# Risk Assessment of Soil Heavy Metals in the Jiahe River Basin of Yantai City, China
## 3 Results
### Risk Assessment Using GB15618-2018  
According to GB15618-2018, agricultural land is categorized into three types: paddy fields, orchards, and other agricultural land. In the study area, land use includes two types, which are orchards and other agricultural land. After the land use types are determined, GB15618-2018 provides criteria for risk assessments of heavy metals based on different pH levels. That is to say, three risk levels are classified for land use types and pH levels in GB15618-2018: background level, screening level, and intervention level [28]. According to [PERSON] et al. [28], the PI (or the single pollution index) for heavy metals in soils of agricultural land, based on GB15618-2018, is presented as follows:  
\[\text{PI}= \begin{cases}0&\text{C}<\text{C}_{\text{RS}},\quad\text{ the background level}\\ 1&\text{C}_{\text{RS}}\leq\text{C}<\text{C}_{\text{RI}},\text{ the screening level}\\ 10&\text{C}_{\text{RI}}\leq\text{C},\text{ the intervention level}\end{cases}  \tag{1}\]  
where C represents the concentration of a heavy metal in soil samples, and C\({}_{\text{RS}}\) and C\({}_{\text{RI}}\) are its risk screening value and risk intervention value specified in GB15618-2018 for different land use types and pH levels (Table A1). Based on Equation (1), the PI values of five heavy metals (Cd, Hg, As, Pb, and Cr) for 213 soil samples from the study area were calculated, and their counts on each level are listed in Table 2. It is worth noting that no intervention-level values for Cu, Ni, and Zn are presented in GB15618-2018, except only screening-level values. Furthermore, Co, V, and Mn are not mentioned in GB15618-2018. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**No.** & **Item** & **Min.** & **Q\({}_{1}\)** & **Q\({}_{2}\)** & **Q\({}_{3}\)** & **Max.** & **Avg.** & **Avg.\({}_{-}\)cn** \\ \hline
1 & Cd & 40 & 130 & 204 & 285 & 1820 & 202 & 150 \\
2 & Hg & 5 & 22.45 & 32 & 46.85 & 542 & 33 & 50 \\
3 & As & 1.6 & 8.67 & 12.9 & 19.75 & 79.1 & 12.9 & 9.1 \\
4 & Pb & 9.26 & 21.7 & 26.59 & 30.15 & 117.7 & 26 & 25 \\
5 & Cr & 26.2 & 60.57 & 72.72 & 85.74 & 214.5 & 73 & 63 \\
6 & Cu & 10.3 & 26.81 & 34.4 & 46 & 448.4 & 37 & 23 \\
7 & Ni & 13.7 & 27.27 & 33.45 & 41.05 & 89.17 & 34 & 26 \\
8 & Zn & 39.6 & 72.44 & 82.21 & 102.1 & 569.5 & 85 & 67 \\
9 & Co & 6.47 & 13.34 & 15.71 & 18.33 & 45.1 & 15.8 & 11.7 \\
10 & V & 48 & 82.87 & 93.81 & 108.5 & 274.8 & 94 & 79 \\
11 & Mn & 230 & 470.5 & 571 & 675.4 & 2071 & 575 & 552 \\
12 & pH & 4.44 & 5.8 & 6.3 & 7.04 & 9.01 & 6.42 & — \\ \hline \end{tabular} Note: The number of samples was 213. The units of concentrations are mg/g, except for Cd and Hg, which are in mg/g. Q\({}_{1}\), Q\({}_{2}\), and Q\({}_{3}\) represent the first, second, and third quartiles of the concentrations and pH. Avg. is the geometric mean calculated without outliers, and Avg\({}_{-}\)cn refers to the element abundance of surface soil in China [27].  
\end{table} 
Table 1: Statistical parameters of heavy metal concentrations and pH. For the five heavy metals--Cd, Hg, As, Pb, and Cr--with screening and intervention values in GB15618-2018, no samples with PI values of 10 were found in this area. The PI values for Hg and Pb were 0 in all of the 213 samples. For Cr, As, and Cd, there were 2, 19, and 37 samples, respectively, with a PI value of 1. These results indicate that Hg and Pb in this area are at the background level; Cr, As, and Cd basically belong to the background level except for a few samples. Regarding the three heavy metals--Cu, Ni, and Zn--with only screening-level values in GB15618-2018, it was found that 211 samples of Ni and Zn, as well as 195 samples of Cu, had PI values of 0. That is to say, only a few samples of Cu, Ni, and Zn among the 213 samples were not at the background level. Because the three heavy metals Co, V, and Mn are not mentioned in GB15618-2018, their risk assessment is not discussed here using the criteria in GB15618-2018. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  
\end{table}