# Native Plant Capacity for Gentle Remediation in Heavily Polluted Mines
## 3 Results
### Spatial Ordination  
The principal component analysis (PCA) performed with the all trace-element concentrations of the soils analyzed as a whole clearly separated the contaminated soils from the uncontaminated ones under _D. viscosa_ and _E. pithyusa_ (Figure 4). These contaminated samples had the highest concentrations of Fe, Pb, and Zn with respect to the uncontaminated ones. However, differences among contaminated and uncontaminated soils for _C. salviofilus_ samples were less evident, with high Mn concentrations and low Cu concentrations, than in soils under the other two plant species. The PCA ordination diagram drawn with the concentrations of trace elements in leaves for the three species (Figure 5) reflects again a clear spatial separation between the leaf trace-element samples of _D. viscosa_ and _E. pithyusa_, while this difference was far less noticeable in the case of _C. salviofilus_, signifying that the amount of metals in leaves was similar in both cases, although plants growing on contaminated soils displayed slightly higher amounts. _D. viscosa_ accumulated the highest quantities of leaf Pb and Mn in contaminated soils, followed of Zn and Cu, while _E. pithyusa_ accumulated more leaf Zn under contaminated soils, and more Fe and Cu in the uncontaminated ones. Figure 3: Translocation factor for leaves and roots of C. salviofilus, D. viscosa, and E. pithyusa in contaminated soil (C) and uncontaminated soil (NC). The mean and standard error bars of the mean are indicated. The non-parametric Kruskal-Wallis test was applied. Different letters indicate significant differences at a significance level <0.05 for the same plant growing on contaminated and uncontaminated soil. The PCA performed with the concentrations of trace elements in roots for the three plant species (Figure 6) did not show a clear separation between _C. salviofilus_ in contaminated and uncontaminated soils. In general, samples of _E. pithyusa_ and _D. viscosa_ under contaminated and uncontaminated soil were separated although to a lesser extent than for the foliar trace elements. In contaminated soils, _D. viscosa_ was the highest root accumulator of Fe, Pb, Mn, and Zn, while _E. pithyusa_ accumulated the most Cu. These two species growing in uncontaminated soil registered low metal accumulation in the roots while _E. pithyusa_ had the lowest root concentration of Pb. Figure 4: **Principal Components Analysis** (PCA) ordination diagram showing soil samples (points) spatially arranged according to the trace-element concentrations (arrows). CC= contaminated soil under _C. salviofilus_, CN= uncontaminated soil under _C. salviofilus_, DC= contaminated soil under _D. viscosa_, DN= uncontaminated soil under _D. viscosa_, EC= contaminated soil under _E. pithyusa_, EN= uncontaminated soil under _E. pithyusa_. Figure 5: PCA ordination diagram showing the spatial arrangement of samples (points) with regard to the foliar concentrations in trace elements (arrows), plant species, and soil (contaminated or uncontaminated). CC= contaminated soil under _C. salviofilus_, CN= uncontaminated soil under _C. salviofilus_, DC= contaminated soil under _D. viscosa_, DN= uncontaminated soil under _E. pithyusa_. According to the redundancy analysis (RDA) diagram performed for the trace-element concentration in leaves and in soil (Figure 7), Zn in the soil was the only element that significantly explained the variability in leaf concentrations (_Lambda_\(A\) = 0.33; \(F\) = 7.81; \(P\) = 0.004). In general, no relationship was found between the soil concentrations and leaf concentrations, taking into account all the samples and plant species as a whole. A negative correlation was established between the Mn concentration in the soil and the concentration of Fe, but the correlation was weaker for Cu in leaves. Zn in leaves appeared to be related to some extent to Cu in soil and somewhat less to Fe.