Carbonyl compounds in the ambient air of hazy days and clear days in Guangzhou, China

Carbonyl compounds were measured in ambient air of Guangzhou in both hazy and clear days. Air samples were collected in two separate terms, 17–19th of November (the clear period) and 30th of November to 2nd of December 2005 (the hazy period). The total concentrations of carbonyls detected varied from 48.4 to 121.4 µg m− 3 (with a mean of 92.0 µg m− 3) in the hazy days and from 21.6 to 45.7 µg m− 3 (with a mean of 32.6 µg m− 3) in the clear days. Formaldehyde, acetaldehyde, and acetone were the most abundant carbonyl species in both haze and clear days, while the relative sum of these three compounds in the clear days contributed more than that in the hazy days to the total concentrations of carbonyls (66.0–72.8% vs 42.9–60.5%). The average concentration ratios of formaldehyde/acetaldehyde (C1/C2) were fairly constant between the haze and clear days (0.87 vs 0.84, (µg m− 3)/(µg m− 3); 1.28 vs 1.23, ppbv/ppbv), whereas those of acetaldehyde/propionaldehyde (C2/C3) showed large variations (ranging from 5.93 to 13.0, (µg m− 3)/(µg m− 3); from 7.82 to 18.3, ppbv/ppbv). The results of correlation analysis and principal component analysis indicated that vehicular exhaust might be the major source of carbonyls in the ambient air, with the biogenic emission as the potential source of some high molecular weight carbonyls. Moreover, biomass burning and accumulation of carbonyls might make significant contribution to the enhancement of carbonyls in the hazy days.