## 3 Results
### Discussion  
Table 10 presents a compact summary of the evidence regarding uranium transport in sediments as provided by these experimental simulations. The equilibrium concentration of uranium in the ideal adsorption of uranyl by fine sediments experiment (Section 3.2.1) for solutions with concentrations ranging from 30 to 120 mgU kg\({}^{-1}\), at a pH close to that of oxidized rainwater was found to be significantly high, reaching 44.8 mgU/g sediment. This experiment revealed that clays were primarily responsible for the adsorption of uranyl nitrate. These values contrast those reported by [68], who observed equilibrium adsorptions of 27.4 mgU/g for bentonite and 18.68 mgU/g for kaolinite. The present study analyzed equilibrium over a substantially longer duration than that reported in [68]. The equilibrium value of 44.8 mgU/g sediment establishes an upper limit for the adsorption capacity of the uranyl ion by sediments in the study area, assuming the mineral dissolves in the mineralized zones of Pena Blanca. Furthermore, it indicates that uranyl ions tend to precipitate under neutral to alkaline conditions (Figure 6). The concentration of a mud sample collected from the alluvial fan of the Boca La Colorado stream [34] was 141 mgU kg\({}^{-1}\) of sediment. This concentration represents the highest value reported in the area at sites far from mineral sources. This value is rare in sediments. Ref. [69] have reported 100-200 mgU kg\({}^{-1}\) in sediments from two lakes in the Murmansk region, Arctic. Those high U concentration values have been explained by uranium migration from underground mineralized zones associated with Mo and REE. In that work, these concentrations are found in sediments with evidence of bio-reduction by organic matter. High concentration values of uranium have been observed in the surroundings of milling tailings from abandoned mines (e.g., [70]). The simulation of uranyl ion adsorption by sediments from the characteristic profile of SPB (Section 3.2.2) corresponds to a scenario analogous to uranium dissolution by surface \begin{table}
\begin{tabular}{c c c} \hline
**Experiment** & **U Conc. (mg kg\({}^{-1}\))** & **Distinctiveness, Singularity, Evidence** \\ \hline Batch & \(44.8\times 10^{3}\) & Upper limit \\ Mud \({}^{-}\)M2\({}^{-}\) & 141 & Maximum value at the study site \({}^{-}\) \\ UNC6\({}^{-}\) & 127 & Initial transport and adsorption in CSC \\ UN6C\({}_{2}\) & 27 & Initial transport and adsorption in FSC \\ UN12C\({}_{1}\) & 303 & Maximum value of adsorption in CSC \\ UN12C\({}_{2}\) & 174 & Maximum value of adsorption in FSC \\ \hline \multicolumn{3}{c}{Tomography} \\ \hline URP6C\({}_{1}\) & 110 & Mineral particles close to the horizon. Dispersion up to 55 mm \\ URP6C\({}_{2}\) & 103 & Mineral particles close to the horizon. Dispersion up to 55 mm \\ URP12C\({}_{1}\) & 37 & \\ URP12C\({}_{2}\) & 14 & Mineral particles are dispersed by liquid flow. Dispersion up to 110 mm \\ \hline \end{tabular} \({}^{a}\)[34].  
\end{table} 
Table 10: U Concentration in Clays C\({}_{1}\) and C\({}_{2}\) from UN and URP Experiments. water near mineral sources. In this experiment, the columns were fed with a solution at 569 mgU L\({}^{-1}\), significantly higher than the concentrations reported for the study site. Recent evaluations of natural uranium concentrations indicate values of 0.033 Bq L\({}^{-1}\) in runoff water and 0.122 Bq L\({}^{-1}\) in spring water, respectively [71]. The experiment results demonstrated that the clay fractions \(C_{1}\) and \(C_{2}\) in the UN6 CSC, UN6 FSC, UN12 CSC, and UN12 FSC segments exhibit a greater capacity to retain uranium than the silt fractions. This enhanced adsorption capacity of clays has also been observed in studies of uranium-contaminated sediments, where saturation values in the adsorption isotherms are higher for finer fractions, correlating with their larger surface areas of interaction [72]. Transport modeling in URP columns (Section 3.2.3) revealed low uranium concentrations in the effluent solutions.