SOURCE AND REACTION PATHWAYS OF DICARBOXYLIC-ACIDS, KETOACIDS AND DICARBONYLS IN ARCTIC AEROSOLS - ONE-YEAR OF OBSERVATIONS

Normal saturated (C-2-C-11) and unsaturated (C-4-C-5, C-8) dicarboxyli c acids were measured in arctic aerosol samples collected weekly at Al ert, Canada in 1987-1988. In all seasons, oxalic (C-2) acid was usuall y the dominant diacid species (1.8-70 ng m(-3), av. 14 +/- 12 ng m(-3) ) followed by malonic (C-3; 0.05-19 ng m(-3), av. 2.5 +/- 3.3 ng m(-3) ) and succinic (C-4; 0.51-18 ng m(-3), av. 3.8 +/- 3.5 ng m(-3)) acids . The total concentrations of dicarboxylic acids showed a seasonal var iation (4.3-97 ng m(-3), av. 25 +/- 20 ng m(-3)), with two maxima in S eptember to October and in March to April. The autumn peak is characte rized by high concentrations of oxalic acid and azelaic (C-9) acids, w hich were probably caused by enhanced contributions from anthropogenic and biogenic sources, respectively, followed by photochemical reactio ns. This is consistent with higher concentrations of n-alkanes from te rrestrial plant waxes and of soil-derived aluminum in the autumn aeros ol samples. On the other hand, during ''Arctic Sunrise'' in March to A pril, oxalic, malonic and succinic acids as well as some other (C-5-C- 6) diacids were 5 to 20 times more abundant than in the preceding dark winter months, suggesting that diacids are produced ill situ by secon dary photochemical oxidation of organic pollutants carried to the Arct ic. omega-Oxocarboxylic acids (C-2-C-5, C-9), pyruvic acid and alpha-d icarbonyls (methylglyoxal and glyoxal) were also detected in the arcti c aerosols. Their concentration also showed spring maxima; however, th ey were observed a few weeks earlier than the spring peak of diacids. The omega-oxoacids are likely intermediates to the production of alpha ,omega-dicarboxylic acids at the polar sunrise.