琼北火山岩地区水田和旱地土壤中重金属的累积特征比较

Comparison of heavy metal accumulation characteristics between dry land and paddy field of volcanic rock area,North of Hainan

为分析琼北火山岩地区土壤中重金属(As、Cd、Cr、Pb、Ni、Hg)的累积特征,采集旱地和水田的土壤表层样品,并对样品理化性质及重金属含量进行了分析,采用单因子污染指数法和内梅罗综合污染指数法对重金属污染状况进行了评价。结果表明,研究区旱地与水田土壤均呈强酸性-酸性,旱地土壤阳离子交换量(CEC)(4.66 cmol/kg)略大于水田土壤CEC(3.42 cmol/kg),表明旱地土壤保持养分的能力优于水田土壤。与海南土壤背景值比较,研究区旱地和水田土壤中Cd、Cr、Pb和Ni 4种重金属均有不同程度的累积,其中Cd累积程度较重。研究区旱地和水田土壤中Cr与Ni均具有较高的正相关关系,说明旱地和水田土壤中Cr与Ni可能同源,且受基性火山岩地质背景的影响较大。内梅罗综合污染指数评价结果表明,研究区旱地土壤重金属污染明显高于水田土壤,水田土壤重金属为轻度污染,而旱地土壤重金属已达到中度污染,尤其是Cr和Ni污染比较严重,应引起重视。

To analyze the accumulation characteristics of heavy metals(As,Cd,Cr,Pb,Ni,Hg)in the soil of the volcanic rock area in North of Hainan,surface soil samples were collected from dry land and paddy field,and the physicochemical properties and heavy metal content of the samples were analyzed.The single factor pollution index method and the Nemerow comprehensive index method were used to evaluate the heavy metal pollution status.The results showed that both dry land and paddy field soil in the study area were strongly acidic to acidic,and the cation exchange capacity(CEC)of dry land soil(4.66 cmol/kg)was slightly higher than that of paddy field soil(3.42 cmol/kg),indicating that the nutrient retention ability of dry land soil was better than that of paddy field soil.Compared with the background values of soil in Hainan Province,the study area showed varying degrees of accumulation of four heavy metals,namely Cd,Cr,Pb and Ni,in both dry land and paddy field soil,with Cd being the most heavily accumulated.There was a high positive correlation between Cr and Ni in the soil of dry land and paddy field in the study area,indicating that Cr and Ni might be homologous and greatly influenced by the geological background of basic volcanic rock.The evaluation results of the Nemerow comprehensive pollution index indicated that the heavy metal pollution in the study area’s dry land soil was significantly higher than that in paddy field soil.The heavy metal pollution in paddy field soil was mild,while the heavy metal pollution in dry land soil had reached moderate pollution,especially the pollution of Cr and Ni,which should be given sufficient attention.