# The Effects of Plasma-Activated Water on Heavy Metals Accumulation in Water Spinach
## 3 Results and Discussion
### Concentration of Heavy Metals in Water Spinach  
To investigate the effectiveness of plasma treatment for reducing the accumulation of heavy metals in vegetables, the heavy metal concentration in water spinach was analyzed. The Cd concentration of water spinach planted in the control and Cd-added soil group are presented in Table 3. When the water spinach was planted in soil with a Cd contaminant, the Cd accumulated by the water spinach was reduced by either plasma treatment on seeds or by using PAW as the irrigation water, but not by both. The Cd concentration of the water spinach in NTS + PAW, PTS + NTW, and PTS + PAW declined by 17.8%, 22.9%, and 4.5%, respectively, when compared with the group without any treatment, especially PTS + NTW group showed the best outcome on declining Cd accumulation in water spinach. Hence, the plasma treatment may demonstrate positive effects for reducing Cd accumulation in water spinach, which is consistent with the results of [PERSON] et al., who reported that Ar/O\({}_{2}\)- and Ar/Air plasma-treated plants exhibited significantly reduced Cd concentrations in the shoot and root in wheat crop when reducing the expression of Cd transporters (_TaLCT1_ and _TaHMA2_) in the root [24]. Meanwhile, Table 3 depicts the results of water spinach planted in soil with Pb contaminant. The Pb concentration of water spinach in NTS + PAW and PTS + NTW decreased by 0.57% and 1.42%, respectively. Moreover, PTS + PAW treatment on water spinach increased the Pb accumulation in the water spinach by 64.8%. Hence, individual plasma treatment of seeds or water did not demonstrate any obvious positive effects for reducing Pb accumulation in water spinach. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multirow{2}{*}{\(n\)} & \multicolumn{3}{c}{**Cd Concentration**} & \multicolumn{2}{c}{**Pb Concentration**} \\ \cline{3-6}  & & **Control Soil** & **Cd-Added Soil** & **Control Soil** & **Pb-Added Soil** \\ \hline NTS + NTW & 3 & ND\(\sim\)LOQ & 18.18–20.43 & 2.60–3.17 & 2222–2492 \\ NTS + PAW & 3 & \(<\)LOQ & 19.06–19.53 & 2.36–3.77 & 2064–2470 \\ PTS + NTW & 3 & ND\(\sim\)LOQ & 20.93–22.28 & 1.84–2.32 & 2182–2429 \\ PTS + PAW & 3 & ND\(\sim\)LOQ & 21.17–21.92 & 1.77–2.80 & 2086–2448 \\ \hline \hline \end{tabular} Note: The results are represented as min–max value. ND: Not detected; LOQ: Limit of quantification.  
\end{table} 
Table 1: The metal concentrations of control soil, Cd-added soil and Pb-added soil (mg/kg D.W.). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multirow{2}{*}{\(n\)} & \multicolumn{3}{c}{**Total Weight (g) of Water Spinach**} \\ \cline{3-5}  & & **Control Soil** & **Cd-Added Soil** & **Pb-Added Soil** \\ \hline NTS + NTW & 3 & 9.24 & 9.43 & 7.28 \\ NTS + PAW & 3 & 7.72 & 7.40 & 6.38 \\ PTS + NTW & 3 & 9.29 & 6.48 & 7.38 \\ PTS + PAW & 3 & 5.91 & 7.43 & 8.39 \\ \hline \hline \end{tabular} Note: The data shown are the sum values of three repeats.  
\end{table} 
Table 2: The total weight of harvested edible parts of water spinach (in term of fresh weight). From a different perspective, although the concentration of Cd in the Cd-added soil (18.18-20.43 mg/kg D.W.) was approximately 100 times lower than the concentration of Pb in the Pb-added cultivation soil (2064-2492 mg/kg D.W.), the Cd concentration in the water spinach (12.1-15.7 mg/kg D.W.) planted in the Cd-added soil was greater than the Pb concentration in the water spinach (6.94-11.6 mg/kg D.W.) planted in the Pb-added soil. This result was consistent with that of [PERSON] and [PERSON] [25], who reported increasing uptake of Cd, Cu, Mn, and Zn by plants correlating with increasing concentration in soil, while the uptake of Pb was poor. The combined effect of plasma-treated seeds and water may depend on the nature of the seeds [26]. [PERSON] et al. [27] conducted an experiment to compare various plasma conditions with different plasma generators on corn seeds grown in six separated locations in Illinois.