Distribution and pollution assessment of heavy metals in soils on railway side of Shangzhi section of Harbin-Suifenhe railway in northeastern China

Heavy metals (Cu, Zn, Pb and Cd) concentrations using atomic absorption spectrometry were investigated in roadside surface (0-20 cm) and sub-surface (20-40 cm) arable soils along Shangzhi section of Harbin-Suifenhe railway, Heilongjiang province, northeastern China. The soil contamination was assessed on the basis of enrichment factor (EF) and geoaccumulation index (I_geo). The results showed heavy metals in soils 50-meter distance from railway were higher than that of 10- and 100-meter distance. Except for Zn, concentrations of Cu, Pb and Cd in surface soil (0-20 cm) were higher than that of subsurface soil (20-40cm). Concentrations of Cu (17.9 ~ 22.4 mg kg^-1), Zn (106~293 mg kg^-1), Pb (18.2 ~ 24.6 mg kg^-1) and Cd (0.064 ~ 0.386 mg kg^-1) were lower than the values in China National Standards Grade II. Most of EFs of the 4 heavy metals were higher than 1.0. The highest EFs of Cu, Zn, Pb and Cd are 1.23, 5.30, 1.20 and 4.70, respectively. I_geo indicated that Contamination level of Cd was Class 2, Moderately contaminated. There were no obvious pollution of Cu and Pb in the studied area.