Abstract
Abstract. A new denuder-filter sampling technique has been used to investigate the gas/particle partitioning behaviour of the carbonyl products from the photooxidation of isoprene and 1,3,5-trimethylbenzene. A series of experiments was performed in two atmospheric simulation chambers at atmospheric pressure and ambient temperature in the presence of NOx and at a relative humidity of approximately 50%. The denuder and filter were both coated with the derivatizing agent O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBHA) to enable the efficient collection of gas- and particle-phase carbonyls respectively. The tubes and filters were extracted and carbonyls identified as their oxime derivatives by GC-MS. The carbonyl products identified in the experiments accounted for around 5% and 10% of the mass of secondary organic aerosol formed from the photooxidation of isoprene and 1,3,5-trimethylbenzene respectively. Experimental gas/particle partitioning coefficients were determined for a wide range of carbonyl products formed from the photooxidation of isoprene and 1,3,5-trimethylbenzene and compared with the theoretical values based on standard absorptive partitioning theory. Photooxidation products with a single carbonyl moiety were not observed in the particle phase, but dicarbonyls, and in particular, glyoxal and methylglyoxal, exhibited gas/particle partitioning coefficients several orders of magnitude higher than expected theoretically. These findings support the importance of heterogeneous and particle-phase chemical reactions for SOA formation and growth during the atmospheric degradation of anthropogenic and biogenic hydrocarbons.
Highlights
The atmospheric degradation of volatile organic compounds (VOCs) yields a range of oxygenated products that, depending on their physical and chemical properties, can lead to the formation of secondary organic aerosol (SOA)
Photooxidation products with a single carbonyl moiety were not observed in the particle phase, but dicarbonyls, and in particular, glyoxal and methylglyoxal, exhibited gas/particle partitioning coefficients several orders of magnitude higher than expected theoretically
Biogenic and anthropogenic sources of VOCs both contribute to SOA formation
Summary
The atmospheric degradation of volatile organic compounds (VOCs) yields a range of oxygenated products that, depending on their physical and chemical properties, can lead to the formation of secondary organic aerosol (SOA). Biogenic and anthropogenic sources of VOCs both contribute to SOA formation. A considerable amount of information on the SOA-forming potential of individual biogenic and anthropogenic VOCs has been obtained from simulation chamber experiments performed over the last 10 years (Kroll et al, 2006; Ng et al, 2007; Odum et al, 1997). A number of recent studies have utilised state-of-the-art methods to investigate the chemical composition of SOA, in general the overall yield of products detected in the particle phase
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