## 3 Results and Discussion
### Pot Experimets
As in the case of _L. sativa_, the total metal content is higher for _B. oleracea_ grown in the CA soil than for the vegetable grown in NOB soil, reflecting the different metal content of the two soils. The concentration gap is particularly significant in the case of the roots, while it decreases if the aerial part is considered. In particular, Ni, As and Co show unusually higher concentrations in the aerial part of _B. oleracea_ grown in NOB soil. Chromium, copper, lead, barium, cobalt, arsenic, and cadmium are more concentrated in the roots of _B. oleracea_ grown in the polluted soil of CA site and in the absence of the AM for both soils. As regards the aerial part, the use of the amendment causes a decrease in Cr, Ni, and Pb concentration in plants grown in both soils and a decrement in Ba and Co concentration in CA plants. On the contrary, the addition of AM induces an opposite trend of concentration for Cu and As in the aerial part, that is higher in the presence of the amendment both in CA and NOB soils. Zinc, although an essential element for plants, has a behaviour similar to that assumed by most of the potentially toxic elements considered. Figure 3: Comparison of potentially toxic elements’ uptake in the roots (**a**,**b**) and in the aerial part (**c**,**d**) of _Brassica oleraca_ grown in CA and NOB soils. Element concentrations are expressed as mg kg\({}^{-1}\) dry weight. The 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**. As observed for _L. sativa_, the concentration values of Pb and Cd in _B. oleracea_ aerial part (Table S4) are below the limits set by Commission Regulation (EC) No. 1881/2006 of the Official Journal of the European Union [39], whether the improver is used or not. The comparison of bioconcentration and translocation factors of _L. sativa_ and _B. oleracea_ grown in CA soil with or without AM, reported in Figures 4 and 5, and the results of ANOVA and Tukey tests reported in Tables S10-S13 of Supplementary Materials, provide evidence that the absorption of metals from the soil by _L. sativa_ increases in the presence of an amendment for most elements, namely Cd, Co, Cr, Ni, Pb and Zn; on the contrary, a clear trend is not evidenced in the case of _B. oleracea_, since BF decreases or increase according to the considered element. Overall, in the presence of AM, _B. oleracea_ shows a lower absorption than _L. sativa_ for most elements examined. Moreover, comparing the two vegetables, the translocation in the case of _B. oleracea_ occurs to a much lesser extent than _L. sativa_. The translocation of potentially toxic elements from roots to the  
Figure 4: Bioconcentration factors (BF) of _Lactuca sativa_ (**a**) and _Brnssica oleracea_ (**b**) grown in the polluted Ca soil with or without the amendment (AM). Letters above columns refer to the summary of multiple comparisons for pairs obtained with Tukey test. Letter **b** identifies BF values whose means are significantly lower than the ones obtained for the BF values identified by letter **a**. Figure 5: Translocation factors (TF) of _Lactuca sativa_ (**a**) and _Brnssica oleracea_ (**b**) grown in the polluted CA soil with or without the amendment (AM). Letters above columns refer to the summary of multiple comparisons for pairs obtained with Tukey test. Letter **b** identifies TF values whose means are significantly lower than the ones obtained for the TF values identified by letter **a**. aerial part is significantly higher for _L. sativa_ cultivated in the absence of an amendment, whereas no significant variation in TF values for _B. olercea_ were observed, with the exception of As, Cd and Zn.