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| Photochemical age of atmospheric nonmethane hydrocarbons based on stable carbon isotopic composition |
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Abstract The diurnal stable carbon isotopic composition of nonmethane hydrocarbons (NMHCs) in winter and summer in Lanzhou was detected by thermal desorption-gas chromatography-isotope ratio mass chromatography (TD-GC-IR-MS) system. δ13C values of NMHCs were -30.5‰~-24.3‰ in winter, which was influenced by coal-combustion exhaust and higher than that in summer (-31.3‰~-24.2%). The δ13C values were generally higher at night than that in the daytime in winter, while the δ13C values of C4 and C5 NMHC compounds were similar in the different sampling time except higher δ13C values of n-hexane and n-heptane in the daytime in summer. Based on the hydrocarbon isotopic clock, the average photochemical ages of n-hexane and 1-butene in summer were 6d and 25min, respectively.
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Received: 13 January 2010
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