Abstract
Concentrations of four typical heavy metals (Cu; Zn; Cd and Pb) in roadside soils close to three lakes in the Tibetan Plateau were investigated in this study. The hierarchical tree-based regression method was applied to classify concentrations of the heavy metals and analyze their potential influencing factors. It was found that the Tibetan Plateau meadow soils with higher content of sand lead to higher concentrations of Cu; Zn and Pb. The concentrations of Cd and Pb increase with road traffic volume; and for the road segments with higher traffic volume; the Cd and Pb concentrations significantly decrease with the roadside distance. Additionally; the concentrations of Zn and Pb increase as the altitude of sampling site increases. Furthermore; the Hakanson potential ecological risk index method was used to assess the contamination degree of the heavy metals for the study regions. The results show that accumulations of Cu; Zn and Pb in roadside soils remain an unpolluted level at all sites. However; the Cd indices in the regions with higher traffic volume have reached a strong potential ecological risk level; and some spots with peak concentrations have even been severely polluted due to traffic activities.
Highlights
The Tibetan Plateau and surrounding mountains are named the Third Pole of the World due to its high altitude, large area of more than 5 million km2, unique geographical position and special climate environment effect [1,2]
This paper aims to: (1) measure the heavy metal content in roadside soils near plateau lakes and in adjacent regions; (2) analyze the main influencing factors associated with the heavy metal concentrations and distributions; and (3) assess the local heavy metal contamination extent due to vehicle emission
(44.1208 mg/kg) in roadside soils along the NL road segment are obviously higher than other road segments due to higher traffic volume, and they are higher than the background values of
Summary
The Tibetan Plateau and surrounding mountains are named the Third Pole of the World due to its high altitude (over 4,000 m), large area of more than 5 million km, unique geographical position and special climate environment effect [1,2]. The changes of the Tibetan Plateau environment strongly influence its alpine ecosystem and it responds sensitively to global climate change. The environment of the Tibetan Plateau is relatively less affected by anthropogenic interferences because of its natural agricultural structure, low population density and extremely sparse industrial activities owing to current Chinese environmental protection policy. Traffic contaminants are one of the increased concerns in the Tibetan Plateau environment. Studies on heavy metal accumulation caused by road traffic are of great significance to the region’s environmental protection and human health safety.
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