AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Identifying Precursors and Aqueous Organic Aerosol Formation Pathways in the Humid, Photochemically-Active Southeastern US during the SOAS Campaign
NEHA SAREEN, Annmarie Carlton, Barbara Turpin, Rutgers University
Abstract Number: 248 Working Group: Air Quality and Climate in the Southeast US: Insights from Recent Measurement Campaigns
Abstract Aqueous multiphase chemistry in the atmosphere can lead to rapid transformation of organic compounds, forming highly oxidized low volatility organic aerosol and, in some cases, light absorbing (brown) carbon. Because liquid water is globally abundant, this chemistry could substantially impact climate, air quality, health, and the environment. Gas-phase precursors released from biogenic and anthropogenic sources are oxidized and fragmented forming water-soluble gases that can undergo reactions in the aqueous phase (in clouds, fogs, and wet aerosols) leading to the formation of secondary organic aerosol (SOA$_(AQ)). Recent studies have highlighted the role of certain precursors like glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone, and epoxides in the formation of SOA$_(AQ). The goal of this work is to identify other precursors that are atmospherically important. In this study, ambient mixtures of water-soluble gases were scrubbed from the atmosphere at Brent, Alabama during the Southern Oxidant and Aerosol Study (SOAS). Four mist chambers in parallel collected ambient gases in a DI water medium at 20-25 L/min with a 4 hr collection time. Total organic carbon (TOC) values in daily composited samples were 64-180 micro-M. Aqueous OH radical oxidation experiments were conducted with these mixtures. Results from experiments conducted on two days showed precursors to be primarily odd ions and found in the positive mode by electrospray ionization mass spectrometry (ESI-MS), indicative of the presence of alcohols, aldehydes, organic peroxides, and epoxides. Targeted precursor masses were fragmented using MS/MS to gain structural insights (such as functional groups and O:C and H:C ratios) and identify possible compounds. Products were seen in the negative mode and included pyruvate and oxalate, confirmed using ion chromatography. The results from this study will be used to better understand the precursors and cloud chemistry of these atmospherically relevant mixtures.