基于碳同位素组成的大气NMHCs光化学寿命研究

利用热解析-气相色谱-同位素质谱联用仪测定了兰州市冬季和夏季昼夜大气非甲烷烃(NMHCs)的稳定碳同位素组成.结果表明,兰州市冬季大气NMHCs的δ13C值为-30.5‰～-24.3‰,夏季为-31.9‰～-24.2%,受燃煤烟气排放的影响,冬季大气NMHCs的δ13C值明显大于夏季;冬季大气NMHCs的δ13C值夜晚大于白天,夏季不同时间点C4、C5化合物的同位素值相差不大,正己烷和正庚烷的δ13C值白天比夜晚要高.利用"碳氢化合物同位素时钟"计算出正己烷和1-丁烯在兰州市夏季大气中的平均光化学寿命分别约为6d和25min.

Photochemical age of atmospheric nonmethane hydrocarbons based on stable carbon isotopic composition

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.