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.