## 3 Results and Discussion
### Transfer Factors of \({}^{238}\)U and \({}^{226}\)Ra between Soil and Studied Plants
Finally, the incorporation of \({}^{238}\)U and \({}^{226}\)Ra did not show any correlation with each other, as the angle of these two variables is practically 90\({}^{\circ}\). This effect is consistent with the TFs obtained for these two elements (Figure 4). The results obtained show that both _Scolymus Hispanicus_ L. and _Eryngium Campestre_ L. are the plants that absorb the most \({}^{238}\)U and \({}^{226}\)Ra, along with other heavy metals such as Fe and Al. _Scolymus Hispanicus_ L. has the ability to alter the soil as its roots generate organic acids and sugars that lead to an increase in pH, the formation of chelates with heavy metals, and an increase in the presence of microorganisms [24]. _Eryngium Campestre_ L. exhibits a high level of mycorrhizal in its roots, which also promotes the greater mobility of \({}^{238}\)U and \({}^{226}\)Ra, as well as heavy metals, enhancing their incorporation into the plant [25]. Although future research is necessary to validate these hypotheses, the correlation with sulfur present  
Figure 6: The transfer factors for \({}^{226}\)Ra and \({}^{238}\)U for the four plant species studied. in the composition of minerals found in a copper tailings site (see Section 3.1.) indicate the possible decomposition of the sulfides present. Therefore, these two plants could be candidates for use in phytoremediation. General Model of Transfer of \({}^{238}\)U and \({}^{226}\)Ra Based on the Transfer of Stable Elements  
The transfer models of \({}^{238}\)U and \({}^{226}\)Ra obtained through multiple linear regression analysis have the following equations:  
\[TF_{238_{U}}=(1.84\pm 0.49)\cdot TF_{Al}+(0.00024\pm 0.0001)\cdot TF_{S}-(0.00 066\pm 0.00069) \tag{3}\]  
\[TF_{226_{Ra}}=(10.0\pm 4.6)\cdot TF_{Al}+(0.0036\pm 0.0014)\cdot TF_{Ca}-(4.2 \pm 2.0)\cdot TF_{Fe}+(0.016\pm 0.010)\cdot TF_{Mg}-\cdots\] \[\cdot\cdots-(0.62\pm 0.30)\cdot TF_{Na}+(1.72\pm 0.84)\cdot TF_{Ti}+(0.0032\pm 0.0074) \tag{4}\]  
The residuals obtained through the proposed models for \({}^{238}\)U and \({}^{226}\)Ra were evaluated using RSE and RMSE statistics, yielding \(1.5\cdot 10^{-4}\) and \(1.5\cdot 10^{-4}\) for \({}^{238}\)U and \(8.8\cdot 10^{-3}\) and \(7.4\cdot 10^{-3}\) for \({}^{226}\)Ra. Therefore, the values estimated by the models yield consistent results. The models were simplified by eliminating the parameters with a \(p\)-value greater than 0.05 in the analysis of variance. The weight of the most influential factors in the absorption of \({}^{238}\)U and \({}^{226}\)Ra was determined by examining the standard coefficients of the fit. The parameter that had the greatest weight in the fit for \({}^{238}\)U was Al, while for \({}^{226}\)Ra, it was Al >> Fe > Ti. The interaction observed between \({}^{238}\)U and Al may be equivalent to that found by [PERSON] and [PERSON] [60], who observed an interaction between Al and UO\({}_{2}\)\({}^{2+}\) in clay samples due to available sites on the surface where Al was present. This same effect was found by [PERSON] et al. in clays [61]. Although the interactions between \({}^{238}\)UO\({}_{2}\)\({}^{2+}\) and \({}^{226}\)Ra\({}^{2+}\) with Al\({}^{3+}\) were found in the clay samples, they are extrapolable to soils due to their similar behaviors. Therefore, the absorption of \({}^{238}\)U and \({}^{226}\)Ra is related to that of Al and is directly proportional since the sign found in the model is positive. A relationship between \({}^{226}\)Ra and Fe and Ti has been found in previous studies on granite samples [61]. The interaction of Ti with \({}^{226}\)Ra, according to our results, is positive, which is equivalent to the results obtained by [PERSON] and [PERSON] [58].