Articles | Volume 16, issue 10
Research article
25 May 2016
Research article |  | 25 May 2016

Aircraft observations of water-soluble dicarboxylic acids in the aerosols over China

Yan-Lin Zhang, Kimitaka Kawamura, Ping Qing Fu, Suresh K. R. Boreddy, Tomomi Watanabe, Shiro Hatakeyama, Akinori Takami, and Wei Wang

Abstract. Vertical profiles of dicarboxylic acids, related organic compounds and secondary organic aerosol (SOA) tracer compounds in particle phase have not yet been simultaneously explored in East Asia, although there is growing evidence that aqueous-phase oxidation of volatile organic compounds may be responsible for the elevated organic aerosols (OA) in the troposphere. Here, we found consistently good correlation of oxalic acid, the most abundant individual organic compounds in aerosols globally, with its precursors as well as biogenic-derived SOA compounds in Chinese tropospheric aerosols by aircraft measurements. Anthropogenically derived dicarboxylic acids (i.e., C5 and C6 diacids) at high altitudes were 4–20 times higher than those from surface measurements and even occasionally dominant over oxalic acid at altitudes higher than 2 km, which is in contrast to the predominance of oxalic acid previously reported globally including the tropospheric and surface aerosols. This indicates an enhancement of tropospheric SOA formation from anthropogenic precursors. Furthermore, oxalic acid-to-sulfate ratio maximized at altitudes of  ∼  2 km, explaining aqueous-phase SOA production that was supported by good correlations with predicted liquid water content, organic carbon and biogenic SOA tracers. These results demonstrate that elevated oxalic acid and related SOA compounds from both the anthropogenic and biogenic sources may substantially contribute to tropospheric OA burden over polluted regions of China, implying aerosol-associated climate effects and intercontinental transport.

Short summary
Here, based on three aircraft measurements over East Asia, we demonstrate an aqueous-phase mechanism for enhanced SOA production in the troposphere following correlation analysis of oxalic acid in tropospheric aerosols with other measured chemical variables including its precursors and its intermediate as well as biogenic-derived SOA from isoprene, monoterpenes and β-caryophyllene.
Final-revised paper