黔西南某农用地土壤重金属风险评估与来源解析

Risk Assessment and Source Analysis of Heavy Metals in Soil on a Farm Land in Southwest Guizhou Province

【目的】了解喀斯特地区小尺度区域农用地土壤重金属的含量特征和生态风险,为利用土地功能和保护耕地土壤环境提供参考。【方法】在黔西南中部某农用地土壤上共布设27个点位,采集表层土壤(0~20 cm)样品,分析测定pH与Cd、Hg、As、Pb、Cr、Cu、Zn和Ni等8种重金属元素,采用《土壤环境质量-农用地土壤污染风险管控标准》(GB 15618—2018)为评价标准,分析其分布特征、生态风险和来源。【结果】研究区土壤pH为5.46~8.07,重金属Zn、Cr、Pb、Ni、As、Cu、Cd与Hg平均含量分别为154.24、153.71、64.25、61.76、50.38、49.86、0.41和64.25 mg/kg。研究区农用地土壤受As和Cd污染指数分别为1.68和1.38。8种重金属的危害指数(I_(R))为69.00,小于生态危害下限(I_(R)=150)。Cd与Pb,Hg与As、Cu、Zn、Ni,As与Cu、Zn、Ni、Cr,Cr与Cu、Zn、Ni,Cu与Zn、Ni,Zn与Ni间分别具有同源性,存在复合污染。As、Hg、Cr、Cu、Zn、Ni在第一主成分有较高载荷,其方差贡献率为57.565%,含量较高原因主要为长期含重金属化肥施用造成;Cd和Pb在第二主成分中有较高载荷,其方差贡献率为80.277%,含量较高原因主要为成土母质中含量较高。【结论】研究区农用地土壤pH为5.46~8.07,已受不同程度As和Cd污染;Cr和Ni污染处于尚清洁范围;Hg、Pb、Cu和Zn处于清洁范围。污染程度为轻微生态危害。

【Objective】In order to understand the content characteristics and ecological risk of heavy metals in agricultural soils in small-scale areas of karst regions,the present paper provides reference for the utilization of land function and the protection of cultivated soil environment.【Method】A total of 27 sites were laid on soil on agricultural land in the southwestern of Guizhou Province,samples of surface soil(0-20)cm were collected,and 8 heavy metal elements such as pH and Cd,Hg,As,Pb,Cr,Cu,Zn and Ni were analyzed and determined.The‘Soil Environmental Quality-Soil Pollution Risk Control Standard for Agricultural Land’(GB15618-2018)was used as the evaluation criteria to analyze its distribution characteristics,ecological risks and sources.【Result】The results showed that the soil pH in the study area was 5.46 to 8.07,and the average contents of heavy metals Zn,Cr,Pb,Ni,As,Cu,Cd and Hg were 154.24,153.71,64.25,61.76,50.38,49.86,0.41 and 64.25 mg/kg,respectively.The soil pollution index of agricultural land in the study area was 1.68 and 1.38,respectively.The hazard index(I_(R))value of 8 kinds of heavy metals was 69.00,which was less than the limit of ecological hazard(I_(R)=150).Cd and Pb,Hg and As,Cu,Zn,Ni,As and Cu,Zn,Ni,Cr,Cr and Cu,Zn,Ni,Zn and Ni have homology respectively,and there is compound pollution.The results of the main component analysis show that As,Hg,Cr,Cu,Zn,Ni have a higher load in the first main component,the variance contribution rate is 57.565%,the content is mainly caused by the long-term application of heavy metal fertilizer;Cd and Pb have higher load in the second principal component,and their variance contribution rate is 80.277%.The higher content is mainly due to the higher content in the parent material.【Conclusion】The soil pH of agricultural land in the study area is 5.46-8.07,which has been polluted by As and Cd to different degrees.Cr and Ni pollution is still clean range;Hg,Pb,Cu and Zn are in the clean range.The pollution level is slight ecological hazard.