北京及周边城市一元脂肪酸大气颗粒物干沉降通量及来源分析研究

城市大气颗粒物中有机质浓度不断攀升,其中有机酸为重要成分之一.通过PUF膜收集大气颗粒物干沉降,采取溶剂提取、衍生化和GC-MS分析,对2007年12月～2008年11月间,北京及其周边城市天津、唐山、保定的大气颗粒物干沉降中一元脂肪酸含量进行了观测研究.结果表明,干沉降中可检出所有C10～C24的烷酸,以及油酸、亚油酸和桐油酸3种烯酸.干沉降量最大的是正十六烷酸,其次为正十八烷酸,油酸、亚油酸的含量也相对较高.年均干沉降量最大的城市为北京,其次是保定、唐山、天津,沉降量分别为0.32、0.25、0.16和0.12 kg.(hm2.a)-1.北京一元脂肪酸的平均日沉降量最大值出现在8～9月,达262.43μg.(m2.d)-1;4～5月次高,为130.98μg.(m2.d)-1;天津市最高值出现在4～5月,为66.04μg.(m2.d)-1;唐山出现在2～3月,为73.62μg.(m2.d)-1;保定出现在4～5月,为173.28μg.(m2.d)-1.源解析显示,京津冀四城市的一元脂肪酸的年度干沉降以机动车排放源最为重要,其次为微生物源和餐饮源,秋季北京大气餐饮源排放脂肪酸量很高.

Atmospheric Dry Deposition Flux and Sources of Monocarboxylic Acids in Beijing and Surrounding Cities

The concentration of organic matter has been increased in the urban atmospheric particles,in which the organic acids are one kind of the important species.Dry deposition of 17 n-alkanoic acids(C10-C24) and 3 alkenoic acids(including oleic,linoleic and eleostearic acid) were determined by GC/MS from Dec.2007 to Nov.2008 in Beijing,Tianjin,Tangshan and Baoding.The results showed that C16 and C18 were both the most abundant species and oleic acid and linoleic acid were in the next place.The annual dry deposition flux of monocarboxylic acids was the highest in Beijing 0.32 kg·(hm2·a)-1,followed by Baoding,Tangshan and Tianjin,which were 0.25,0.16,0.12 kg·(hm2·a)-1,respectively.The maximum deposition flux of monocarboxylic acids in Beijing was found in August to September 262.43 μg·(m2·d)-1].In Tianjin,the maximum deposition flux was found in April to May 66.04 μg·(m2·d)-1].For Tangshan and Baoding,the fluxes were found in February to March 73.62 μg·(m2·d)-1] and in April to May 173.28 μg·(m2·d)-1],respectively.Source distribution implied that vehicle exhaust was the most important source.The contribution of microbial decomposition litter and cooking emission were large as well while cooking emission contributed more to monocarboxylic acids in autumn of Beijing.