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Carbonyl compounds are ubiquitous in the atmosphere and either emitted primarily from anthropogenic and biogenic sources or they are produced secondarily from the oxidation of volatile organic compounds. Despite a number of studies about the quantification of carbonyl compounds a comprehensive description of optimised methods is scarce for the quantification of atmospherically relevant carbonyl compounds. The method optimisation was conducted for seven atmospherically relevant carbonyl compounds including acrolein, benzaldehyde, glyoxal, methyl glyoxal, methacrolein, methyl vinyl ketone and 2,3-butanedione. O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) was used as derivatisation reagent and the formed oximes were detected by gas chromatography/mass spectrometry (GC/MS). With the present method quantification can be carried out for each carbonyl compound originating from fog, cloud and rain or sampled from the gas- and particle phase in water. Detection limits between 0.01 and 0.17 μmol L−1 were found, depending on carbonyl compounds. Furthermore, best results were found for the derivatisation with a PFBHA concentration of 0.43 mg mL−1 for 24 h followed by a subsequent extraction with dichloromethane for 30 min at pH = 1. The optimised method was evaluated in the present study by the OH radical initiated oxidation of 3-methylbutanone in the aqueous phase. Methyl glyoxal and 2,3-butanedione were found to be oxidation products in the samples with a yield of 2% for methyl glyoxal and 14% for 2,3-butanedione after a reaction time of 5 h.

Diurnal mixing ratios of aldehydes and ketones were investigated during two joint experiments in summer months to identify biogenic contributions from coniferous forests to tropospheric chemistry. In a Norway spruce forest, the diurnal variation of carbonyl compounds was measured at 12 m (in the treetop) and at 24 m (above the canopy). The main findings of the experiment are that acetone (up to 9.1 ppbv), formaldehyde (up to 6.5 ppbv), acetaldehyde (up to 5.5 ppbv) and methyl ethyl ketone (MEK, up to 1.8 ppbv) were found in highest concentrations. For all major compounds with the exception of MEK, primary emissions are supposed. From α-pinene oxidation, pinonaldehyde was found with its peak concentrations (up to 0.15 ppbv) during the early morning hours. The diurnal variation of concentrations for most other compounds shows maximum concentrations near midday in 2,4-dinitrophenylhydrazine (DNPH) measurements but not for proton-transfer reaction mass spectrometry (PTR-MS) measurements of acetaldehyde and acetone. A clear correlation of carbonyl compound concentration to the radiation intensity and the temperature (R2=0.66) was found. However, formaldehyde did not show distinct diurnal variations. A very high correlation was observed for both heights between mixing ratios of acetaldehyde and acetone (R2=0.84), acetone and MEK (R2=0.90) as well as acetaldehyde and MEK (R2=0.88) but not for formaldehyde and the others. For the most time, the observed carbonyl compound concentrations above the canopy are higher than within the forest stand. This indicates an additional secondary formation in the atmosphere above the forest. The differences of acetone and acetaldehyde mixing ratios detected by DNPH technique and the PTR-MS could not be fully clarified by a laboratory intercomparison.

A quantitative method for the determination of organic acids in atmospheric particles is developed. The method couples a derivatisation step (thermally assisted hydrolysis and methylation) and a Curie point pyrolyser as a thermal desorption technique and gas chromatography–mass spectrometry (CPP-GC–MS). Among the reagents tested (tetramethylammonium hydroxide (TMAH), tetramethylammonium acetate (TMAAc) and phenyltrimethylammonium hydroxide (TMPAH)), the best performance was found using TMAAc as a derivatisation reagent for the reaction time of 4 s at 510 °C as heating temperature. Calibration was performed for a series of fatty acids (FA), dicarboxylic acids (DCA) and terpenoic acids (TA) under these conditions. Coefficients of determination (R2) were between 0.94 and 0.98. Limits of detection (LOD) were in the nanogram-range between 0.1 and 3.6 ng. The method is applied on atmospheric particle samples to obtain the quantification reproducibility and quantification limits. Reproducibility was determined in terms of relative standard deviations (RSD) for ambient aerosol samples collected by a high-volume-sampler (HVS, RSD = 6–45%, n = 10) and a Berner impactor (BI, RSD = 5–34%, n = 10). Based on 24 h sampling time the developed method enables quantification of all three classes of acids for both sampling techniques. Calibration data and presented volume concentrations are compared with literature data. A comparison with an off-line methylation-GC–MS using BF3 as a derivatisation reagent and capillary electrophoresis coupled mass spectrometry (CE-MS) showed a good agreement. Minimal sample preparation is the main advantage of the developed method. Depending on the sensitivity requirements the present method can be a fast and simple alternative to GC–MS techniques with conventional sample preparation steps for semi-volatile organic acids.

An increasing percentage of agricultural land in Germany is used for oil seed plants. Hence, rape has become an important agricultural plant (in Saxony 1998: 12% of the farmland) in the recent years. During flowering of rape along with intensive radiation and high temperatures, a higher production and emission of biogenic VOC was observed. The emissions of terpenes were determined and more importantly, high concentrations of organic carbonyl compounds were observed during this field experiment. All measurements of interest have been carried out during two selected days with optimal weather conditions. It is found that the origin or the mechanism of formation of different group of compounds had strong influence on the day to day variation of their concentrations. The emission flux of terpenes from flowering rape plants was determined to be 16-32 microg h(-1) m(-2) (30-60 ng h(-1) per g dry plant-540-11080 ng h(-1) per plant), in total. Limonene, alpha-thujene and sabinene were the most important compounds (about 60% of total terpenes). For limonene and sabinene reference emission rates (Ms) and temperature coefficients were determined: beta(limonene) = 0.108 K(-1) and Ms = 14.57 microg h(-1) m(-2) beta(sabinene) = 0.095 K(-1) and Ms = 5.39 microg h(-1) m(-2). The detected carbonyl compound concentrations were unexpectedly high (maximum formaldehyde concentration was 18.1 ppbv and 3.4 ppbv for butyraldehyde) for an open field. Possible reasons for these concentrations are the combination of primary emission from the plants induced by high temperature and high ozone stress, the secondary formation from biogenically and advected anthropogenically emitted VOC at high radiation intensities and furthered by the low wind speeds at this time.