浙北某县域耕地土壤重金属空间分异特征、污染评价及来源分析

以浙江省北部某产粮县的267个耕地土壤样本的5种土壤重金属As、Hg、Cr、Cd、Pb为研究对象,综合运用结合GIS手段、单因素、内梅罗综合评价法以及改进模糊综合评价法,分析研究区土壤重金属污染的空间分异、污染评价以及来源分析。结果表明:As、Hg、Cr、Cd、Pb平均含量分别为8.17、0.211、67.03、0.224、37.26 mg·kg-1,均符合国家相应的土壤环境质量二级标准。土壤重金属半方差函数拟合块基比大小顺序为HgPbCdAsCr,其中Pb、Cd、As、Cr处于中等程度相关,Hg则表现出了较弱的空间相关性,受人类活动影响较大。该县土壤整体清洁,仅少数样点出现污染情况。这部分污染主要分布在县城周边,以Hg-Cd复合污染的形式存在,主要来源于工矿企业长期燃煤导致的粉尘挥发以及当地蓄电池产业发展所带来的负面影响。

Spatial differentiation characteristics, pollution evaluation, and source analysis of heavy metals in farmland soil in a county in northern Zhejiang Province, China

The evaluation of heavy metal pollution and spatial pattern characteristics on cultivated land is of great significance for regional farmland protection and agricultural product safety. Five kinds of soil heavy metals, As, Hg, Cr, Cd, and Pb, from 267 soil samples in a grain producing county of northern Zhejiang Province were analyzed. GIS technology, the single factor and Nemero indexes, and an improved fuzzy comprehensive evaluation method were used to analyze the spatial differentiation, pollution assessment, and source analysis of heavy metal pollution in the study area. The results showed that the average contents of As, Hg, Cr, Cd, and Pb were 8.17, 0.211, 67.03, 0.224, and 37.26 mg·kg^-1, respectively, which were all in line with the secondary grade standard of national soil environmental quality. The soil heavy metal block ratio of semivariance function fitting results showed that Hg > Pb > Cd > As > Cr, where Pb, Cd, As, and Cr were moderately related. At the same time, Hg showed a weaker spatial correlation, which is greatly influenced by human activities; the soil in this county was pretty clean and only a few samples were polluted. Pollution mainly occurred in the surrounding areas of the county town, and existed in the form of HgCd multiple contamination. This pollution was mainly due to dust settlement caused by long-term coal combustion in local industrial and mining enterprises, as well as the development of the local battery industry.