长江三角洲典型地区工业企业的分布对土壤重金属污染的影响

EFFECT OF INDUSTRIAL DISTRIBUTION ON SOIL HEAVY METAL ACCUMULATION IN A TYPICAL AREA OF THE YANGTZE RIVER DELTA

以长江三角洲地区近年来经济发展较快的张家港市为例,在密集的大田采样和大田与企业周围采样结合的基础上,评价了该市土壤Cd、Hg、Pb污染状况;讨论了两种不同采样方式对土壤污染状况评价的影响;用土壤表层与底层重金属含量的比值(后简称元素比值)为指标讨论了不同类型企业对周围土壤重金属积累的影响。总的来看,张家港市土壤重金属整体平均值与环境背景值接近,明显低于国家环境质量(GB 15618-1995)二级标准和中国绿色食品生产基地环境土壤污染限值(NY/T391-2000)。但存在少数样点超标和超限现象,空间上有小面积高含量土壤分布,且主要局限于企业周围的小范围内。采样方式对土壤污染的评价有明显的影响,对Cd和Pb而言,大田采样方式下他们的含量要明显低于两种方式结合的情况下(p<0.05),而Hg元素则相反,当大田采样与企业周围采样相结合可使得土壤中Hg元素高含量的分布面积明显增大。绝大部分企业周围土壤样品的元素比值要明显高于大田采集的土壤。除冶金类企业有着明显的Pb单一聚集外,化工、电子类企业往往导致了多个元素的积累,企业对周围土壤存在复合污染的可能性。这些结果为该市或类似地区的环境质量调查和评价、环境治理提供了重要的基础资料和决策依据。

Situated at Yangtze Rive Delta（YRD）, Zhangjiagang City has been undergoing a very rapid economic development since the adoption of the reform and opening policy in the 1980s. Based on intensive soil sampling from large fields and fields near the factories, （ Ⅰ ） status of soil heavy metal （Cd, Hg, and Pb） pollution, （ Ⅱ） effect of sampling methods, i.e. sampling in large fields （A） and in combination of large fields and fields near factories （B） on the assessment of soil heavy metal pollution, and （Ⅲ ） effect of industrial types on soil heavy metal accumulation with the aid of ratios of soil heavy metal content in top-soil and sub-soil （element ratio） were discussed in the paper. In general, the soil heavy metal pollution in Zhangjiagang City were not serious with the average content of the elements close to their respective background value or lower than criteria of the second grade of the national standard for soil environmental quality （GB15618-1995） and the limitation values for soil environment pollution of green-food production bases （NY/T391-2000）. However, heavy metal contents in some samples were over the standard, resulting in a distribution of small area of soils with high element contents. The sampling methods had a significant effect on assessment of soil pollution. For Cd and Pb, the soils had a lower contents of the elements （p 〈 0.05） from method A than B. However, it is contrary for Hg. The area of soils with high element content was larger for three metals from methods B than A. Most of the samples from the soils near factories were higher in element ratio than those from large fields. Metallurgical industry caused a significant accumulation of Pb, whereas the chemical industry and electrical industry could cause accumulation of more metals. All these results provide valuable basic data and a decision-making basis for planning of investigation, assessment and management of soil environmental quality in Zhangjiagang City or other similar regions in China.