城市雨水和土壤中持久性有机污染物分析

Analysis of the persevering organic pollutants in the rainwater and their effect on the urban soil protection

为分析城市环境中持久性有机污染物状况,以西安市城区为研究对象,按照城市布局设置10个代表性采样点,分别采集初期雨水和地表土壤样品,采用气相色谱法(GC)测定样品中有机氯农药和多氯联苯两大类持久性有机污染物的含量。结果表明:西安城区雨水、土壤中均含有持久性有机污染物,雨水中以pp’-DDT、α-六六六、pp’-DDD、PCB169、PCB189、PCB126居多,土壤中以op’-DDT、α-六六六、pp’-DDT、PCB169、PCB189、PCB77居多;无论雨水还是土壤中,都是有机氯农药含量高于多氯联苯含量;雨水中pp’-DDT、多氯联苯PCB169平均质量浓度分别超过GB 3838—2002《地表水环境质量标准》限值的12倍、100倍,土壤中的六六六和DDT质量比尚未超过GB15618—1995《土壤环境质量标准》一级标准。有机氯农药和多氯联苯的逸度商(fs/fa)均远小于1,西安城区POPs的迁移总趋势是由雨水向土壤表层聚集,降雨会将大气中的POPs通过淋洗等作用带到土壤表层,大气为污染物的源,土壤为其最终的汇集地。

This article is inclined to introduce its analysis of the long-lasting effect of the organic pollutants（ POPs） in the rainwater on the urban soil protection. In order to find the distribution status-quo of the POPs in the urban environment of Xi＇an City,we have collected the samples of initial rainwater and the soil within10 cm to the ground surface from the 10 representative sampling spots in all the suburban areas of Xi＇an City. What we have done to the contents of the organo-chlorine pesticides（ OCPs） and the polychlorinated biphenyls（ PCBs） in the samples has been evaluated and identified by the gas chromatography（ GC）. The results of our study show that all the samples are qualified to represent the remaining organic pollutants in the urban rainwaters and the typical soils from Xi＇an City. The aforementioned pollutants in the rainwater have been found mainly consisting of pp ＇-DDT,α-HCH,pp＇-DDD,PCB169,PCB189 and PCB126,whereas the pollutants in the soil have been found mainly made of op＇-DDT,α-HCH,pp＇-DDT,PCB169,PCB189 and PCB77. However,as a conclusive idea,in spite of a great difference in what may exist in the rainwater or the soil,it can be said that the organochlorine content proves to be higher than that of the polychlorinated biphenyls（ PCBs）. What is more,the average concentration of pp＇-DDT and PCB169 in it has been discovered over 12 times and 100 times,respectively,as compared to the national standard for the Surface Water Environment Quality（ GB 3838—2002）.Nevertheless,the average concentration of HCH and DDT in the soil has been detected below the primary standard based on the National Standard of Soil Environment Quality（ GB 15618—1995）. The results of fugacity quotient（ fs/ fa） reveal that the fs/facontent of organochlorine pesticides and polychlorinated biphenyls has been shown far less than 1,signifying that the general migration trend of POPs in the suburban areas of the city is from the rainwater to the surface soil,with the rainwater taking away the atmospheric POPs to the surface soil through leaching and public cleaning,which implies that the pollutants from the atmosphere and the soil turn to be the ultimate gathering container.