Water and Heavy Metal Transport in Roadside Soils

B. KOCHER; G. WESSOLEK; H. STOFFREGEN

摘要

Roads with very high traffic loads in regions where soils are low in both pH and sorption capacity might be a source of percolation water loaded with heavy metals. Looking at some "worst case" scenarios, this study focused on the input of traffic related pollutants and on Pb, Cd, Cu, Zn, Ni and Cr concentrations in the soil matrix and soil solution, respectively.The analysis also included pH and electrical conductivity and at some sites DOC. The investigations were carried out on sandy soils with more or less low pH values at four motorway sites in Germany. The average of daily traffic was about 50 000 up to 90 000 vehicles. Soil pore water was collected in two soil depths and at four distances from the road. The pH in general decreased with increasing distance from the roadside. The elevated pH near the roadside was presumably caused by deposition of dust and weathering residues of the road asphalt, as well as by infiltration of salt that was used during winter time. At these road sites, increased heavy metal concentrations in the soil matrix as well as in the soil solution were found. However, the concentrations seldom exceeded reference values of the German Soil Protection Act. The soil solution concentrations tended to increase from the road edge to 10 m distance, whereas the concentration in the soil matrix decreased. Elevated DOC concentrations corresponded with elevated Cu concentrations but did not substantially change this tendency. High soil water percolation rates were found near the roads. Thus, even low metal concentrations of percolation water could yield high metal loads in a narrow area beside the road.

机译：在土壤的pH值和吸附力均较低的地区，交通负荷很高的道路可能是重金属渗入水的来源。着眼于“最坏的情况”，本研究着重于交通相关污染物的输入，以及土壤基质和土壤溶液中Pb，Cd，Cu，Zn，Ni和Cr的浓度。分析还包括pH值和电电导率和某些位置的DOC。调查是在德国四个高速公路站点的pH值较低或较低的沙质土壤上进行的。每天的平均流量约为5万至9万辆。在两个土壤深度和距道路四个距离处收集土壤孔隙水。一般而言，pH值会随着距路边距离的增加而降低。可能是由于路边沥青的灰尘和风化残留物的沉积，以及冬季使用的盐分的渗透，导致路边附近pH升高。在这些道路现场，发现土壤基质以及土壤溶液中重金属的浓度增加。但是，浓度很少超过德国《土壤保护法》的参考值。从道路边缘到10 m距离，土壤溶液浓度趋于增加，而土壤基质中的浓度则下降。 DOC浓度升高与Cu浓度升高相对应，但基本没有改变这种趋势。在道路附近发现土壤水渗透率很高。因此，即使金属浓度低的渗滤水也可能在道路旁的狭窄区域中产生较高的金属负荷。

Water and Heavy Metal Transport in Roadside Soils

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