Organic Geochemical Studies of Polar Aerosols : Long distance transport and photochemical transformation of natural and anthropogenic materials

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Homologous series of low molecular weight dicarboxylic acids (C2-C11) have been measured in the arctic aerosol samples collected from July 1987 to June 1988 in Alert. Oxalic acid (C2) was found as the dominant species followed by malonic (C3) or succinic (C4) acid. At the time of polar sunrise, certain dicarboxylic acids in arctic haze aerosols became 5 to 20 times more abundant than in the preceding dark winter months. Furthermore, they are correlated with tropospheric ozone depletion events marked by particulate bromine. Here, we report, for the first time, homologous series of dicarboxylic acids in the polar atmosphere and discuss the formation of these organic acids in terms of photochemical oxidation of pollutant precursors that reach the Arctic by long range atmospheric transport from midlatitudes.Antarctic aerosols collected at Syowa Station were also studied for water soluble organic compounds. Total carbon and nitrogen were also determined. Succinic (C4) or oxalic (C2) acid was found as the dominant diacid species followed by azelaic (C9), adipic (C6) or malonic (C3) acid. Concentration range of the total diacids was 5.9-88 ngm-3 with an average of 29 ngm-3. Highest concentrations were observed in the summer sample with a predominance of succinic acid (61.5 ngm-3), which comprised of ca. 70% of the total diacids and accounted for 3.5% of total aerosol carbon (1020 ngm-3). The succinic acid (C4) is likely produced by photooxidation fo 4-oxocarboxylic acids, which are present in the atmosphere as intermediates of the photooxidation of unsaturated fatty acids. These results indicate that the antarctic organic aerosols originate from marine-derived lipids and are transformed largely by photochemical oxidations. w-Oxocarboxylic acids (C2-C9,0.36-3.0 ngm-3) also showed the highest concentration in the summer sample, again suggesting a secondarily production in the atmosphere of the Antarctic and Southern Oceans.