# The Effects of Plasma-Activated Water on Heavy Metals Accumulation in Water Spinach
## 4 Conclusions  
The accumulation of heavy metals by water spinach was found to be dependent on the type of heavy metals and their concentration in soil. A higher concentration of Cd was accumulated in water spinach compared to that of Pb. The PTS + NTW treatment group demonstrated the highest reduction in Cd accumulation in water spinach. However, plasma treatment of seeds or PAW irrigation was able to reduce the accumulation of heavy metals in water spinach, except for water spinach in the group of PTS + PAW grown in Pb-added soils. The limitations of this study, such as the insufficiency of the planting space, the fixed condition of the PAW generator, and the small sample size, could have led to imperfections in the study. An increased sample size in order to achieve a more  
\begin{table}
\begin{tabular}{c c c c} \hline
**Treatment** & \(n\) & **Cd** & **Pb** \\ \hline NTS + NTW & 3 & 0.819 \(\pm\) 0.048 & 0.003 \(\pm\) 0.000 \\ NTS + PAW & 3 & 0.669 \(\pm\) 0.008 & 0.003 \(\pm\) 0.000 \\ PTS + NTW & 3 & 0.564 \(\pm\) 0.019 & 0.003 \(\pm\) 0.000 \\ PTS + PAW & 3 & 0.695 \(\pm\) 0.012 & 0.005 \(\pm\) 0.000 \\ _p_-value & & 0.016 * & 0.092 \\ \hline \end{tabular} Note. * \(p\) < 0.05, Kruskal-Wallis Test. Samples used in the analysis were the mixtures of three pots of plants.  
\end{table}
Table 5: Bioconcentration factors (BCF) of Cd and Pb in water spinach.  
powerful analysis, modification of the optimal parameters (plasma power, treatment time, etc.) of the PAW treatments, and the selection of a more suitable PAW generator will all be taken into account in future studies. Meanwhile, since the heavy metal concentration used in this study was high and the plant growth in the current study was not consistent with that described in some other studies in the literature, this study on the effects of various concentrations of Cd and Pb on the growth and development of water spinach is a prerequisite for research into the combined influence of PAW and heavy metals on this plant species.  
The following are available online at [[https://www.mdpi.com/article/10.3390/app11115304/s1](https://www.mdpi.com/article/10.3390/app11115304/s1)]([https://www.mdpi.com/article/10.3390/app11115304/s1](https://www.mdpi.com/article/10.3390/app11115304/s1)). Table S1 The physiochemical properties of PAW under different treatment time, Figure S1 The pH values of PAW under different treatment time (\(n=3\)), Figure S2 The ORP values of PAW under different treatment time (\(n=3\)), Figure S3 The electrical conductivity of PAW under different treatment time (\(n=3\)), Figure S4 Concentration of H\({}_{2}\)O\({}_{2}\) produced in PAW at different treatment time (\(n=3\)), Figure S5 The average height of water spinach planted in Cd-added soil under different treatments, Figure S6 The average height of water spinach planted in Pb-added soil under different treatments, Figure S7 Bioconcentration factors of Cd and Pb in water spinach.  
Conceptualization, H.-L.C.; methodology and processing, T.-K.K., C.-Y.H., C.-M.L. and H.-L.C.; chemical analysis, T.-K.K.; resources, C.-Y.H., C.-M.L. and H.-L.C.; writing-original draft preparation, T.-K.K. and C.-Y.H.; writing-review and editing, C.-M.L. and H.-L.C.; supervision, C.-Y.H.; project administration, C.-M.L. and H.-L.C.; funding acquisition, H.-L.C. All authors have read and agreed to the published version of the manuscript.  
This work has been supported by Lab of Hsiu-Ling Chen.  
Not applicable.  
This study did not report any data.  
The authors acknowledge that the plasma jet system was designed and developed by the Mechanical and Mechatronics Systems Research Lab, Industrial Technology Research Institute (ITRI) (Hsinchu, Taiwan).  
The authors declare no conflict of interest.