资源环境科技发展态势分析平台

The presence of water-soluble dicarboxylic acids in atmospheric aerosols has a significant influence on the regional radiative forcing through direct aerosol effect and cloud formation process. Fine aerosol (PM2.5) samples collected in central Alaska (Fairbanks: 64.51 degrees N and 147,51 degrees W) during summer of 2009 were measured for water-soluble diacids (C-2-C-12), oxoacids (C-2-C-9) and alpha-dicarbonyls (C-2-C-3) as well as elemental carbon (EC), organic carbon (OC) and water-soluble OC (WSOC) to assess their sources and formation processes. We found the predominance of oxalic acid (C-2) followed by malonic (C-3) and succinic acid (C-4) in Alaskan aerosols. Higher C-3/C-4 diacid ratios (ave. 1.2) in Alaskan aerosols than those reported for fresh aerosols emitted from fossil fuel combustion (ave. 0.35) and biomass burning (0.51-0.66) suggest that organic aerosols in central Alaska were photochemically processed. The relatively high correlations of major diacids and related compounds with levoglucosan (r = 0.80-0.99) than those with 2-methylglyceric acid (r = 0.59-0.98) suggest that they were significantly produced from biomass burning emission. Strong correlations of C-2 with normal-chain saturated diacids (C-3-C-9: r = 0.80-0.98), glyoxylic acid (omega C-2: r = 0.95) and methylglyoxal (MeGly: r = 0.88), together with strong correlations of solar radiation with ratio of C-2 to C-2-C-12 diacids (r = 0.83), omega C-2 (r = 0.80) and MeGly (r = 0.82) suggest that oxalic acid in PM2.5 aerosol was produced by the photooxidation of higher homologous diacids, glyoxylic acid and methylglyoxal in the atmosphere of central Alaska. These results reveal that photochemical processing of organic precursors mainly produced from biomass burning control the water-soluble organic chemical composition of fine aerosols in central Alaska.