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菏泽市冬季PM2.5中二元羧酸类SOA的昼夜变化特征
摘要点击 158  全文点击 62  投稿时间:2018-04-05  修订日期:2018-04-30
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中文关键词  二元羧酸  昼夜变化特征  液相形成机制  PM2.5  菏泽市
英文关键词  dicarboxylic acids  diurnal variations  aqueous formation mechanism  PM2.5  Heze City
作者单位E-mail
孟静静 聊城大学环境与规划学院, 聊城 252000
中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室, 西安 710061 
mengjingjing@lcu.edu.cn 
刘晓迪 聊城大学环境与规划学院, 聊城 252000  
侯战方 聊城大学环境与规划学院, 聊城 252000
中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室, 西安 710061 
 
李静 聊城大学环境与规划学院, 聊城 252000  
魏本杰 聊城大学环境与规划学院, 聊城 252000  
邢继钊 聊城大学环境与规划学院, 聊城 252000  
中文摘要
      为研究菏泽市冬季大气气溶胶中二元羧酸类化合物的昼夜变化特征与形成机制,于2017年冬季(12月)进行为期1个月的PM2.5样品采集,并分析二元羧酸、酮羧酸、α-二羰基化合物及左旋葡聚糖等化学组分.结果表明,菏泽市冬季PM2.5中白天二元羧酸与酮羧酸的总浓度均呈昼高夜低的变化特征,但α-二羰基化合物(二元羧酸的重要前体物)的变化特征却与之相反,表明白天气溶胶的氧化程度比夜晚强.论在白天还是晚上,草酸(C2)均是浓度最高的二元羧酸,其次是邻苯二甲酸(Ph)、丁二酸(C4)和丙二酸(C3),与其他城市地区的分子组成是相似的.由C3/C4的比值与温度(T)间的相关性分析可知,菏泽市冬季有机化合物主要受本地源的影响,而受远源输入的影响很小.C2与SO42-、气溶胶实际酸度(pHIS)的相关性分析表明,C2主要是在液相中经酸催化的二次氧化反应形成的.因为主要的二元羧酸类化合物(C2、Gly和mGly)与左旋葡聚糖(Levo)的相关性很强,且K+/OC的平均比值为0.06(范围为0.03~0.13),所以可以得出二元羧酸类化合物及K+主要受生物质燃烧的影响.
英文摘要
      To identify the diurnal variation and formation mechanism of dicarboxylic acids and related compounds in PM2.5 from Heze City, PM2.5 samples were collected in the winter (December) of 2017, which were subsequently analyzed for dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, and levoglucosan (Levo). The results showed that the total concentrations of dicarboxylic and ketocarboxylic acids were higher during daytime than those during nighttime. In contrast to the diurnal variation of dicarboxylic and ketocarboxylic acids, the total concentrations of α-dicarbonyls exhibited higher concentrations in nighttime than in daytime. Because α-dicarbonyls are the major precursors of dicarboxylic acids, the opposing patterns suggest that the photochemical oxidation in daytime is stronger than that in nighttime. Oxalic acid (C2) is the dominant species during both day-and nighttime, followed by phahalic acid (Ph), succinic acid (C4), and malonic acid (C3), which is consistent with that in other urban regions. The mass ratios of C3/C4 (R2>0.7) correlated strongly with temperature, indicating that organic compounds in the atmosphere of Heze City are mainly derived from the photochemical oxidation of local emissions rather than long-range transport in winter. C2 correlated with in-situ pH and SO42-, suggesting that aqueous-phase oxidation was the major formation pathway of C2, which is driven by acid-catalyzed oxidation. Since the major SOA (C2, glyoxal, and methyglyoxal, secondary organic aerosol) correlated with Levo and the average mass rations of K+/organic carbon was 0.06 (ranging from 0.03 to 0.13), it can be concluded that the dicarboxylic acids and related SOA and K+ in Heze City were significantly influenced by biomass burning in winter.

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