# Risk Assessment and Source Apportionment of Heavy Metals in Soils from Handan City
## 3 Results and Discussion
### Spatial Distribution of Soil Heavy Metals  
To further characterize the anthropogenic source, we analyzed the spatial distribution of heavy metals in soil using the ordinary Kriging method. In this process, the distribution of Zn, Cd and Pb was directly obtained, while the spatial distribution of Cr, Mn, Ni and Cu was found using inverse logarithmic transformation. The distributions of seven heavy metal concentrations in soils were shown in Figure 2 and the spatial distribution of heavy metals in soil had obvious characteristics in study area area.  
The distribution of Mn, Zn and Cd contents was similar, and the high content areas were centered on the industrial area (Figure 2a-c). The content distribution of Cr and Ni was very similar, and the high content areas were in the middle and northeast of the research region (Figure 2d,e). The soil samples from the main roads with a high vehicle density (near South Ring Road, Renmin Road and Lianfang East Road) had high Cu and Pb contents (Figure 2f,g). Some studies found that areas with well-developed transportation had high Pb and Cu concentrations in soil [38].  
The spatial distribution map, using the results of the kriging interpolation, offers some information about heavy metals in soil. Southwest Handan has a large concentration of industrial areas. This region has a high number of industrial enterprises, extensive social economic activity, and sizable emissions from steel smelter, coking plant, and traffic. Since the spatial distributions of Zn, Cd and Pb were mainly concentrated in the southwest area of Handan, it was speculated that Zn, Cd and Pb in soil were usually affected by industrial and traffic activities. This is similar to the previously published research in China. The research carried out by [PERSON] et al. (2016) found a significant positive correlation between the concentrations of Pb and Zn in soil and traffic emissions in Changsha. Industrial activities were also associated with the concentration of Cd [45].  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline  & **Cr** & **Mn** & **Ni** & **Cu** & **Zn** & **Cd** & **Pb** \\ \hline Maximum (mg\(\cdot\)kg\(-\)1) & 471.39 & 1149.65 & 151.29 & 225.95 & 346.83 & 2.52 & 110.68 \\ Median (mg\(\cdot\)kg\({}^{-1}\)) & 77.89 & 571.20 & 40.64 & 29.15 & 135.39 & 0.82 & 30.27 \\ Minimum (mg\(\cdot\)kg\({}^{-1}\)) & 9.41 & 458.60 & 12.87 & 7.35 & 73.20 & 0.12 & 2.21 \\ Mean (mg\(\cdot\)kg\({}^{-1}\)) & 94.40 & 588.25 & 47.47 & 43.16 & 158.32 & 0.92 & 33.27 \\ Standard deviation (mg\(\cdot\)kg\({}^{-1}\)) & 78.35 & 100.57 & 29.19 & 42.22 & 69.15 & 0.53 & 18.70 \\ Background of Hebe (mg\(\cdot\)kg\({}^{-1}\)) & 68.3 & 608 & 30.8 & 21.8 & 78.4 & 0.094 & 21.5 \\ Coefficient of variation (\(CV\)) & 0.83 & 0.17 & 0.61 & 0.98 & 0.44 & 0.58 & 0.56 \\ Skewness & 2.785 & 3.300 & 2.098 & 3.021 & 1.013 & 1.273 & 1.209 \\ Kurtosis & 9.874 & 15.723 & 4.584 & 9.794 & 0.231 & 1.584 & 3.525 \\ Kolmogorov–Smirnov test (\(P\)) & 0.004 & 0.012 & 0.003 & 0.000 & 0.142 & 0.120 & 0.156 \\ \hline \end{tabular}
\end{table}
Table 1: Statistical analysis of heavy metals in the soils of the study area.  
Figure 2: Spatial distributions of seven heavy metals in the soil of the study area. (**a**–**g**) stands for the Mn, Zn, Cd, Cr, Ni, Cu and Pb, respectively.