# Native Plant Capacity for Gentle Remediation in Heavily Polluted Mines
## 4 Discussion
Some authors [44; 46] have pointed out that the Zn concentration in the root is usually higher than in the aerial part of the plants, especially in soils with high concentrations of this element. However, our analyses indicated less Zn in roots than in leaves (Tables 2 and 3; Figures 5 and 6), especially in _D. viscosa_ and _E. pithyusa_ from contaminated soils. This coincides with findings by other authors who have worked at sites close to the study area [3; 28] and have indicated high Zn concentrations in leaves. The translocation factor for Zn was greater than 1 for all the samples studied except for _C. salviofilus_ collected in uncontaminated soils (Figure 3) and with values greater than 10 for _D. viscosa_ in all the soils studied. These values are higher than those found by [28], but the concentrations in soils and plants indicated by these authors were also lower. The translocation factor was also greater than 1 in _D. viscosa_ for the rest of the elements studied, except for Pb in uncontaminated soils. As Pb is hardly mobile in plant tissues and has a tendency to accumulate in the roots, Reference [47] reported that only 3% of the Pb in the roots is transported to the leaves. However, Cu, being an essential element for plants, can be immediately absorbed by the roots and redistributed and forms a component of key enzymes in physiological processes [44]. In fact, our results showed Cu to be one of the elements with the highest translocation factors, especially in _C. salviofilus_ and _D. viscosa_. The high translocation factors observed in these species make them especially suitable for uses related to the extraction of assimilable elements, since the aerial biomass is easier to eliminate than the roots. On the other hand, the redistribution of trace elements through the plant tissues increases the possibility of their accumulation and stabilization, increasing their value for use in gentle remediation projects. The Zn pool calculated for _D. viscosa_ reached high values (Table 4). Given the biomass developed by the plant, the total amounts of the other elements studied were also noteworthy. This supports that _D. viscosa_ has suitable traits to be used as a phytoextractor. Although it failed to reach values of BCFl\(>1\), it did have other characteristics that should be taken into account, such as a high TF for Pb, Cu, and Mn, together with a large biomass that favors a considerable total extraction of trace elements. Moreover, _D. viscosa_ has the ability to adapt to these contaminated areas, as pointed out by other authors [17]. This large biomass makes _D. viscosa_ a good candidate for use in gentle remediation, as plant species from contaminated media frequently have a small biomass since they use more energy in the mechanisms necessary to adapt to the high concentrations of metals in their tissues [44]. In this sense, the effectiveness of phytoremediation depends on multiple factors including soil characteristics and depth [24], degree of contamination, and trace elements involved, as well as on the plant species with large aboveground biomass capable of bioaccumulating metals and vigorously transferring them from roots to the aerial part [6; 48]. The management of contaminated soil is one of the environmental priorities and challenges worldwide including Europe [16]. Phytoremediation has been questioned due to the difficulties for its efficiency of use at an industrial level, even if the accumulated metal can be reused (phytomining). In this sense, [PERSON] [49] has pointed out the challenge to the \"phyto\" community is to find a new \"non-phyto\" term that describes the betterment of the stressed environments through biological manipulation, perhaps shifting the focus from clean-up to palliative care.