Aerosol characterisation at the FEBUKO upwind station Goldlauter (Ⅱ): Detailed organic chemical characterisation

摘要

An extensive set of gaseous and particulate organic compounds was quantified before an orographic cloud passage at the upwind site of the research region in Thueringer Wald. Samples were collected with two different time resolutions, 2 h for gaseous species and spray absorber samples and the whole cloud event duration to determine the concentrations of ketones, aldehydes, monocarboxylic acids, dicarboxylic acids (DCA), hydrocarbons, biogenic sugars and alcohols in both the gas and particle phase. The measurement of different groups of organic compounds delivered size-segregated concentrations at the upwind site of a cloud experiment. The size distribution of DCA showed a peak in the mass-rich impactor stage 3 (0.42-1.2 μm). The concentrations of DCA from the filters, the impactor foils as well as the spray absorber samples decreased with increasing C-number. The time resolved measurements revealed an increasing mixing ratio from night time to midday for carboxylic and DCA, and related carbonyl compounds. The biogenic compounds xylitol (up to 103 ng m~(-3)), levoglucosan (up to 62 ng m~(-3)) and pinonaldehyde (up to 34 ng m~(-3)) were the compounds found in highest concentrations in the particle phase beside the oxalate (up to 104 ng m~(-3)). The organic trace gases with the highest mixing ratios identified were formaldehyde (up to 1.47 ppbv), acetaldehyde (up to 0.84 ppbv) and acetone (up to 0.65 ppbv), acetic acid (up to 0.43 ppbv) and formic acid (up to 0.41 ppbv).