Geochemical Journal, Vol. 44 (No. 4), pp. e17-e22, 2010EXPRESS LETTER
Nannan He1,2 and Kimitaka Kawamura2
1Graduate School of Environmental Science, Hokkaido University, N11 W5, Kita-ku, Sapporo 060-0819, Japan
2Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-ku, Sapporo 060-0819, Japan
(Received April 6, 2010; Accepted June 15, 2010; Online published June 24, 2010)
Aerosol samples were collected at Mangshan in the north of Beijing, China in autumn 2007 and analyzed for α, ω-dicarboxylic acids (C2-C12), ketoacids (ωC2- ωC4, ωC9, pyruvic acid) and α-dicarbonyls (glyoxal and methylglyoxal). Oxalic (C2) acid was found as the most abundant species, followed by succinic (C4) and malonic (C3) acids. Concentrations of most compounds, except for C2 and some other species, were higher in daytime than nighttime, indicating that diacids are produced by photochemical oxidation of organic precursors emitted from anthropogenic sources such as fossil-fuel combustion in Beijing, and are transported to Mangshan area by the northerly wind in daytime. Phthalic acid (Ph) was detected as the 4th most abundant diacid both in daytime and nighttime samples, indicating that anthropogenic sources significantly contribute to the organic aerosols. However, lower adipic (C6)/azelaic (C9) acid ratios in nighttime than daytime suggest that biogenic source makes more contribution to the aerosols in nighttime. Higher ratios of C2/total diacids in nighttime than daytime suggest the aging of aerosols proceed more in nighttime, probably due to the aqueous phase oxidation of biogenic precursors. This study demonstrates that water-soluble organic aerosols are secondarily produced in the vicinity of Beijing by the oxidation of both anthropogenic and biogenic precursors.
Key words: dicarboxylic acids, ketoacids, α-dicarbonyls, anthropogenic and biogenic emissions, secondary organic aerosols