[Distribution characteristics of heavy metals in soil and its influence on greening plants in a main road of Lanzhou City, Northwest China].

To investigate the characteristics of heavy metal pollution caused by traffic and its potential ecological risks, we measured the amount of metal elements in samples collected from a traffic trunk road in Lanzhou City with atomic absorption spectrophotometer. The single factor index method and potential ecological risk index method were used to evaluate the degree of pollution and potential ecological risks, and then the effects of heavy metal pollution on chlorophyll and calcium (Ca) contents in greening plants were analyzed. The results showed that the amount of heavy metals including chromium (Cr), manganese (Mn), zinc (Zn), copper (Cu) and nickel (Ni) in the soils increased significantly, with Cr, Cu and Pb reaching moderate pollution level. The degree of potential ecological risk was Cu>Pb>Cr>Ni>Zn>Mn. Sophora japonica, Rosa chinesis, Prunus ceraifera, and Euonymus japonicas showed different accumulation effects on Pb, Mn, Zn, and Ni. The content of chlorophyll in the leaves of deciduous species S. japonica, R. chinesis and P. ceraifera was higher in the roadside sampling point than that in the control point, while the pattern was just the opposite in evergreen species E. japonicas and P. orientalis. Foliar Ca content of greening plants in the roadside sampling point was higher than that in the control point, suggesting that high chlorophyll and Ca contents might be beneficial to plant survival in the heavy metal contaminated area. Taken together, traffic operation led to the accumulation of heavy metals (Cr, Mn, Zn, Cu, and Ni) in the soil of the study area. S. japonica, R. chinesis, P. ceraifera and E. japonicas could accumulate Pb, Mn, Zn and Ni, which could be used as greening plants in soils polluted by those heavy metals.