# Improvement of Arsenic Phytoextraction Using Indigenous Bacteria and Mobilizing Agents
## 3 Results and Discussion
### Mesocosms Tests with 0.2 M Oxalate + 0.01 M Ascorbic Acid  
The average biomass values for aerial and root parts obtained from plants grown in the control soils and in soils treated with the leaching solution (0.2 M potassium acid oxalate and 0.01 M ascorbic acid) in the presence of PGPR are shown in Figure 5.  
The data obtained in the mesocosm tests confirmed what has already been seen in the microcosm tests, namely, that the treatment with the leaching solution does not significantly influence the production of biomass. The data relating to the absorption of As by plants are shown in Table 3. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multicolumn{2}{c}{_Z. mays_} & \multicolumn{2}{c}{_C. sativa_} \\ \cline{2-5}  & **Roots** & **Shoots** & **Roots** & **Shoots** \\ \hline CT & 0.15 \(\pm\) 0.02 a & 0.06 \(\pm\) 0.01 a & 0.07 \(\pm\) 0.01 a & 0.03 \(\pm\) 0.01 a \\ Ox 0.1/AA 0.01 & 3.30 \(\pm\) 0.36 b & 0.90 \(\pm\) 0.07 b & 1.28 \(\pm\) 0.15 b & 1.61 \(\pm\) 0.11 b \\ Ox 0.2/AA 0.01 & 17.70 \(\pm\) 1.86 d & 8.32 \(\pm\) 0.50 d & 8.20 \(\pm\) 0.90 d & 6.35 \(\pm\) 0.44 c \\ Ox 0.2/AA 0.02 & 8.60 \(\pm\) 0.77 c & 3.80 \(\pm\) 0.23 c & 4.60 \(\pm\) 0.46 c & 5.80 \(\pm\) 0.29 c \\ \hline \hline \end{tabular}
\end{table} 
Table 2: As concentrations (mg kg\({}^{-1}\)) in roots and shoots of _Z. mays_ and _C. sativa_ grown on As-contaminated soils treated with different mixtures of oxalate and ascorbic acid (microcosm tests). The values are the means of three replicates and the error bars show \(\pm\) standard deviations. The different letters within the same column represent different significance levels at \(p<\) 0.05 (Tukey’s test). Figure 4: Arsenic uptake by (**a**) roots and (**b**) shoots of _Z. mays_ and _C. sativa_ grown on As-contaminated soils treated with different mixtures of oxalate and ascorbic acid (microcosm tests). The values are the means of three replicates and the error bars show the standard deviations. Values with different letters are significantly different at the 5% probability level (Tukey’s test). On the basis of the results obtained, it was confirmed that the addition of the oxalate + ascorbic acid leaching solution is able to increase the bioavailability of arsenic, thus allowing its absorption by plants. In particular, corn appears to have a greater absorption capacity than hemp. However, in a field application, an important role is played by the biomass produced, which has a decisive impact on total removal. The total arsenic removal values during the mesocosm tests shown in Figure 6 confirm the efficacy of treatment with the mobilizing agents. In quantitative terms, the amount of As removed was not particularly high (a few micrograms adsorbed per plant), but it is necessary to take into account the reduced growth of plants in the mesocosms. Therefore, it is safe to assume that the uptake will increase in field tests, where plants will be able to develop more. Figure 5: Dry weights (mg pot\({}^{-1}\)) of (**a**) roots and (**b**) shoots of \(Z\). _mays_ and _C. sativa_ grown on soil control (CT) and soils treated with the 0.2 M oxalate and 0.01 M ascorbic acid solution (mesocosm tests). Values are the means of three replicates and the error bars show the standard deviations. Values with different letters are significantly different at the 5% probability level (Tukey’s test). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multicolumn{2}{c}{_Z. _mays_} & \multicolumn{2}{c}{_C. sativa_} \\ \cline{2-5}  & **Root** & **Shoot** & **Root** & **Shoot** \\ \hline CT & 2.48 \(\pm\) 0.30 a & 1.23 \(\pm\) 0.10 a & 2.15 \(\pm\) 0.26 a & 1.05 \(\pm\) 0.08 a \\ Ox 0.2/AA 0.01 & 15.8 \(\pm\) 1.42 b & 10.41 \(\pm\) 0.52 b & 10.1 \(\pm\) 1.06 b & 8.12 \(\pm\) 0.49 b \\ \hline \hline \end{tabular}
\end{table} 
Table 3: As concentrations (mg kg\({}^{-1}\)) in roots and shoots of \(Z\). _mays_ and _C.