# Risk Assessment of Soil Heavy Metals in the Jiahe River Basin of Yantai City, China
## 4 Discussion
### Assessment Results in the Jiahe River Basin  
The pollution risk of heavy metal in the Jiahe River Basin of Yantai City was assessed using the criteria of GB15618-2018 with I\({}_{\text{geo}}\) as a supplement for metals without criteria. Specifically, the following assessment approaches were employed: (1) Cd, Hg, As, Pb, and Cr were assessed using GB15618-2018, which is presented in Equation (1); (2) samples with concentrations of Cu, Ni, and Zn lower than the risk screening values were also evaluated using GB15618-2018, which is detailed in Equation (1); (3) samples with contents of Cu, Ni, and Zn exceeding the risk screening values were assessed using the newly established I\({}_{\text{geo}}\), which is described in Equation (6); and (4) Co, V, and Mn were assessed using Equation (6).  
The assessment results of the pollution risk of heavy metals in agricultural soils in this area are presented in Table 3. Hg and Pb were at the background level in all samples. Cr, Ni, Zn, Co, V, and Mn were at the background level, except for a few samples at the screening level. Cu, As, and Cd were basically at the background level, except for some samples at the screening level. In other words, the overall pollution risk of heavy metals in the agricultural soils in the Jiahe River Basin was at the background level. Specifically, Hg and Pb in the whole area were at the background level. There were sporadic areas at the screening level for Cr, Ni, Zn, Co, V, and Mn, while some regions were at the screening level for Cu, As, and Cd. No heavy metals were at the intervention level in this area.  
The aforementioned assessment results are only statistical results and do not indicate the spatial distribution. To spatially illustrate the pollution risk of heavy metals in the study area, the assessment results from Equation (6) were mapped as shown in Figure 3. The results in Figure 3 are consistent with the statistical results that only Cu, As, and Cd were clearly at the screening level. Specifically, the regions with Cu at the screening level were mainly in the north part of the area; the screening regions of As were mainly distributed in the north and south parts; and the screening regions of Cd were found in many parts of the study area.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**Evaluation Method** & **Risk Level** & **Cd** & **Hg** & **As** & **Pb** & **Cr** & **Cu** & **Ni** & **Zn** & **Co** & **V** & **Mn** \\ \hline \multirow{4}{*}{PI} & 0 (background level) & 176 & 213 & 194 & 213 & 211 & 195 & 211 & 211 & - & - & - \\  & 1 (screening level) & 37 & 0 & 19 & 0 & 2 & - & - & - & - & - & - \\  & 10 (intervention level) & 0 & 0 & 0 & 0 & 0 & - & - & - & - & - \\ \hline \multirow{4}{*}{I\({}_{\text{geo}}\)} & 0 (background level) & - & - & - & - & - & - & - & - & 209 & 210 & 212 \\  & 1 (screening level) & - & - & - & - & - & 18 & 2 & 2 & 4 & 3 & 1 \\ \cline{1-1}  & 10 (intervention level) & - & - & - & - & - & 0 & 0 & 0 & 0 & 0 & 0 \\ \hline \end{tabular}
\end{table}
Table 3: Assessment results of \(11\) heavy metals in agricultural soils of the Jiahe River Basin of Yantai City.