Measurement of carbonyl compounds in Beijing ambient air and rain

The levels of carbonyl compounds in Beijing ambient air and rain were measured from June 2005 to August 2005. Acetone was found to be the most predominant carbonyls followed by formaldehyde, acetaldehyde, propionaldehyde with the mean concentrations of 22.14、19.51、17.18、3.85 μg·m -3 , respectively, which accounted for 84.7% of total carbonyl compounds in the atmosphere. The ratios of formaldehyde to acetaldehyde and acetaldehyde to propionaldehyde indicated that carbonyl compounds in Beijing air mainly originated from anthropogenic sources. The comparison of diurnal profiles in sunny and cloudy conditions demonstrated that the photooxidation of hydrocarbons might play an important role in the formation of carbonyl compounds in summer. Carbonyl concentrations in the air were greatly reduced after rain, indicating that rain is an important sink for carbonyls. Among the 11 carbonyl compounds detected in the rain samples, the most abundant carbonyls were formaldehyde, followed by acetaldehyde and acetone with concentrations of 166.3 μg·L -1 ,43.63 μg·L -1 and 34.33 μg·L -1 , respectively.