Size distributions of dicarboxylic acids, ketoacids, α-dicarbonyls, sugars, WSOC, OC, EC and inorganic ions in atmospheric particles over Northern Japan: implication for long-range transport of Siberian biomass burning and East Asian polluted aerosols
1Institute of Low Temperature Science, Hokkaido University, Kita 19, Nishi 8, Sapporo – 0600819, Japan
*now at: National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi – 110012, India
**now at: Japan Isotope Analysis Laboratory, Inc., 75-1 Onocho, Tsurumi-ku, Yokohama-city, Kanagawa 230-0046, Japan
Abstract. To better understand the size-segregated chemical composition of aged organic aerosols in the western Pacific rim, day- and night-time aerosol samples were collected in Sapporo, Japan during summer 2005 using Andersen impactor sampler with 5 size bins: <1.1, 1.1–2.0, 2.0–3.3, 3.3–7.0, >7.0 μm. Samples were analyzed for the molecular compositions of dicarboxylic acids, ketoacids, α-dicarbonyls, and sugars, together with water-soluble organic carbon (WSOC), organic carbon (OC), elemental carbon (EC) and inorganic ions. Based on the analyses of backward trajectory and chemical tracers, we found that during campaign, the air masses were arrived from Siberia (biomass burning source region) on 8–9 August, China (anthropogenic source region) on 9–10 August and from the East China Sea/Sea of Japan (a mixed source receptor region) on 10–11 August. Most of the diacids, ketoacids, dicarbonyls, levoglucosan, WSOC, and inorganic ions, i.e., SO42−, NH42+ and K+ were enriched in fine particles (PM1.1) whereas Ca2+, Mg2+ and Cl− peaked in coarse sizes (>1.1 μm). Interestingly, OC, most sugar compounds and NO4 showed bimodal distributions on fine and coarse modes. In PM1.1, diacids in biomass burning-influenced aerosols from Siberia (mean: 252 ng m−3) were more abundant than those in the aerosols from China (209 ng m−3) and ocean (142 ng m−3) whereas SO42− concentrations maximized in the aerosols from China (mean: 3970 ng m−3) followed by marine- (2946 ng m−3) and biomass burning-influenced (1978 ng m−3) aerosols. Higher loadings of WSOC (2428 ng m−3) and OC (4358 ng m−3) were found on the fine mode, where biomass-burning products such as levoglucosan is abundant. This paper presents a case study that biomass burning episodes in Siberian region have a significant influence on the chemical composition of carbonaceous aerosols in the western North Pacific rim.