Serious air pollution problems have arisen frequently in
Chinese cities, represented by simultaneous high levels
of ground-level ozone and PM2.5. Volatile organic com-
pounds (VOCs) are important precursors leading to the
formation of ozone and fine particles (Shao et al., 2011).
Among thousands of VOCs species, carbonyl compounds,
mainly aldehydes and ketones, are highly reactive inter-
mediates during the photo-oxidation of hydrocarbons and
serve as one of the major sources of free radicals (Singh
et al., 1995; Shao et al., 2009). Also, most carbonyls
are irritant and toxic. Formaldehyde and acrolein were
acknowledged as carcinogen by US EPA and WHO.
However, the understanding of carbonyl sources is far