湘西不同植被类型土壤重金属分布及相关性研究

【目的】探讨湘西地区不同植被下土壤环境的状况,揭示土壤富集重金属元素的规律。【方法】以湖南湘西地区针叶林、针阔混交林、阔叶林和灌木林4种森林土壤不同层次(0~15 cm和15~30 cm)的Cd、Cu、Ni、Pb、Zn为研究对象,采用单因素分析法和主成分分析法分析重金属分布及相关性。【结果】不同植被下土壤中5种重金属含量的变异系数为0.18%~0.69%,由大到小的排列顺序为Cu>Zn>Ni>Pb>Cd。主成分分析表明Cu和Cd在PC1中有较大的荷载值,在PC2中有中等的荷载值。各因素相关性分析结果显示,灌木林土壤容重与Zn之间存在显著的负相关性,针叶林土壤容重与Cu之间存在显著的正相关性;灌木林土壤有机质与Cd之间有显著的正相关性,针叶林土壤pH值与Ni和Zn之间有显著的正相关性;针阔混交林土壤pH值与Pb、Cu和Ni之间存在显著的正相关性,灌木林土壤重金属含量之间的相关性较显著。【结论】湘西地区不同植被类型土壤重金属含量的垂直分布规律存在差异,表现为针阔混交林的上层土壤中重金属含量均低于下层土壤,常绿阔叶林的上层土壤中重金属含量均高于下层土壤,而针叶林和灌木林土壤中重金属含量无差异性变化;湘西地区土壤容重、有机质、坡度、pH值、土层厚度对Cd含量的影响较大,海拔对Pb、Ni和Cu的影响较大,坡度对Ni的影响较大;湘西地区灌木林中重金属来源相同的可能性相较于其他3种植被类型更大。

Study on distribution and correlation of heavy metals in soils of different vegetation types in Xiangxi autonomous prefecture

【Objective】The situation of soil environment under different vegetation in western Hunan was discussed and the law of heavy metal enrichment in soil was revealed.【Method】Cd,Cu,Ni,Pb,Zn in different layers(0-15 cm and 15-30 cm)of coniferous forest,mixed coniferous and broad-leaved forest,broad-leaved forest and shrubbery forest soils in western Hunan province were studied.The distribution and correlation of heavy metals were analyzed by single factor analysis and principal component analysis.【Result】The coefficient of variation of the contents of five heavy metals in soils under different vegetation is 0.18%-0.69%,and the order from large to small is Cu>Zn>Ni>Pb>CD.The principal component analysis shows that Cu and CD have large load values in PC1 and medium load values in PC2.The results showed that there was a significant negative correlation between soil bulk density and Zn,a significant positive correlation between coniferous soil bulk density and Cu,a significant positive correlation between soil organic matter and CD,a significant positive correlation between coniferous soil pH and Ni and Zn,a significant positive correlation between coniferous soil pH and Pb,Cu and Ni.The correlation between the heavy metal content of shrubbery soil was significant.【Conclusion】The vertical distribution of heavy metals in different vegetation types of soil in western Hunan is different,which shows that the content of heavy metals in the upper soil of coniferous and broad-leaved mixed forest is lower than that in the lower soil,and the content of heavy metals in the upper soil of evergreen broad-leaved forest is higher than that in the lower soil,but there is no difference in the content of heavy metals in coniferous forest and shrub forest;the soil bulk density,organic matter,Slope,pH and thickness of soil layer have a greater impact on CD content,while altitude has a greater impact on Pb,Ni and Cu,and slope has a greater impact on Ni.The possibility of the same source of heavy metals in shrubbery in western Hunan is greater than other three vegetation types.