[Accumulation and potential risk of heavy metals in roadside soils along the section of Zhengzhou-Shangqiu, Lianyungang-Huoerguosi highway].

Two typical sampling transects along the Zhengzhou-Shangqiu section, Lianyungang-Huoerguosi highway,were chosen to investigate the accumulation of heavy metals in roadside soils. The highway section at Wanliu transect has been operated since 1994, and that at Xiaowangzhuang section since 2001. Soil samples were collected along the two transects according to the distances from the highway. In laboratory, the concentrations of Cd, Cu, Pb, Zn, Ni and Cr in the soils were measured using AAS. The accumulation of these metals in roadside soils is analyzed in terms of annual accumulation rates and fluxes. The spatial patterns and potential risk of the metals are also discussed. There are several findings in this case study. Along the two transects, the concentrations of Cd, Cu and Pb in the soils increase from the highway first, and then decrease to the control values gradually. So they are typical traffic-source (anthropogenic) heavy metals. In contrast, Cr, Ni and Zn are nature-source metals. The highest concentrations of the anthropogenic metals in the soils occur between 25-50 m from the highway. The average valuesof concentration of Pb, Cu and Cd in the soils along Wanliu transect are 14.52 mg x kg(-1), 1.32 mg x kg(-1), and 73.54 mg x kg(-1) respectively, and 12.41 mg x kg(-1), 0.98 mg x kg(-1), and 43.64 mg x kg(-1) along Xiaowangzhuang transect respectively. The annual accumulation rates and fluxes of Pb, Cu and Cd in most samples are positive, Cu > Pb > Cd, and the values on Xiaowangzhuang transect are higher than those on Wanliu transect. Potential risk of Cd in all sample are negative, indicating that the soils have been polluted by Cd. In contrast, potential risk of Cu and Pb in most sample sites are positive, but the potential risk of Cu in the soils is much higher than that of Pb. Most sample sites within 300 m from the highway should be polluted by Cu in the future of five to thirty years, but polluted by Pb in the future of many more than one thousand years.