COMPARATIVE DISTRIBUTIONS OF DICARBOXYLIC-ACIDS AND RELATED POLAR COMPOUNDS IN SNOW RAIN AND AEROSOLS FROM URBAN ATMOSPHERE

Nine wet precipitation (snow, sleet and rain) and four aerosol samples, collected from Tokyo, were studied for the molecular distributions of dicarboxylic acids and related polar compounds (ketoacids and dicarbonyls) by a capillary gas chromatography (GC) and GC-mass spectrometry. Wet samples were also analysed for dissolved organic carbon (DOC), whereas aerosol samples were studied for total carbon, total nitrogen and water soluble organic carbon. A homologous series of dicarboxylic acids (C2-C9) were detected in both wet precipitation (12-540 mug l-1) and aerosol (1.1-3.0 mug m-3) samples. Although oxalic acid (C2) was generally the dominant diacid species followed by either malonic, succinic or phthalic acid in the samples studied, its relative abundance in total diacids was different between the wet precipitation (34 +/- 8%) and aerosol (51 +/- 5%) samples. These results suggest that oxalic acid is more enriched at near-ground level than upper levels of the troposphere. Time series of precipitation samples showed that diacid carbon concentration normalized by DOC decreased as a function of time during precipitation events. These results suggest that diacids, which exist as particles, are more efficiently scavenged from the atmosphere than other water soluble organic compounds.