Pollution from uranium, thorium, and radium poses significant environmental and public health risks. This study examines two regions with distinct soil types: carbonated and marshy soils. Soil samples were selected based on carbonate (28.83% and 9.79%) and organic matter content (22.6% and 1.8%). The research aims to evaluate the role of carbonates and organic matter in retaining radioactive elements and to identify which metal (thorium, uranium, or radium) is most retained. The methodology included physicochemical soil analysis and sorption experiments, varying pH and organic carbon (humic acid and biochar). Results show that thorium has the highest adsorption affinity due to the stability of its solid compounds. Uranium and radium exhibited lower retention, with behavior varying by soil type. The study also compared recalcitrant and active organic matter, revealing that both carbonates and organic matter significantly enhance soil depollution. However, acidic organic materials, unlike basic ones, do not improve metal retention. Instead, they promote metal breakdown, increasing bioavailability and plant uptake. These findings suggest that biochar application could effectively remediate soils contaminated with radioactive elements, offering a sustainable agricultural solution. This approach reduces pollution while improving soil health and crop safety.