高速公路沿线农田土壤重金属总量和有效态含量的空间分布特征及其影响因素分析

Spatial Distribution Characteristics of Total and Available Heavy Metal Contents and Their Influencing Factors in Farmland Soils Along Expressway

以沪宁高速为例,选择了车流量不同的三个典型路段,对沪宁高速沿线农田土壤中Pb、Cr、Zn总量和有效态含量的空间分布特征进行了分析。结果表明,沪宁高速沿线农田土壤中存在不同程度的Pb、Cr、Zn累积现象,沿线两侧农田土壤中Pb、Zn总量和有效态含量均随车流量的增加而显著提高。重金属总量和有效态含量的空间插值结果显示,公路两侧农田土壤中Pb含量均随与公路距离的增加而先提高后呈现下降趋势,但相应的Cr、Zn含量与公路距离之间没有明显的相关性。但是,高速公路两侧农田土壤中Pb、Cr、Zn有效态含量与总量的空间分布存在明显差异,表明土壤重金属总量不能完全解释其有效态含量的高低。进一步的相关分析发现,重金属Pb、Cr、Zn的有效态含量与其总量、土壤pH、有机质含量均呈现显著相关关系。可见,除了总量之外,土壤pH和有机质含量也是影响沿线农田土壤中重金属有效态含量空间分布特征的重要因素。

The spatial distribution characteristics of the total and available contents of heavy metals （Pb, Cr, and Zn） in roadside soils were determined in three farming sites with different traffic density along Shanghai-Nanjing Expressway. Results revealed that the traffic activities caused different degrees of heavy metal accumulations in farmland soils along this expressway. The total and available Pb and Zn concentrations in the roadside soils of different sites increased significantly with the traffic density. The spatial interpolation results of the total and available heavy metal contents in the roadside soils showed that the concentrations of Pb in both sides of the expressway initially increased to the maximum values with the distance to the road, and then gradually decreased to the soil background values. While the correlations between the total and available contents of Cr, Zn and the distance to the road sides weren＇t obvious. The spatial distributions of available contents of Pb, Cr, and Zn weren＇t consisted with those of their total contents, indicating that the total content was not the only factor affecting the available contents of these heavy metals. Further correlation analysis showed that there was a significant correlation between the available contents and the total contents, the soil pH and the organic matter, suggesting that soil pH and organic matter were also important factors affecting the spatial distribution of the available contents of heaw metals in the roadside soils.