## 3 Results
### Heavy Metal Content in Various Parts and Growth Stages of American Ginseng  
The content of Cu, Mn, As, Pb, Cd, Cr, and Ni in the taproots, lateral roots, and reed head of American ginseng was significantly different over various growth periods (Figure 1). In annual American ginseng, Cu, Cr, and Ni were mainly concentrated in the taproots, with average concentrations of 2.60, 1.78, and 7.35 mg/kg, respectively. Mn, Pb, and As were mainly concentrated in the lateral roots, with average concentrations of 139.16, 101.95, and 79.66 mg/kg, respectively. Interestingly, in biennial American ginseng, Mn, As, and Pb were concentrated in the reed head, with average concentrations of 312.96, 17.58, and 27.00 mg/kg, respectively. Cu and Ni accumulated in both taproots and lateral roots, with average concentrations of 5.70 and 4.82 (taproots) and 7.76 and 5.61 (lateral roots) mg/kg, respectively. Mn and As were still mainly accumulated in the reed head, with average concentrations of 340.74 and 6.98 mg/kg, respectively. In triennial American \begin{table}
\begin{tabular}{l c c c c c c c c c c c c c c} \hline  & **AG\_As** & **AG\_Cd** & **AG\_Cr** & **AG\_Cu** & **AG\_Mn** & **AG\_Ni** & **Soil\_As** & **Soil\_Cd** & **Soil\_Cr** & **Soil\_Cu** & **Soil\_Mn** & **Soil\_Ni** & **Soil\_Pb** \\ \hline \hline \(\text{AG}\)\(\_\)As & 1.000 & & & & & & & & & & & & & \\ \(\text{AG}\)\(\_\)Cd & \(-0.420\) & 1.000 & & & & & & & & & & & & \\ \(\text{AG}\)\(\_\)Cr & 0.228 & \(-0.058\) & 1.000 & & & & & & & & & & & \\ \(\text{AG}\)\(\_\)Cu & \(-0.204\) & 0.416 & \(-0.196\) & 1.000 & & & & & & & & & & \\ \(\text{AG}\)\(\_\)Mn & \(-0.303\) & 0.859 \({}^{\ast}\) & 0.182 & 0.530 & 1.000 & & & & & & & & & \\ \(\text{AG}\)\(\_\)Ni & \(-0.262\) & 0.732 \({}^{\ast}\) & 0.320 & 0.265 & 0.735 \({}^{\ast}\) & 1.000 & & & & & & & & \\ \(\text{Soil}\)\(\_\)As & \(-0.233\) & \(-0.429\) & 0.330 & \(-0.143\) & \(-0.371\) & \(-0.180\) & 1.000 & & & & & & & \\ \(\text{Soil}\)\(\_\)Cd & 0.021 & \(-0.258\) & 0.078 & 0.099 & 0.080 & 0.156 & 0.695 \({}^{\ast}\) & 0.999 & & & & & & \\ \(\text{Soil}\)\(\_\)Cr & 0.202 & \(-0.488\) & \(-0.138\) & \(-0.241\) & \(-0.334\) & \(-0.544\) & 0.422 & 0.420 & 1.000 & & & & & \\ \(\text{Soil}\)\(\_\)Cu & \(-0.403\) & 0.101 & \(-0.774\) & \(-0.423\) & 0.067 & \(-0.210\) & 0.509 & 0.319 & 0.252 & 1.000 & & & & \\ \(\text{Soil}\)\(\_\)Mn & 0.155 & \(-0.540\) & 0.226 & \(-0.153\) & \(-0.419\) & \(-0.383\) & \(-0.066\) & \(-0.026\) & 0.085 & \(-0.342\) & 1.000 & & & \\ \(\text{Soil}\)\(\_\)Ni\(\_\)N & 0.164 & \(-0.707\) \({}^{\ast}\) & \(-0.135\) & \(-0.370\) & \(-0.604\) \({}^{\ast}\) & \(-0.601\) \({}^{\ast}\) & 0.521 & 0.449 & 0.874 \({}^{\ast}\) & 0.223 & 0.324 & 1.000 & & & \\ \(\text{Soil}\)\(\_\)Pb & \(-0.097\) & \(-0.536\) & \(-0.062\) & \(-0.106\) & \(-0.351\) & \(-0.420\) & 0.446 & 0.490 & 0.664 \({}^{\ast}\) & 0.256 & 0.585 \({}^{\ast}\) & 0.848 \({}^{\ast}\) & 1.000 \\ \hline \end{tabular}
\end{table} 
Table 4: Correlation coefficients of heavy metal content between American ginseng and planting soil. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c c} \hline  & **YG1** & **YG2** & **YG3** & **BG1** & **BG2** & **BG3** & **NG1** & **NG2** & **NG3** & **CG1** & **CG2** & **CG3** & **Min** & **Max** & **Average** \\ \hline Cu & 0.23 & 0.21 & 0.14 & 0.17 & 0.34 & 0.24 & 0.27 & 0.29 & 0.32 & 0.37 & 0.22 & 0.34 & 0.14 & 0.37 & 0.26 \\ Mn & 0.02 & 0.03 & 0.02 & 0.08 & 0.07 & 0.08 & 0.35 & 0.25 & 0.39 & 0.16 & 0.10 & 0.03 & 0.02 & 0.39 & 0.13 \\ As & 0.13 & 0.00 & 0.14 & 0 ginseng, the content of Pb was very little. Cu and Ni were slightly accumulated in the taproots, lateral roots, and reed head. Cr accumulated in the lateral roots and reed head for the first time in the 3 year growth of American ginseng, with an average content of 0.94 and 1.35 mg/kg, respectively. In addition, most of the heavy metals in this study were easily accumulated in the reed head in the third year. The heavy metal content was compared with the LSVs of Chinese medicinal material.