Spatial Distribution and Potential Ecological Risk Assessment of Heavy Metals in Roadside Soils along the Lianyungang-Horgas Highway

On Lianyungang-Horgas highway,two typical sampling transects along the Zhengzhou-Shangqiu section,Wanliu transect operated in 1994 and Xiaowangzhuang transect operated in 2001,were chosen to investigate the distribution and potential ecological risks of heavy metals(Cd,Cu,Pb,Zn,Ni,and Cr) in roadside soils.Soil samples were collected at different distances from the highway.The contents and spatial distribution of heavy metals in the soils were analyzed.The ecological risks of soil heavy metals were evaluated based on potential ecological risk index(RI) put fowward by H kanson.The results show that heavy metal concentrations and potential ecological risks on Wanliu transect(at moderate ecological risk level) were higher than those on Xiaowangzhuang transect(at slight ecological risk level) because of longer operated time.Most of the heavy metal concentrations and potential ecological risks present a skew distribution with the distance from highway roadbed.The highest risk indexes for different metals on Wanliu transect are observed at 50～100 m from highway roadbed,while those on Xiaowangzhuang transect at 35 m from the roadbed.The total risk index was mainly contributed by cadmium with the averagely proportion of 61.39%(ECd/RI).Therefore cadmium is the main factor influencing potential ecological risks.Potential ecological risk index is a rigorous method,because it includes not only concentrations of heavy metals,but also ecological effects and toxicological characters.To apply the method of RI in estimating the potential ecological risk of pollutants,the RI standards for different levels of potential ecological risk should be modified according to the pollutant amounts studied and their toxic-response factors.