# Removal of Heavy Metal Cd Element from Paddy Soil by Geo-Electrochemical Technology
## 5 Conclusions  
1. The experiment findings were that the GT was effective in removing the Cd element from paddy soil, particularly when it was applied directly to the soil. Therefore, it is suggested that in situ treatment of Cd-contaminated paddy fields should be carried out by the GT during the rice fallow period so as to ensure the safe use of the paddy fields.
2. The GT effectively reduced the Cd element content in various parts of the rice plants by reducing the accumulation of Cd in soil by various tissues and organs such as rice roots, stems, leaves, and grains. Furthermore, the implementation of the GT affected the process of the rice plants to transport Cd from the underground parts to the aboveground parts; specifically, it affected the process of the rice root system to transport Cd, thereby ensuring the safe production of the rice.
3. The results showed a good application prospect for the GT to reduce the content of the Cd element in the paddy soil. At the same time, the GT is also expected to show a certain potential in the remediation and treatment of composite-contaminated soils with multiple heavy metal elements.  
Conceptualization, Y.S. and M.W.; methodology, Y.S., M.W. and P.L.; investigation, Y.S., M.W. and Y.J.; data curation, Y.S., M.W. and Y.J.; writing--original draft preparation, Y.S. and M.W.; writing--review and editing, Y.S., M.W. and P.L.; visualization, Y.S. and M.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Guangxi Science and Technology Planning Project (Grant No. 2021 JJ)A150037) and the National Natural Science Foundation of China (Grant No. 42163004).  
**Institutional Review Board Statement:** Not applicable.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Element** & **Cr** & **Ni** & **Cu** & **Zn** & **As** & **Hg** & **Pb** \\ \hline Initial value & \(53.59\pm 1.20\) a & \(19.58\pm 0.41\) a & \(31.99\pm 1.31\) a & \(85.60\pm 4.52\) a & \(20.97\pm 1.45\) a & \(0.16\pm 0.01\) a & \(63.25\pm 2.70\) a \\ T1 & \(47.37\pm 0.23\) b & \(18.44\pm 0.26\) b & \(25.35\pm 2.09\) c & \(77.37\pm 2.57\) a & \(17.45\pm 1.44\) a & \(0.16\pm 0.01\) a & \(57.75\pm 3.22\) a \\ T2 & \(45.78\pm 0.85\) bc & \(18.49\pm 0.26\) b & \(29.14\pm 1.13\) ab & \(81.59\pm 1.76\) a & \(20.46\pm 1.70\) a & \(0.14\pm 0.00\) a & \(69.97\pm 2.27\) a \\ T3 & \(44.45\pm 0.71\) c & \(18.32\pm 0.29\) b & \(27.72\pm 0.37\) bc & \(79.86\pm 1.46\) a & \(20.44\pm 0.38\) a & \(0.15\pm 0.00\) a & \(61.03\pm 2.52\) a \\ Legal limit & \(250\) & \(70\) & \(50\) & \(200\) & \(30\) & \(0.5\) & \(100\) \\ \hline \end{tabular} Note: Units are mg/kg. The results are displayed as mean \(\pm\) standard deviation. Different letters after the value indicate significant differences (\(p<0.05\)). The legal limits are derived from Chinese national standards (GB 15618-2018).  
\end{table}
Table 3: The content of the remaining seven heavy metal elements of paddy soil in the Agricultural Science Institute experiment site.  
Figure 6: Variation in Cd translocation factor in various tissues and organs of rice. The T3 group was the control group, and the T2 group used the geo-electrochemical technology. Different letters above the error lines indicate significant differences (\(p<0.05\)).