| Polychlorinated biphenyls(PCBs) are hard to degradation in the environmental media, studies showed that PCBs exhibiting carcinogenicity, reproductive, immunity toxicity, nervous system in living creatures and humans, and accumulated in the body so made threaten for the health of humans. PCBs had been banned to produce and use in the global region at 70 s twenty century, one kind of the first bound POPs in the Stockholm Convention, also are one of global topics. The studies about PCBs mainly concentrated on the Pearl River Delta region and e-waste region in China, to evaluate the concentrations, compounds, seasonal variation, however, the studies focused on source identification and gas/particle partitioning are rare. In order to grasp the concentrations of PCBs, the consistent characterizes, seasonal variation and gas/particle partitioning behavior systematically, and try to understand the sources, both gaseous and particulate phases samples were collected concurrently using an active air sampler lasting one year time in Xi’an City.Eighty-four congeners were quantified by GC-MS, and sixty-four congeners were above the detection limit. ∑63PCBs concentration(in both gaseous and particulate phases) of PCBs ranged form 58.38 to 449.38 pg/m3, with mean concentration 226.60±99.08pg/m3. The total gas phase ranged form 56.42~447.49 pg/m3, the mean ratio of gas phase to the total PCBs was 95.53±4.30%, while the particle phase ranged from 2.03~55.30pg/m3. The compositions of PCB homologue dominated by tri- and tetra-PCBs, to the total PCBs concentrations which ranged from 21.6%~77.39%, 37.04±9.93%, respectively. However hexa- and above PCBs just took account ranged from 0.75%. while the particle bound only contributed 4.47±4.30%. The concentrations of PCBs has obvious seasonal variation in ambient air in Xi’an City, total concentrations ranged spring>autumn>summer>winter.The result from study of gas-particle partitioning in ambient air in Xi’an City indicated that slopes obtained from linear regression between logKP verse logPo L(logKOA and logKP)were shallower than the theoretical value of-1(1) at equilibrium condition, indicated that partitioning of PCBs between the gas and particle phases in the atmosphere in Xi’an City was under non-equilibrium conditions. And we use Junge- Pankow adsorption model and Harner-Bidleman absorption model to estimate gas-particle partitioning of PCBs, both models predicted values tended to overestimate the φ values and KP values compared to those obtained from field measurements. In addition, the predicted values form absorption models agree relatively better with those observed ones for low molecular weight(LMW) PCBs than adsorption models, while almost the same for high molecular weight(HMW) PCBs in both models.We try to identify the sources of PCBs in ambient air in Xi’an City, the relatively shallower slope(-1698.61) obtained from Clausius-Clapeyron equation indicated that the gas phase PCBs in the air in Xi’an City was more obviously influenced by the transformation than evaporation at sampling sites. Principal component analysis(PCA) was applied to identify the sources of PCBs in the air of Xi’an City, principal comonent1(PC1) accounted for 29.95% of the total variance, and was recognized as transformer oil produced in China. PC2 accounted for 13.07%, which might be originated from the transformation. The interpretation consisted with the fact that there were many historical PCBs sites in Xi’an City. |
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