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

摘要

To better understand the size-segregated chemical composition of aged organic aerosols in the western North Pacific rim, day-and night-time aerosol samples were collected in Sapporo, Japan during summer 2005 using an Andersen impactor sampler with 5 size bins: D_p<1.1, 1.1-2.0, 2.0-3.3, 3.3-7.0, >7.0 μm. Samples were analyzed for the molecular composition 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 trajectories and chemical tracers, we found that during the campaign, air masses arrived from Siberia (a biomass burning source region) on 8-9 August, from China (an 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., SO~(2-)_3, NH~+_4 and K~+) were enriched in fine particles (PM_(1.1)) whereas Ca~(2+), Mg~(2+) and Cl~- peaked in coarse sizes (>1.1 μm). Interestingly, OC, most sugar compounds and NO~-_3 showed bimodal distributions in fine and coarse modes. In PM_(1.1), diacids in biomass burning-influenced aerosols transported from Siberia (mean: 252 ng mg ~(-3)) were more abundant than those in the aerosols originating from China (209 ng mg~(-3)) and ocean (142 ng mg~(-3)), whereas SO~(2-)_4 concentrations were highest in the aerosols from China (mean: 3970 ng mg~(-3)) followed by marine-(2950 ng mg ~(-3)) and biomass burning-influenced (1980 ng mg~(-3)) aerosols. Higher loadings of WSOC (2430 ng mg~(-3)) and OC (4360 ng mg~(-3)) were found in the fine mode, where biomass-burning products such as levoglucosan are abundant. This paper presents a case study of long-range transported aerosols illustrating that biomass burning episodes in the Siberian region have a significant influence on the chemical composition of carbonaceous aerosols in the western North Pacific rim.