## 3 Results
### Discussion
This finding is consistent with the results reported by [11], where the authors noted that stable uranium concentrations were not attained in leachate solutions from contaminated sediment columns. This phenomenon was attributed to the slow release of uranium-bearing solids or limited accessibility to pore fluids. The concentrations of uranium in the fine sediments of the columns suggest the transport of mineral fragments by the feed solution. The verification of this hypothesis was obtained through tomographic analysis. In the photographs (see Appendix B.3, Figure B9) and tomograms (Figure 7), it was observed that throughout the experiments, there was a displacement of uranophane grains due to the advancing water feed. Concurrently, in the EXAFS experiments (Section XAFS), the spectra from the UN experiment were not of sufficient quality to allow for spectral analysis; however, the EXAFS spectra from the URP experiment corroborate the transport of very fine uranophane particulate material to the lower segment fractions of the sediment columns. The experiment conducted on the URP6 and URP12 columns suggests the transport of uranophane particles, resembling the continuous sequence of \({}^{238}\)U activity concentrations reported in the \"El Tigre\" stream [36]. Similar findings were reported by [14], who, through XAFS and \(\upmu\)-XRF techniques, observed diffusely migrating uranium from horizons of UO\({}_{2}\) particles in hot spots. They suggested that this transport involves a combination of intact UO\({}_{2}\) particles and oxidative alteration of uranium. Additionally, ref. [9] observed the physical dispersion of mineralized particles from landfills and naturally mineralized areas in stream sediments from a uranium mine in arid regions. In contrast, ref. [8] conducted a study in the \"Rio Puerco\" area near Church Rock, New Mexico, which experienced a significant incident when an earthen dam at a former uranium mill collapsed [73]. This study found that, within the uranium mining area, uranium-bearing particles from mining waste disposal sites are not transported far from their source. Instead, more soluble uranium-bearing minerals are subjected to dissolution during torrential desert rains. Finally, future research should focus on developing integrated models considering multiple transport mechanisms, including fragmentation, dissolution, adsorption, and sediment dynamics. These models can simulate the interactions between environmental variables, such as rainfall patterns, temperature fluctuations, and soil characteristics, allowing for more accurate predictions of uranium dispersion across various spatial and temporal scales. Additionally, predictive models can be adapted to investigate the potential impacts of climate change on uranium transport. Changing precipitation patterns and an increased frequency of extreme weather events may alter leaching processes and sediment transport, underscoring the need for models that incorporate climate variables. Moreover, it is essential to create models to assess the risk of uranium dispersion to nearby water sources, agricultural lands, and human health. This information will guide remediation efforts to mitigate uranium contamination and inform land-use planning and regulatory decision-making.