## 3 Results and Discussion
### Pot Experimets
In particular, Ba and Ni adsorption seems to be significantly affected by the addition of AM since the difference between their content in the _L. sativa_ samples grown in soils treated or not is very marked. In fact, the addition of the amendment causes a decrease in the concentration of Ni and Ba in the aerial parts of the plants grown in CA soil. Zinc, similar to the elements mentioned so far, presents a higher total concentration in _L. sativa_ grown in the presence of AM, but in this case the amendment does not cause \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Vegetable Species** & **Soil** & **Amendment (AM)** & **Stem Diameter [mm]** & **Leaves Number** & **Leaf Area [cm\({}^{2}\)]** \\ \hline \multirow{4}{*}{_B. oleraca_} & NOB & No & \(2.2\pm 0.1\) & \(8\pm 1\) & \(24\pm 4\) \\  & & Yes & \(6.3\pm 0.6\) & \(12\pm 1\) & \(112\pm 9\) \\ \cline{2-6}  & & & No & \(1.8\pm 0.2\) & \(6\pm 1\) & \(8\pm 1\) \\ \cline{2-6}  & CA & Yes & \(5\pm 1\) & \(12\pm 2\) & \(50\pm 10\) \\ \hline \multirow{4}{*}{_L. sativa_} & NOB & No & \(7.21\pm 0.9\) & \(16\pm 2\) & \(24\pm 1\) \\  & & Yes & \(14\pm 3\) & \(33\pm 2\) & \(86\pm 3\) \\ \cline{2-6}  & CA & No & \(6.8\pm 0.5\) & \(14\pm 1\) & \(14.1\pm 0.3\) \\ \cline{2-6}  & & Yes & \(10.9\pm 0.1\) & \(31\pm 2\) & \(57\pm 3\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Morphometric parameters relating to _Lactuca sativa_ and _Brassica oleracea_ plants grown for 3 months under the investigated experimental conditions. Figure 1: Plants of _Lactuca sativa_ (top) and _Brassica oleracea_ (bottom) grown under different conditions: (**a**) = NOB soil with AM, (**b**) = NOB soil without AM, (**c**) = CA soil with AM, (**d**) CA soil without AM. a strong reduction in its transfer to the edible part. Therefore, Zn, an essential microelement for plant life and very abundant in the soils considered, is well absorbed by the plant. Copper is also an essential element for vegetable species, but its behavior is different since its uptake in the _L. sativa_ is strongly influenced by the presence of amendment in both soils. Copper amount is always higher in _L. sativa_ cultivated without amendment and this could be due to the different speciation of this element, often added as fungicide to the plants also cultivated in urban gardens, and at the lowest concentration necessary for plant growth. In the case of As and Cd, the total concentration in the vegetable is comparable. The transport of Cd in the aerial parts of the plant is greater for the samples grown without the use of amendment, contrary to what was observed for As, where the addition of amendment does not cause a decreased concentration in the aerial part. Regardless of the improver's use, the concentration values of Pb and Cd in _L. sativa_ (Table S2) are well below the maximum concentration allowed for edible parts of broad-leaved vegetables by Commission Regulation (EC) No. 1881/2006 of the Official Journal of the European Union [41], which defines as a threshold 0.30 mg kg\({}^{-1}\) wet weight for Pb and 0.20 mg kg\({}^{-1}\) wet weight for Cd. In Figure 3, the concentrations of potentially toxic elements analyzed in roots (a, b) and in the aerial part (c, d) of _B. olerca_ grown in the soil of the two sites with or without the addition of the soil  
Figure 2: Comparison of potentially toxic elements’ uptake in the roots (**a**,**b**) and in aerial part (**c**,**d**) of _Lactuca sativa_ grown in CA and NOB soils. Elements concentrations are expressed as mg kg\({}^{-1}\) dry weight. Letters above columns refer to the summary of multiple comparisons for pairs obtained with Tukey test. Letter **b** identifies plant samples whose mean concentrations in the respective elements are significantly lower than the ones obtained for plant samples identified by letter **a**; the same concept applies to letter **c** with respect to letter **b** and letter **d** with respect to letter **c**. amendment are reported, whereas the results of ANOVA and Tukey tests are reported in Tables S8 and S9 of Supplementary Materials.