## 3 Results and Discussion
### Soil Quality Assessment
#### 3.2.2 Evaluation by Pollution Indices  
The values and descriptive statistics of the selected pollution indices are shown in Table 5. For this study, we used Sc as the reference element because of its abundance and stability in the upper continental crust, its uniformity across the entirety of the study area, and its effective use in prior studies [94, 96, 97]. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & & **As** & **Cd** & **Cr** & **Cu** & **Hg** & **Ni** & **Pb** & **Zn** & **PTEs** \\ \hline \multirow{2}{*}{\(<\)RSV} & number & 1147 & 1291 & 1353 & 1311 & 1514 & 1388 & 1511 & 1522 & 805 \\  & percentage & 72.87\% & 82.02\% & 85.96\% & 83.29\% & 96.19\% & 88.18\% & 96.00\% & 96.70\% & 51.14\% \\ \multirow{2}{*}{RSV-RIV} & number & 415 & 274 & 221 & 263 & 56 & 186 & 57 & 52 & 743 \\  & percentage & 26.37\% & 17.41\% & 14.04\% & 16.71\% & 0.25\% & 11.82\% & 3.30\% & 3.30\% & 47.20\% \\ \multirow{2}{*}{\(>\)RIV} & number & 12 & 9 & 0 & 0 & 0 & 0 & 6 & 0 & 26 \\  & percentage & 76.00\% & 0.57\% & 0.00\% & 0.00\% & 0.00\% & 0.38\% & 0.00\% & 1.65\% \\ \hline \end{tabular} Notes: RSV, the risk screening values for soil contamination of agricultural land of China [95]; RIV, the risk intervention values for soil contamination of agricultural land of China [95].  
\end{table} 
Table 4: The number and percentage of sites over the national environmental quality of PTEs. Figure 2: The distribution of soil environmental quality based on the risk control standard for soil contamination of agricultural land of China. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \multicolumn{6}{c}{EF} \\ \hline  & As & Cd & Cr & Cu & Hg & Ni & Pb & Zn \\ \hline Mean & 1.32 & 2.14 & 1.07 & 1.08 & 1.70 & 1.00 & 1.62 & 1.21 \\
25 th & 0.62 & 1.09 & 0.95 & 0.88 & 0.62 & 0.85 & 0.93 & 0.90 \\ Median & 0.96 & 1.56 & 1.05 & 1.00 & 1.01 & 0.95 & 1.31 & 1.10 \\
75 th & 1.52 & 2.30 & 1.16 & 1.15 & 1.74 & 1.10 & 1.68 & 1.33 \\ Min & 0.01 & 0.35 & 0.28 & 0.23 & 0.04 & 0.29 & 0.07 & 0.32 \\ Max & 49.51 & 32.14 & 3.14 & 16.06 & 75.48 & 5.54 & 62.66 & 17.47 \\ Standard deviation & 1.73 & 2.50 & 0.21 & 0.68 & 3.51 & 0.29 & 3.03 & 0.85 \\ Variance & 3.01 & 6.23 & 0.04 & 0.46 & 12.34 & 0.08 & 9.19 & 0.72 \\ Skewness & 15.02 & 6.56 & 1.47 & 13.97 & 11.62 & 4.74 & 15.35 & 10.54 \\ Kurtosis & 384.02 & 58.43 & 9.34 & 252.40 & 185.17 & 55.95 & 274.19 & 160.46 \\ \hline \multicolumn{7}{c}{Igeo} \\ \hline  & As & Cd & Cr & Cu & Hg & Ni & Pb & Zn \\ \hline Mean & \(-0.75\) & \(0.05\) & \(-0.60\) & \(-0.65\) & \(-0.60\) & \(-0.73\) & \(-0.38\) & \(-0.54\) \\
25 th & \(-1.47\) & \(-0.53\) & \(-0.97\) & \(-1.08\) & \(-1.34\) & \(-1.11\) & \(-0.76\) & \(-0.83\) \\ Median & \(-0.78\) & \(-0.07\) & \(-0.66\) & \(-0.74\) & \(-0.68\) & \(-0.76\) & \(-0.45\) & \(-0.58\) \\
75 th & \(-0.07\) & \(0.52\) & \(-0.24\) & \(-0.24\) & \(0.03\) & \(-0.31\) & \(-0.09\) & \(-0.31\) \\ Min & \(-5.81\) & \(-3.71\) & \(-4.16\) & \(-4.44\) & \(-5.44\) & \(-4.56\) & \(-3.38\) & \(-2.42\) \\ Max & 5.02 & 4.77 & 1.24 & 3.27 & 5.34 & 2.06 & 5.52 & 3.69 \\ Standard deviation & 1.10 & 0.94 & 0.58 & 0.68 & 1.19 & 0.65 & 0.76 & 0.56 \\ Variance & 1.21 & 0.88 & 0.34 & 0.47 & 1.42 & 0.43 & 0.58 & 0.31 \\ Skewness & 0.15 & 0.97 & \(-0.26\) & 0.17 & 0.75 & \(-0.28\) & 1.79 & 1.50 \\ Kurtosis & 1.02 & 2.88 & 2.50 & 3.23 & 2.21 & 1.75 & 10.42 & 8.34 \\ \hline \multicolumn{7}{c}{C\({}_{\rm f}\)} \\ \hline  & As & Cd & Cr & Cu & Hg & Ni & Pb & Zn \\ \hline Mean & 1.23 & 2.06 & 1.07 & 1.08 & 1.58 & 1.00 & 1.47 & 1.14 \\
25 th & 0.54 & 1.04 & 0.77 & 0.71 & 0.59 & 0.69 & 0.88 & 0.84 \\ Median & 0.87 & 1.43 & 0.95 & 0.90 & 0.93 & 0.88 & 1.10 & 1.00 \\
75 th & 1.43 & 2.15 & 1.2 There was no significant enrichment or contamination with the studied PTEs in the surface soils in the study area, based on the average (mean) and median values of EF, Igeo, and Cf that were obtained (Table 5). With the exception of Cr, the rest of the PTEs studied in this area showed significant to extremely high enrichment by the indicated EF in some locations.