors

LIN WANG, Mingyi Wang, Lei Yao, Hangfei Chen, Bowen Zhang, Xiaoyu Hu, Fudan University

     Abstract Number: 319
     Working Group: Oxidation Flow Reactor: Development, Characterization, and Application to Aerosols

Abstract
Aging of organic aerosol particles is one of the least understood topics in atmospheric aerosol research. Here, we used self-made oxidation flow tubes at laminar flow conditions to study OH radical or ozone-initiated aging of selected particulate organic markers, including oleic acid, squalane, and squalene. Pure organic particles were generated via homogeneous nucleation by passing an ultrahigh purity nitrogen over an insulated organic standard and subsequent diluting with zero air. Ozone was produced by photolysis of molecular oxygen using a Hg pen-ray lamp, and OH radical was produced by passing a mixed flow of ozone and water vapor through 254 nm light. We examined gaseous and particulate products by a high-resolution time-of-flight chemical ionization mass spectrometer equipped with a Filter Inlet for Gases and AEROsols (FIGAERO-HRToF-CIMS) using the iodide ion (I-) as the reagent ion. Our results indicate that ozonolysis of an unsaturated particulate species is characterized with formation of high-molecular-weight particulate products through reactions of stabilized Criegee intermediates. On the other hand, OH radical-initiated reactions are featured with multiple reaction mechanisms, especially fragmentation and isomization of the main carbon chain. Our study clearly demonstrates the complexity of atmospheric heterogeneous reactions. A detailed understanding of these mechanisms permits accurate treatment of heterogeneous aging processes in global models in order to better understand the evolution of organic aerosols and to constrain their physicochemical properties including carbon oxidation state, hygroscopicity, and CCN activity throughout their atmospheric lifetime.