## 3 Results and Discussion
### Bioconcentration and Translocation Factors  
The bioconcentration factor is one of the main indicators of the phytoremediation efficiency of a plant; it is an indicator of the ability of the plant to accumulate HMs from the soil [62]. Table 8 provides the BCF calculation results for sweet potato grown in three contaminated fields. The sweet potato tuber BCFs for Zn in Fields 1, 2, and 3 were 18.08, 35.77, and 0.85, respectively. This correlated with the results for the leaf BCF, which were 12.18, 17.72, and 1.34, respectively. A lower absorption of Zn was observed for Field 3 and higher for Fields 1 and 2. Brown rice used as a food plant in South Korea showed a low BCF [63], but plants such as _Corchorus olivorius_ and _Solanum nigrum_ had a Zn BCF greater than 1 [64]. BCF and TF also depended on sweet potato varieties, where authors showed the effectiveness of phytoremediation properties of sweet potatoes lead removal efficiencies by kg/ha. Also, the process has been accelerated with the addition of fertilizer to obtain more yields, correspondingly more accumulation of HM. HM accumulation and transfer mechanisms at the whole plant level in these plants depend on several processes: tuber metal uptake, translocation between roots and aerial parts, transport to deciduous organs or less active tissues or cell types, and transfer to seeds [44].  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Field**} & \multirow{2}{*}{**Depth (cm)**} & \multicolumn{3}{c}{**Pb**} & \multicolumn{3}{c}{**Zn**} & \multicolumn{3}{c}{**Cd**} \\ \cline{2-11}  & & \(C_{f}\) & \(I_{geo}\) & \(E_{r}\) & \(C_{f}\) & \(I_{geo}\) & \(E_{r}\) & \(C_{f}\) & \(I_{geo}\) & \(E_{r}\) \\ \hline \multirow{2}{*}{1} & 5 & 2.05 & 7.32 & 10.25 & 1.22 & 9.05 & 1.22 & 0.95 & 5.37 & 28.59 \\  & 15 & 0.46 & 5.15 & 2.29 & 0.15 & 6.04 & 0.15 & 0.50 & 4.44 & 15.02 \\ \multirow{2}{*}{2} & 5 & 0.51 & 5.31 & 2.56 & 1.88 & 9.67 & 1.88 & 0.83 & 5.17 & 24.87 \\  & 15 & 0.25 & 4.28 & 1.25 & 0.97 & 8.71 & 0.97 & 0.74 & 5.01 & 22.19 \\ \multirow{2}{*}{3} & 5 & 1.42 & 6.78 & 7.09 & 5.90 & 11.32 & 5.90 & 2.54 & 6.79 & 76.28 \\  & 15 & 0.49 & 5.26 & 2.47 & 4.30 & 10.86 & 4.30 & 1.80 & 6.29 & 54.13 \\ \multirow{2}{*}{control} & 5 & 0.30 & 4.57 & 1.52 & 1.01 & 8.78 & 1.01 & 0.80 & 5.11 & 23.94 \\ \multirow{2}{*}{15} & 5 & 0.20 & 3.99 & 1.02 & 0.15 & 5.97 & 0.15 & 0.39 & 4.10 & 11.82 \\ \hline \hline \end{tabular}
\end{table}
Table 6: HM concentrations of mine tailings, soils, and sweet potatoes.  
The BCFs for Cd were 0.3 and 0.08 for Fields 2 and 3, respectively. These values indicated low HM accumulation. However, there was a clear correlation between the decrease in the BCF and the increase in the TIF of the plant. There were high values for Cd in the leaves compared with the tuber, with a TF of 2.31 indicating active movement of metal ions in the plant, and similar dynamics were observed in four species of _Brassica_[44]. The opposite dynamic was observed in a study of _Virginia fumptals_[65].  
Pb val values for Fields 1, 2, and 3 were 10.5, 9.12, and 6.36, and for leaves 1.7, 4.22, and 6.01, respectively. Previous studies by [PERSON] et al. concerning _Carthamus tinctorius_ L. [66] and _Partherium hysterehornts_[25] observed the same correlation between Pb concentration in soil, BCF, and TF.  
The ability of sweet potato to accumulate metals was as follows: Zn > Pb > Cd. With the exception of Cd with BCF < 1, this indicator was >1 for Zn and Pb, from which we can conclude that sweet potato has great potential for use in phytoremediation.