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研究报告

Seasonal variation and source analysis of carboxylic acids in PM_2.5 in the urban area of Chongqing

基金项目：国家自然科学基金（No.41403089，41205095）；中国科学院重点部署项目（No.KJZD-EW-TZ-G06-04）；国家环境保护大气复合污染来源与控制重点实验室开放基金（No.SCAPC201310）

摘要：本文针对重庆主城区4个采样点PM_2.5中羧酸开展研究，通过GC-MS分析，定量分析了16种饱和脂肪酸、21种不饱和脂肪酸和8种二元羧酸等多种物质的浓度水平，进而对羧酸的季节变化及来源进行了探讨。羧酸日均总浓度为130.42~1953.79 ng·m^-3，一元脂肪酸和二元羧酸在各采样点浓度差异显著。一元脂肪酸呈明显的季节变化，夏季最高（961.97 ng·m^-3），冬季最低（49.24 ng·m^-3）。饱和脂肪酸中偶数碳优势明显，以C₁₆（棕榈酸）和C₁₈（硬脂酸）最为丰富。二元羧酸也呈明显的季节变化，在冬季最高（432.04 ng·m^-3），春季最低（64.57 ng·m^-3）。二元羧酸以丙二酸、丁二酸和戊二酸为主。细菌活动和烹饪油烟对一元脂肪酸具有较大的贡献，光化学氧化作用则对二元羧酸贡献较大。

Abstract：This study reported the seasonal and spatial distribution of carboxylic acids in PM_2.5 at four sampling sites in the urban area of Chongqing. The concentrations of 16 saturated fatty acids, 21 unsaturated fatty acids and 8 dicarboxylic acids were determined using Gas Chromatography-Mass Spectrometry (GC-MS). The seasonal variations and the sources of these species were also discussed. The results showed that the average daily concentration of total carboxylic acids was 130.42~1953.79 ng·m^-3. The concentration of fatty acids and dicarboxylic acids at each sampling site were significantly different. Unique seasonal variations of fatty acids were observed and their concentrations were high in summer (961.97 ng·m^-3) and low in winter (49.24 ng·m^-3). Saturated fatty acids showed the significance of the even carbon number acids to the odd carbon number acids with the most abundance of C₁₆ (palmitic acid) and C₁₈ (stearic acid). Dicarboxylic acids also showed strong seasonal variations. However, the dicarboxylic acids showed the highest concentration in winter (432.04 ng·m^-3) and the lowest in spring (64.57 ng·m^-3). Malonic acid, succinic acid and glutaric acid were predominant in dicarboxylic acids. The study suggested that bacterial activities and cooking oil fume were the major contributors to fatty acids and dicarboxylic acids were influenced by photochemical activities.