资源环境科技发展态势分析平台

Formaldehyde (HCHO) is an abundant carbonyls and plays important roles in ozone formation and atmospheric oxidizing capacity. To better understand the formation mechanisms of HCHO and its effects on ozone formation, carbonyl compounds were measured at a regional background site of Hong Kong from 20 August to 22 December 2012. Among the total observed carbonyls, Formaldehyde (HCHO, 2.00 +/- 1.04 ppbv) presents the most abundant concentration and plays the most important role in OH removal with LoH value of 0.47 s( -1). To further dissect the secondary formation mechanism of HCHO at Hok Tsui, detailed modeling analyses were conducted by the OBM-AOCP model for two cases with different meteorological conditions. The result shows that HCHO production was dominated by the reactions of CH3O + O-2, and RO + O-2 (first-generation precursor of RO was Alkenes). The HCHO destruction pathways during two cases were governed by the reactions with OH and photolysis. The net generation rate of HCHO was controlled by meteorological conditions with alkenes (mainly ethylene (C2H4) and propylene (C3H6)) being the dominant parent hydrocarbons of HCHO. Overall, this study provides some new insights into the formation mechanisms of HCHO, especially their parent hydrocarbon species, underlines the important role of carbonyls in ozone pollution in Hok Tsui. Reducing the emissions of alkenes would be an effective way to mitigate photochemical pollution in the background atmosphere of China.