干旱风沙区路域柠条灌丛林地土壤重金属分布及其与土壤分形维数的关系

Distribution of Soil Heavy Metal Contents in Caragana korshinskii Shrub Habitats on the Proximity of Expressway and Its Relationship With Soil Fractal Dimension in Deserted Region

为了解干旱风沙区路域柠条林地土壤重金属的分布特征,探究其与不同粒径土壤颗粒和土壤分形维数的相关关系,为公路旁柠条林地土壤污染评价提供参考。以青银高速旁人工柠条林地为研究样地,调查了距高速公路0,30,60,100,150,200m灌丛林下表层土壤重金属Pb,Cu,Cd,Zn含量,并对土壤重金属含量与土壤粒径分布及土壤分形维数进行了相关分析。结果表明:(1)0~200m,土壤重金属Pb,Cu,Cd,Zn变化曲线均呈"单峰"型,峰值分别出现在150,30,0,60m处。(2)随着距高速公路距离的增加,土壤黏粒含量呈上升趋势,而极细砂粒呈下降趋势;土壤分形维数呈缓慢上升趋势。(3)相关分析显示,土壤Cd和Zn在土壤黏粒中存在明显富集作用,而土壤Pb和Cu在各粒径颗粒中均无富集作用。土壤Pb,Cu,Cd,Zn与土壤分形维数间均未表现出相关性(p>0.05),而土壤黏粒(r=0.71,p<0.05)和极细砂粒(r=0.73,p<0.05)与土壤分形维数间均表现出线性相关关系。研究表明,干旱风沙区路域柠条灌丛林不同种类土壤重金属空间分布变化较大,且存在阈值。土壤粒径较小的黏粒更容易吸附重金属,其分布特点对路域土壤重金属扩散范围的研究有重要的参考意义。并且,土壤分形维数变化能够反映该区土壤理化性状的变化特征,可以将其作为路域土壤结构、土壤退化恢复程度的一个定量指标。

In order to understand the distributions of heavy metals in Caragana korshinskii shrub habitats nearby expressway in deserted region,an investigation on soil heavy metal content and its relationship with different size of particles and fractal dimension of soil particles at the distances of 0,30 m,60 m,100 m,150 m and 200 m away from expressway,respectively,was carried.It was showed that:(1)there was a‘single peak,type for soil Pb,Cu,Cd,and Zn contents spatially ranging from 0 m to 200 m away from expressway,with the peaks at the distances of 150 m,30 m,0 m,60 m,respectively;(2)with the increase of the distance from the expressway,soil clay contents increased,while soil fine sand contents decreased;the soil fractal dimension was found to present the slowly increasing trend;(3)the correlation analysis showed that there was a significant enrichment of soil Cd and Zn in clay,whereas there was no enrichment of soil Pb and Cu regarding in the particle sizes;there was no correlation between soil Pb,Cu,Cd,Zn and soil fractal dimension,while there was a linear correlation between soil clay,fine sand and soil fractal dimension,suggesting that there was remarkable changes of soil heavy metal contents on the proximity of expressway in shrub soil habitats.There was a strong accumulation of soil metals in clay fraction,which had the implications on diffusion range of soil heavy metal nearby expressway;in addition,the change of soil fractal dimension could characterize the soil physical and chemical properties in this deserted region.