AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Water-Soluble Dicarboxylic Acids, Ketocarboxylic Acids, Alpha-Dicarbonyls, and Fatty Acids in Association with Biogenic Secondary Organic Aerosol over a Forest Site in Japan
YUEMEI HAN, Kei Nosaka, Yoko Iwamoto, Kaori Kawana, Kimitaka Kawamura, Tomoki Nakayama, Mochida Michihiro, Graduate School of Environmental Studies, Nagoya University
Abstract Number: 696 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Water-soluble organic carbon (WSOC) constitutes a significant proportion of organic aerosol mass in the atmosphere. One important class of WSOC compounds is dicarboxylic acids and other bifunctional compounds, which are originated from primary emission sources and formed secondarily through atmospheric oxidation processes in aqueous phase. Due to their highly hygroscopic nature, the presence of dicarboxylic acids and other bifunctional compounds in the atmosphere may alter the capability of aerosol to retain water and to act as cloud condensation nuclei, thereby affecting hydrological cycles and other climate-related impacts. In this study, samplings of atmospheric aerosol particles (TSP and PM0.95) on quartz fiber filters together with real-time measurements of submicron aerosol particles were performed at a forest site in Wakayama Prefecture, Japan, from 20 to 30 August 2010. The aerosol filter samples were extracted and analyzed for the quantification of dicarboxylic acids, oxocarboxylic acids, alpha-dicarbonyls, and fatty acids using gas chromatography (GC) and GC/mass spectrometry. WSOC accounted for, on average, 30% and 75% of total carbon mass in TSP and PM0.95, respectively. The mean mass concentrations of the quantified organic molecular groups in TSP (or PM0.95) on non-event days were 2.4–14.2 (or 1.8–7.4) times higher than those on new particle formation (NPF) event days. The day/night variations showed that the mass concentrations of the quantified water-soluble organics in the nighttime were close to those in the daytime, which was probably resulted from the partitioning of semivolatile species into the particle phase at high relative humidity and/or from aqueous phase reactions. The relatively low fractions of WSOC in the daytime on NPF event days suggest that freshly formed biogenic SOA was more water-insoluble. Low-volatility oxygenated organic aerosol (LV-OOA) had stronger correlations with WSOC and dicarboxylic acids than semivolatile OOA (SV-OOA), suggesting that LV-OOA was more water-soluble than SV-OOA.