【摘要】 采集了宁波市区2003和2013年两期共1 130个土壤样品,测定了8种典型重金属元素的含量,运用污染指数评价法对土壤重金属污染程度进行了评价,运用地统计学方法剖析了污染的时空变异特征,并分别运用主成分分析和UNMIX受体模型解析了重金属的污染来源.结果表明:(1)除了As,两期重金属元素的含量均值都超过了浙江省土壤背景值和国家土壤背景值,说明土壤普遍存在重金属污染;从2003～2013年,所有元素的含量均值都不同程度地增大,说明10年间重金属污染普遍加剧;(2)单因子污染指数的评价结果表明,Hg为重度污染,Cd、Cu、Pb为中度污染,Zn、Cr、Ni为轻度污染,As为非污染状态;所有采样点的内梅罗综合污染指数都超过了警戒值,10年间综合污染指数> 3、呈重度污染的样本显著增加.(3)同种元素不同时期的污染空间格局相近,不同元素则呈现一定差异,Pb和Hg,Cr、As、Cu、Zn和Ni的空间分布特征具有相似性,高值区主要集中在污染企业分布密集和人类活动频繁的海曙、江北、江东、镇海四区;(4)研究区重金属污染源主要包括两类,即以Ni、As、Cr、Zn、Cd为主要成分的工业污染源,以Pb和Hg为主要成分的生活污染源,前者源自工业废水、废气和废渣的排放;后者源自于生活垃圾、汽车尾气及道路磨损造成的颗粒物和粉尘污染.更多还原

【Abstract】 In the present study,a total of 1 130 soil samples were collected in 2003 and 2013 in the Ningbo city district,and the content of eight typical heavy metals were measured. The degree of heavy metal pollution in the soil in the study area was evaluated using the pollution index evaluation method. The temporal and spatial variation in the pollution were analyzed by the geostatistics method,and principal component analysis( PCA) and the UNMIX model were used to analyze the heavy metal pollution sources. The results showed that:(1) excluding As,the mean values of the other seven heavy metals in both periods exceeded the soil background values in Zhejiang province and national background values,which indicated that heavy metal pollution is common in the soil from the study area. From 2003 to 2013,the mean content of all elements increased to some degree,indicating that the heavy metals pollution was generally aggravated in 10 a; the increase in the mean Hg content was the greatest.(2) The evaluation results based on the singlefactor pollution index showed that the pollution degree was high for Hg; moderate for Cd,Cu,and Pb; slight for Zn,Cr,and Ni; and unpolluted for As. The evaluation results based on Nemero’s comprehensive pollution index showed that the pollution index for all samples exceeded the precaution value, and the number of soil samples that were characterized as heavily polluted with a comprehensive pollution index over 3 had increased significantly.(3) The spatial distribution of the same heavy metal in different periods presented similar characteristics. Generally speaking,the spatial distribution of Pb was similar to that of Hg,and the spatial distributions of Cr,As,Cu,Zn,and Ni were similar to each other; high value areas were mainly concentrated in the four areas of Haishu,Jiangbei,Jiangdong,and Zhenhai districts,where the polluted enterprises were densely distributed and human activities were frequent.(4) Based on PCA and the UNMIX receptor model,the source analysis results of soil heavy metals in 2013 were essentially the same,i. e.,the source of heavy metal pollution in the study area included industrial sources and living sources. Industrial sources of heavy metal pollution had the highest contribution rate and derived from industrial wastewater,waste gas,and waste residue discharged by plasticizing,mining,and metallurgical enterprises; chemical and mechanical manufacturing enterprises; etc.,causing the accumulation of Cr,As,Cu,Zn,and Ni in the soil. The living sources had the second highest contribution rate and originated from the pollution of particulates and dust caused by domestic waste,automobile exhaust,and road wear. Additionally,natural factors had small contribution rates,mainly due to the spread of pollutants by prevailing winds and atmospheric settlement.更多还原