10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Tracking Carbon during the Formation of Secondary Organic Aerosol from Alkane Oxidation
JOSHUA MOSS, Abigail Koss, Jesse Kroll, MIT
Abstract Number: 1644 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosol (SOA) comprises a major fraction of particulate matter in the atmosphere and is principally formed via the oxidation of volatile organic compounds (VOCs). This study is primarily focused on understanding SOA formation and evolution from alkanes, likely to be key contributors to particulate matter in urban environments. In general, laboratory chamber studies aimed at elucidating the underlying chemical mechanisms pertaining to SOA formation and evolution have been unable to enumerate all organic species produced in SOA-forming reactions, largely due to the extreme chemical complexity of the system. Alkane chamber studies are challenging also because their relatively slow oxidation rates make it difficult to understand later-generation aging chemistry. Additionally, understanding SOA yields and formation mechanisms from chamber studies can be challenging due to poorly-constrained depositional losses of vapors to chamber walls. Despite substantial study in recent years, these remain uncertain and difficult to predict, varying from species to species and even from chamber to chamber. Such vapor losses may also decrease SOA yields in chamber studies and could contribute to differences in the chemistry observed in chambers from that observed in the atmosphere. Here we describe the results of a series of chamber experiments designed to probe the underlying mechanisms related to alkane SOA formation and evolution. We employ a suite of analytical instruments to perform detailed chemical analysis of alkane oxidation products in conjunction with a technique to measure Total Suspended Carbon (TSC) enabling the direct quantification of wall losses and providing a new constraint on the extent of “carbon balance” measured in atmospheric oxidation studies. These chamber photo-oxidation experiments provide a mechanistic understanding of alkane SOA aging, as well as insights to the role of wall losses of various oxidation products. Additionally, we make direct comparisons between the “bottom-up” measurements obtained from the suite of gas- and particle-phase instruments and the “top-down” constraint imposed by the TSC instrument to understand how wall losses affect SOA formation and aging in chambers.