Thesis: Uranium (U) mining activities potentially release radionuclides into downstream areas, particularly wetlands, which could act as sinks for these substances. However, high U content can also result from natural weathering and erosion of uraniferous rocks, comparable to that originating from mining activities. Considering these two potential sources of U-contamination, this study aims to use various approaches including stable Pb isotopes, elemental analysis, U238-series disequilibrium, and geostatistical methods to highlight the sources, transport of radionuclides and their spatial distribution. In our study, soils, and sediments collected from a wetland downstream of the former U mine site Rophin, in France, exhibited notably high U concentrations of up to 16,000 mg.kg-1 in the surface organic layer. The first part of this research focuses on the soil profiles. Three primary U-ore sources of the radioactive contaminants: i) pitchblende (UO2), ii) torbernite Cu(UO2)2(PO4)2, and iii) parsonsite Pb2(UO2)(PO4)2. The limitations of Pb source tracing are further revealed, resulting from its high natural Pb content in parsonsite. Moreover, (230Th/238U) and (226Ra/230Th) activity ratios suggest the potential mobility of both U and radium (Ra) within the soil profiles. These mobility patterns may be influenced by various factors, including U-ore processing, dissolution during transport, and fluctuations in the water table. In the second part of our research, we present our preliminary findings based on radiometric data collected using portable and in-situ gamma spectrometry. This section addresses the co-contribution of radionuclides, spatial structure analysis through variograms, and the spatial distribution mapping of radionuclides by Kriging.