Heavy-Metal Distribution and Concentration of Roadside Soil in the Kathmandu Region, Nepal

摘要

Traffic activities in the roadways are a major resource of the heavy metal contamination in the roadside soil. In this study, the distributions and concentrations of heavy metals (Cu, Zn, Cd, and Pb) in three types of roadside soils are investigated in the Kathmandu region, Nepal. Totally, 342 samples of rural mountainous farmland topsoil, 127 samples of suburban farmland topsoil, and 168 samples of urban roadside dirt topsoil were collected to analyze the factors' effect on roadside heavy metals' distribution and concentration. It is found that in the region, the concentration of heavy metal in the rural farmland topsoil is generally lower than that in the suburban farmland topsoil and urban network dirt topsoil, except for Cd; the heavy metal distributions of the farmland soils in either rural or urban areas are not significantly associated with roadside distance; and the roadside terrain and trees have an important effect on the heavy metal's accumulation process in the soil.