北江流域5种林分类型土壤重金属含量变异性研究

Variability of Soil Heavy Metal Content of Five Stand Types in Beijiang River Basin

探究北江流域不同林分类型的土壤重金属含量特征和重金属污染情况,为北江流域林地土壤重金属污染评价提供理论依据。以北江流域5种林分类型[桉树(Eucalyptus robusta)、竹(Bambusoideae)、杉木(Cunninghamia lanceolata)、马尾松(Pinus massoniana)和湿地松(Pinus elliotti)]的土壤为研究对象,分析0~40 cm土层土壤中铬(Cr)、镍(Ni)、铜(Cu)、锌(Zn)、铅(Pb)、汞(Hg)元素含量,同时采用单因子指数法、内梅罗综合指数法、地累积指数法和潜在生态风险指数法,评价各林分类型土壤重金属污染及其潜在生态风险。结果表明:(1)各林分土壤重金属含量均以Zn最高、Hg最低。(2)土壤重金属Cr、Ni、Cu、Zn元素两两之间存在极显著相关性,此外土壤重金属含量还受土壤pH、全氮(TN)、全磷(TP)、有机碳(OC)的影响,其中以TP影响最为显著。(3)5种林分土壤重金属污染评价结果大多表现为清洁或安全状态,仅地累积指数评价结果中,竹林土壤中Hg元素为轻度至中等污染;Hg元素的潜在生态风险水平为中等,其余重金属元素为轻微生态风险。本研究发现,北江流域林地土壤环境质量较好,大部分地区土壤重金属污染评价结果为清洁或无污染,可为北江流域林地土壤污染防控和区域生态保护提供基础数据和理论支持。

To examine the characteristics of soil heavy metal content and the pollution condition of different forest types in the Beijiang River Basin and to provide a theoretical framework for the assessment of heavy metal pollution,soil concentrations of Cr,Ni,Cu,Zn,Pb and Hg were investigated in the 0-40 cm soil layer of five different forest types(Eucalyptus robusta,Bambusoideae,Cunninghamia lanceolata,Pinus massoniana and Pinus elliotti)in the Beijiang River Basin.The single factor index method,Nemerow comprehensive pollution index method,geo-accumulation index method and potential ecological risk index method were used to evaluate the pollution and possible ecological risk of soil heavy metal contamination in each stand type.The results showed that:(1)Zn and Hg had the highest and lowest concentrations of heavy metals respectively in the soil of all stands.(2)The four heavy metal components of soil(Cr,Ni,Cu and Zn)had a strong link with one another.Additionally,soil pH,TN,TP and OC all had an impact on soil’s heavy metal content,with TP had the biggest impact.(3)Only the geo-accumulation index evaluation results revealed that the Hg element in the soil of the Bambusoideae stands was mildly to moderately contaminated.The soil of the five stands tested for heavy metal pollution was almost clean or safe.The potential ecological risk levels of mercury were moderate,while those of the other heavy metals were minimal.This study found that the soil environmental quality of the woodland in the Beijiang Basin was good,and the evaluation result of soil heavy metal pollution in the majority of areas was clean or no pollution,providing fundamental information and theoretical support for the prevention and control of soil pollution as well as for the regional ecological protection of the woodland in the Beijiang Basin.