## 4 Discussion
Fe (5,33%) and S (1.48%) are present in average quantities, while heavy metals, rare ones, and Al\({}_{2}\)O\({}_{3}\) are in low quantities (under 1%). All other compounds are weakly represented or appear only as traces. However, chemical analyses on the tailings from mines where Au, As, Bi, and Fe were extracted using other technologies revealed that soils were seriously contaminated with several heavy metals and As [46]. The analysis of the chemical composition of technogenic waters in the tailing dumps has shown that these waters contain a lot of trace elements with many of them exceeding themaximum permissible concentrations: total Fe (up to 1908 mg/L), Mn (up to 364.7 mg/L), Al (up to 54.3 mg/L), Zn (up to 71 mg/L), and Pb (up to 0.1). The content of total organic carbon is small (1.3-7.27 mg/L) while the concentrations of rare-earth elements are quite high [47]. Even though the quantities determined in water cannot be compared with the ones determined in the soil from the present article, we can see a similar ordering regarding the concentration of the above-mentioned elements. The controlling and successful prevention of wastewater from these areas containing cooper is important for the safety and health of plants, animals, and people and for the conservation of ecological environments [48]. Even if vegetation has a special capacity to reduce the amount of heavy metals in the soil, the wastewater from the preparation of ones can be treated using new technologies, such as the use of selective absorption materials. [49]  
The average chemical composition of IOparite tailing dump exploitation shows a weight percentage composition as follows: SiO\({}_{2}\)--48.255; TiO\({}_{2}\)--0.975; Al\({}_{2}\)O\({}_{3}\)--23.085; Fe\({}_{2}\)O\({}_{3}\)--5.105; FeO--0.59; MnO--0.215; CaO--1.48; MgO--0.43; K\({}_{2}\)O--4.345; Na\({}_{2}\)O--13.475; P\({}_{2}\)O\({}_{5}\)--0.665; SrO--0.285; and F--0.0745; SO\({}_{3}\)--0.075 [50]. In the case of the waste heaps from Moldova Noua, the initial percentage concentrations of some elements are similar: SiO\({}_{2}\)--31.82; Fe--5.33; S--1.48; Mn--0.059 (in the aforested waste heap); Mg--1.165 (in the aforested waste heap); and CaO--15; K--0.02396 (in the aforested waste heap). Carbonates have also been identified as a sink of metals [51]. Soil's Chemical Composition in Forest Plantations from Waste Heaps and the Influence of Forest Vegetation on These Variations  
The variation of the chemical composition for some elements from the waste heap's technosoil is highly and very highly reversely correlated with the stand's dimensional characteristics such as height (\(r=-0.67\) for Fe; \(r=-0.84\) for Zn; and \(r=-0.72\) for Cd), diameter (\(r=-0.68\) for Zn), and volume (\(r=-0.62\) for Mg). As such, the stand's structural diversity and characteristics play an important role in improving the content of heavy metals in the soil. These characteristics are especially dependent on age, an aspect that was emphasized by other investigations regarding the fertility of technosois. Such studies show that stand-age-dependent forest attributes have a significant positive relationship with total exchangeable bases, litter stock, and community composition, being the best predictors for explaining an increase in fertility for technosoil [52]. The bioaccumulation factor of Cu has a positive correlation with the most mobile fractions of Cu in soils, and once absorbed is immediately translocated to leaves [53]. This high Cu bioaccumulation capacity can lead to a high reversed correlation between Cu soil content and tree height, as we obtained (\(r=-0.66\)). The contact of tree roots with tailings, in aforested areas with topsoil, resulted in high concentrations of Cu in the roots, even if the roots did not penetrate the tailings layer after two growing seasons [54]. In the case of the present study, the roots are deeply in the tailing, taking into account tree height and age.