Gas/particle partitioning of carbonyls in the photooxidation of isoprene and 1,3,5-trimethylbenzene

R. M. Healy (1) , J. C. Wenger (1) , A. Metzger (2) , J. Duplissy (2) , M. Kalberer (2, 3) , J. Dommen (3)

1 Department of Chemistry and Environmental Research Institute
2 LAC - Laboratory of Atmospheric Chemistry [Paul Scherrer Institute]
3 Department of Analytical Chemistry, Laboratory of Organic Chemistry

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 NO_x 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 chemistry as a pathway for SOA formation and growth during the atmospheric degradation of anthropogenic and biogenic hydrocarbons.

Domaines: Océan, Atmosphère

R. M. Healy, J. C. Wenger, A. Metzger, J. Duplissy, M. Kalberer, et al.. Gas/particle partitioning of carbonyls in the photooxidation of isoprene and 1,3,5-trimethylbenzene. Atmospheric Chemistry and Physics Discussions, 2008, 8 (2), pp.4727-4764. ⟨hal-00304016⟩