中文摘要：

为了解西安城区大气中多氯联苯（Polychlorinated biphenyls,PCBs）的浓度水平、季节变化特征及来源,于2012年夏季、冬季分别对西安市城区大气进行每周1次的主动采样,共获得22对大气样品（气态和颗粒态）.结果表明,西安城区大气中∑64PCBs的浓度为76.21~338.77pg·m-3,平均浓度为183.85 pg·m-3,且主要存在于气态样品中.组成上主要以低氯代PCBs为主,其中,三氯和四氯代PCBs占总浓度的59.64%~91.39%.气态样品中,夏季、冬季PCBs的平均浓度分别为201.68、151.11 pg·m-3;颗粒态样品中,冬季PCBs平均浓度是夏季的6.65倍.通过主成分分析法对西安城区大气中PCBs的来源进行解析,发现主成分1的方差贡献率为36.06%,主要为来自我国生产的变压器油源;主成分2的方差贡献率为20.29%,可能来自于油漆的使用.

英文摘要：

To understand the concentrations,seasonal variation,and sources of polychlorinated biphenyls（ PCBs） in the ambient air of Xi’ an City,China,twenty-two air samples（ in both gaseous and particulate phases） were collected for 24 hours per week using an active air sampler during summer and winter in 2012 in Xi’an City. The results showed that the concentrations of ∑64PCBs ranged form 76. 21 to 338. 77 pg·m-3with a mean of 183. 85pg·m-3,with much higher concentration for PCBs in gas-phase than that in particle-phase. Lower molecular weight PCB congeners were dominated,and the ratio of concentrations for tri- and tetra-CBs to the total PCBs concentrations ranged from 59. 64% to 91. 39%. For the gaseous phase,the average concentration of PCBs was 201. 68 pg·m-3in summer,higher than 151. 11 pg·m-3in winter. However,for the particular phase,the mean concentration in winter was 6. 65 times higher than that in summer. Principal component analysis（ PCA） was applied to identify the sources of PCBs in the air of Xi’an City. The first principal component（ PC1）,accounting for 36. 06% of the total variance,was recognized as transformer oil produced in China. PC2 accounted for 20. 29%,which might be originated from the use of painting.