| The method based on a combination of sampling by Tenax absorbent turb and pretreating by thermal desorption in series, using gas-chromatography coupled with mass-spectrometry for subsequent determination has been developed for the analysis of volatile olefins. Field observations were conducted in both urban and suburban areas of Guangzhou to discuss the composition and content as well as chemical activity of olefins in the studed area. The spatial and temporal variations of olefins under an influence by the typical sea breeze were also analyzed, the results showed that:(1) 15 volatile alkenes were detected in the atmosphere of Guangzhou with their total concentration ranged from 2.37ppb to 17.65ppb. Among them, Isoprene, cis-2-butene, trans-2-butene,2-methyl-propylene and octene had a relative high level.(2) The composition and content of atmospheric alkenes in Guangzhou both showed significant temporal and spatial distribution. It was found that the mean concentrations of detected alkenes were higher in summer than in autumn, and suburban area than urban area. Anthropogenic emissions were the main sources of atmospheric olefins in urban area. However, since the contribution of biomass burning and natrual sources in the suburban area were significant, the concentrations of alkenes were slightly higher in suburban area then in urban area.(3) Alkenes were the largest contributor of volatile organic chemical reactivity in Guangzhou, and the chemical reactiveity of alkenes also showed significant spatial and temporal distribution, with their overall levels hihger in summer and suburban area than in autumn and urban area.(4) The photochemical smog was severely in Guangzhou in autumn. During this period, the most important contributors of ozone formation among all detected alkenes were isoprene, pentene, octene, propylene and butylene, accounting for 87.8% of the total ozone forming potential. While in the suburban area, isoprene, butene,2-pentene,1-pentene and octene with their OFP accounting for 85.3% of all the detectable alkenes were the dominant contributor to the ozone formation. In this region, the background values of atmospheric chemical activity from natrual source were hihger, ranged from 32.4%t o 39.5%. Butene, pentene and octene which were thought to been came from human activities should consider as priority pollutants.(5) The diurnal variation of alkenes in both urban and suburban area were different in sea-land breeze period from normal period. The concentrations of alkenes showed a higher level in sea-land breeze period than the normal period in the two studied area. It showed that, in the urban area, the concentration of alkenes was increasing during the sea breezn period, while in the suburban area, it showed a lowest level in this period untile middle of the night, and then rising in the period in which the sea breeze turn into land breeze.(6) During the sea-land breeze period, the chemical activity of atmosphere in urban showed an order of sea breeze period> transitional period of land breeze to sea breeze> transitional period of sea breeze to land breeze>land breeze period, and in the hole period, the chemical activity of atmosphere was mainly influented by isoprene,2-methyl-1,4-pentadiene. In the suburban area, the chemical activity of atmosphere showed an order of transitional period of sea breeze to land breeze> land breeze period> transitional period of land breeze to sea breeze> sea breeze period, and the key species which impacted on atmospheric chemcial activity in this region were isoprene,2-methyl-propylene and octene.
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