上海地区大气中二噁类分布特征的初步研究

为了研究上海地区大气中二噁英（PCDD/Fs）的污染水平、分布特征和相分配规律,分别选取了上海典型的工业区、居民区和郊区的采样点进行了大气样品的采集。通过对3个采样点的研究发现,上海地区的大气中二噁英的平均毒性当量浓度为0.201 pg/m^3,居民区最高,工业区其次,郊区最低。大气中二噁英排放的平均浓度属于典型的城市工业区水平。在常温下,大气中90%二噁英主要分布在颗粒物相中,从单体看,高氯代同系物主要分布在颗粒相中,而低氯代同系物则分布在气相当中。通过二噁英的气相/颗粒相分配系数Kp与蒸气压PL的关系式评价了污染物的气相/颗粒相分配行为。并应用Junge-Pankow模型预测了大气中的气相/颗粒相分配,通过与实测值的比较发现,上海地区大气中二噁英的气相/颗粒相分布十分接近于模型中的城市地区,郊区采样点和模型预测值最为吻合,工业区和居民区大气中的二噁英在颗粒物上的浓度则要高于模型预测值,对造成偏离的原因进行了分析,并对3个采样点周围的污染源进行了初步的探究。

Preliminary Study of PCDD/Fs in Ambient Air of Shanghai

In this study polychlorinated dibenzo-p-dioxinsand furans（PCDD/Fs） were monitored in the ambient air of Shanghai to evaluate their concentration, homologue profile, and gas-particle partition. Air samples were collected from three representative sampling sites of Shanghai： industrial area, residential area and suburb area. The average atmospheric PCDD/Fs concentration was comparable to the typical level of urban industrial sites. Our result showed that about 90% PCDD/Fs were partitioned into particulate phase. High-chlorinated PCDD/Fs dominated particle phase while low-chlorinated PCDD/Fs dominated gas phase. The plot of log gas/particle partitioning coefficient（Kp） versus log sub-cooled vapor pressure（PL） was used to describe the act of gas/particle partitioning in the ambient air of Shanghai.The Junge-Pankow model was used to predict the gas-particle partitioning of PCDD/Fs congeners. It was observed that the Junge-Pankow model slightly underestimated the particulate fraction of PCDD/Fs in the ambient air of residential area and industrial area, but coincided with the result of suburb area. The deviation and difference were analyzed and the possible pollution sources of the three sampling sites were preliminarily explored.