# Analysis of Heavy Metal Sources in Xutuan Mining Area Based on APCS-MLR and PMF Model
## 3 Results and Discussion  
### Distributions of the Water and Sediment Heavy Metal Contents  
The observed heavy metal concentrations in the water bodies in the coal mining subsidence areas are shown in Table 2. The average Cu, Cr, Cd, Zn, Pb, and As concentrations in the water body in the study area were 6.28, 37.26, 0.41, 26.15, 2.29, and 32.86 ug.L\({}^{-1}\), respec  
Figure 2: Experimental flow chart. tively. According to China's surface water environmental quality standard (GB3838-2002), the average Cu, Pb, Zn, Cd, and As concentrations met the national Class I water quality standard limits of 10, 10, 50, 1, and 50 ug\(\cdot\)L\({}^{-1}\), respectively, indicating the lack of associated pollution. However, Cr exceeded and met the national Class I and Class II water quality standard limits of 10 and 50 ug\(\cdot\)L\({}^{-1}\), respectively. Generally, our results revealed a lack of water heavy metal pollution. The pH range of the water in the mining area is 5.96-8.35. The average value is 7.19. The water body in the mining area is weakly alkaline. The results show that the pH value is the main factor affecting the adsorption characteristics of heavy metals, and the acidic to neutral environment promotes the desorption of heavy metal ions [30]. The maximum, minimum, mean, standard deviation, and coefficient of variation values of the six heavy metal elements in the sediments were determined and then compared with the soil background values of the Xutuan mining area and the national soil Class II standards (Table 3). The obtained results showed lower Cu, Cr, Zn, and Pb contents than the soil background values in the Xutuan mining area, except for Cd and As. Among them, Cd was 17 and 3.3 times higher than the corresponding background and national soil Class II standard values, respectively, whereas the As contents were 4 and 1.3 times higher than the background and national Class II soil standard values, respectively. These findings indicate the enrichment of Cd and As in the sediments of the study area. The concentration of Cd in the sediment of the mine was significantly lower than that in the sediment of Aqyazi River in Iran near the iron ore mine (1.31 mg/kg \(<\) Cd \(<\) 8.01 mg/kg). However, the concentration of As was higher than that of the river sediment (1.57 mg/kg \(<\) As \(<\) 2.57 mg/kg) [32]. The concentrations of As and Cd were lower than those in Yujiang sediments, a polymetallic ore concentration area in China [33]. As a dimensionless expression of standard deviation, \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & **Mean** & **SD** & **CV.** & **Minimum** & **Maximum** & \multicolumn{2}{c}{**Chinese National Standards ***} & \% of SER \\ \hline Cu & 6.28 & 1.77 & 0.28 & 3.26 & 11.05 & 1000 & 0.00 \\ Cr & 37.26 & 8.91 & 0.24 & 24.15 & 65.79 & 50 & 10.00 \\ Cd & 0.41 & 0.33 & 0.81 & BDL & 1.68 & 5 & 0.00 \\ Zn & 26.15 & 15.19 & 0.58 & 9.79 & 89.92 & 1000 & 0.00 \\ Pb & 2.29 & 1.03 & 0.45 & 0.89 & 4.96 & 50 & 0.00 \\ As & 32.86 & 23.25 & 0.71 & BDL & 104.25 & 50 & 20.00 \\ pH & 7.19 & 0.73 & 0.10 & 5.96 & 8.35 & & \\ \hline \end{tabular}
\end{table} 
Table 2: Descriptive statistics of the heavy metal (ug\(\cdot\)L\({}^{-1}\)) element contents in the water. \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & **Maximum** & **Minimum** & **Mean** & **SD** & **CV** & **Background Values** & **Level II Standards** \\ \hline Cu & 23.12 & 10.79 & 16.44 & 3.02 & 0.18 & 22.6 & 100 \\ Cr & 73.56 & 34.92 & 51.89 & 9.94 & 0.19 & 60.6 & 250 \\ Cd & 2.80 & 1.28 & 1.98 & 0.43 & 0.22 & 0.1162 & 0.6 \\ Zn & 50.74 & 28.15 & 37.29 & 6.07 & 0.16 & 47.3 & 300 \\ Pb & 25.58 & 10.77 & 16.42 & 4.20 & 0.26 & 24.6 & 350 \\ As & 46.25 & 15.89 & 31.49 & 8.11 & 0.26 & 7.8 & 25 \\ pH & 7.65 & 6.10 & 7.09 & 0.39 & 0.05 & & \\ OM & 10.05 & 5.14 & 7.24 & 1.32 & 0.18 & & \\ \hline \end{tabular}
\end{table} 
Table 3: Descriptive statistics of the heavy metal (mg/kg) element contents in the sediments.