title: Diurnal and temporal variations of water-soluble dicarboxylic acids and related compounds in aerosols from the northern vicinity of Beijing: implication for photochemical aging during atmospheric transport.
abstract: Aerosol samples were collected in autumn 2007 on day- and nighttime basis in the northern receptor site of Beijing, China. The samples were analyzed for total carbon (TC) and water-soluble dicarboxylic acids (C2-C12), oxocarboxylic acids (C2-C9), glyoxal and methylglyoxal to better understand the photochemical aging of organic aerosols in the vicinity of Beijing. Concentrations of TC are 50% greater in daytime when winds come from Beijing than in nighttime when winds come from the northern forest areas. Most diacids showed higher concentrations in daytime, suggesting that the organics emitted from the urban Beijing and delivered to the northern vicinity in daytime are subjected to photo-oxidation to result in diacids. However, oxalic acid (C2), which is the most abundant diacid followed by C3 or C4, became on average 30% more abundant in nighttime together with azelaic, ω-oxooctanoic and ω-oxononanoic acids, which are specific oxidation products of biogenic unsaturated fatty acids. Methylglyoxal, an oxidation product of isoprene and a precursor of oxalic acid, also became 29% more abundant in nighttime. Based on a positive correlation between C2 and glyoxylic acid (ωC2) in nighttime when relative humidity significantly enhanced, we propose a nighttime aqueous phase production of C2 via the oxidation of ωC2. We found an increase in the contribution of diacids to TC by 3 folds during consecutive clear days. This study demonstrates that diacids and related compounds are largely produced in the northern vicinity of Beijing via photochemical processing of organic precursors emitted from urban center and forest areas.
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-ku, Sapporo 060-0819, Japan; Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Nannan
authors.initials: N
authors.lastname: He
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-ku, Sapporo 060-0819, Japan. Electronic address: kawamura@lowtem.hokudai.ac.jp.
authors.forename: Kimitaka
authors.initials: K
authors.lastname: Kawamura
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-ku, Sapporo 060-0819, Japan; Graduate School of Environmental Science, Hokkaido University, N10 W5, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Okuzawa
authors.affiliation: Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Japan.
authors.forename: P
authors.initials: P
authors.lastname: Pochanart
authors.affiliation: Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kanaya
authors.affiliation: LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Z F
authors.initials: ZF
authors.lastname: Wang
mesh_terms: D000336:Aerosols / Q000032:analysis* / Q000737:chemistry; D000392:Air Movements; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D001272:Atmosphere / Q000737:chemistry; D002681:China; D003998:Dicarboxylic Acids / Q000032:analysis* / Q000737:chemistry; D004784:Environmental Monitoring; D055668:Photochemical Processes
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D003998:Dicarboxylic Acids
keywords: Aqueous-phase production; Dicarboxylic acids; Glyoxylic acid; Organic aerosols; Oxalic acid; Photochemical aging