浙西球川富硒耕地土壤地球化学特征及地下水影响因素

Soil Geochemical Characteristics and Groundwater Influencing Factors of Selenium-enriched Arable Land in Qiuchuan Western Zhejiang

为系统研究球川富硒区耕地土壤地球化学特征及地下水影响因素,采集了研究区耕地232件表层土壤样和37件地下水样,分析了As、Hg、Cr、Cu、Zn、Ni、Cd、Pb8种重金属和Se等元素含量。通过测试结果统计分析探究了该区富硒土壤地球化学特征。结果表明:区内表层土壤硒含量主要集中于0.2~0.75 mg/kg,平均含量0.41 mg/kg,高于浙江省平均值,且硒含量高值区与荷塘组地层走向分布基本一致;富硒区土壤存在一定重金属污染风险,污染风险主要来自Cd,其次为Cu、As、Ni,Cd点位超标率达7.76%,超标点位分布总体与荷塘组黑色岩系分布位置一致;污染综合评价以清洁为主,占比86.64%,轻度以上污染样品数占总样品数2.57%,总体土壤重金属污染不严重;潜水样检测结果反映该区地下水并未受到污染,pH、Se、Cd、As、Pb、Cu、Zn及Cr6+各项地下水指标均低于《地下水质量标准》(GB/T 1448—2017)IV类限值标准,地下水质量综合评价为IV类。潜水Se、Cd含量与对应土壤Se、Cd含量都不相关,反映Se和重金属元素在土壤中纵向迁移表现不明显。

In order to systematically study the soil geochemical characteristics of cultivated land in Qiuchuan Se-enriched area and the influencing factors of groundwater,232 surface soil samples and 37 groundwater samples were collected from cultivated land in the study area.The element content of As,Hg,Cr,Cu,Zn,Ni,Cd,Pb and Se was analyzed.Through the statistical analysis of the test results,the geochemical characteristics of the Se-enriched soil in this area were explored.The results show that the surface soil selenium content in the area is mainly concentrated in the range of 0.2-0.75 mg/kg,with an average content of 0.41 mg/kg,which is higher than the average value of Zhejiang Province,and the distribution of high-value areas of selenium content is basically consistent with the stratigraphic strike distribution of the Hetang Formation.There is a certain risk of heavy metal pollution in the soil in the Se-enriched area.The pollution risk mainly comes from Cd,followed by Cu,As,and Ni.The excess rate of Cd points is 7.76%.The distribution of over-standard points is generally consistent with the distribution of black rock series in the Hetang Formation.The comprehensive evaluation of pollution is mainly based on cleanliness,accounting for 86.64%,the number of samples with more than mild pollution accounts for 2.57%of the total number of samples,and the overall soil heavy metal pollution is not serious.The diving sample test results show that the groundwater in the area is not polluted.The groundwater indexes of pH,Se,Cd,As,Pb,Cu,Zn and Cr6+are all lower than the limit standard of Class IV in the Groundwater Quality Standard(GB/T 1448-2017),and the comprehensive evaluation of groundwater quality is Class IV.The contents of submerged Se and Cd were not correlated with the corresponding soil Se and Cd contents,reflecting that the longitudinal migration of Se and heavy metal elements in the soil was not obvious.