(5)
In formula (2) (3) (4), RIE is the relative impact equivalent of soil; m is the stable oxidation value of element i (Cu: 2; Zn: 2; Pb 2; Cd: 2; As: 5; Hg: 2; Cr: 3, and Ni: 2) (Wang et al., 2016);DDDB is the deviation degree between the detected and background values; Pbi is the determined concentration of element i that exceeds the geological background concentration in the soil; Cbi is the geological background concentration of element i .
2.4 Data and statistical analysis
The normal distribution of the HMs concentrations in soils was examined by the one-sample Kolmogorov-Smirnov test. Data were processed with Microsoft Excel 2016. Principal component factor and Pearson correlation analysis were performed with SPSS 18.0 software. One-way variance and least significant difference (LSD) were employed to find data significance. Linear correlation results were plotted with Origin Pro 9.1 (64 Bit) program.