湛江东北部农用地土壤重金属污染及生态风险评价

为探明湛江市东北部地区不同类型农用地土壤重金属污染及生态状况,保证土壤环境及农产品质量安全。本研究采集189个农用地表层土壤样品并分析了其中Cd、Hg、As、Pb、Cr、Cu、Ni、Zn等8种重金属元素含量,评估了重金属的富集程度、污染等级,预测其生态风险,并初步探讨了Cd、Hg的来源。结果表明:湛江市东北部地区农用地表层土壤Cd、Hg、As、Pb、Cr、Cu、Ni、Zn的平均含量分别为0.20、0.15、3.51、18.12、32.13、13.94、8.08、31.65 mg/kg,Cd和Hg存在明显的富集,均值分别为广东省土壤元素背景值的3.57和1.96倍,As、Pb、Cr、Cu、Ni、Zn平均值低于广东省背景值。13.23%的样品Cd元素含量高于《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB15618—2018)的风险筛选值,存在生态风险。区内农用地土壤样品未受污染的占93.12%,其中安全等级的样品占82.54%,轻污染和中污染分别占6.35%和0.53%。不同类型农用地的综合污染风险差异较大,旱地综合污染风险最低,果园最高,从低到高整体排序为:旱地、水浇地、乔木林地、水田、果园。整个研究区农用地土壤潜在生态风险等级以轻微和中等为主,共占样品总数的87.83%,有12.17%的样品风险等级为强或很强,元素Cd和Hg贡献较高。初步分析土壤Cd主要来源于化肥、农药、有机肥的过量施用,Hg主要来源于大气沉降。

Comprehensive ecological risk assessment for heavy metal pollutions in three phases in rivers

Literature lacked in providing a comprehensive research on heavy metal detection in aquatic, biological and sedimentary states of rivers. The present study was imparted with all these three components of the river. Heavy metal toxicity or pollution index was used as a tool for ecological risk assessment by considering the single state studies conducted by many researchers. An intensive ecological risk assessment model was constructed and heavy metals were indicated as a serious threat to the environment. The model was applied to determining five toxic heavy metals in three states of the Songhua River. According to the ecological risk index, heavy metal pollution in three phases was categorized as aquatic〉biological〉sedimentary, while the overall descending order of heavy metal ecological risk index was as Cd〉Hg〉As〉Pb〉Cr. Cd and Hg were selected as the priority pollutants of Songhua River.