Water content-driven uranium fraction transformation and stability dynamics in contaminated soils

Area of Science:

• Environmental Science
• Geochemistry
• Soil Science

Background:

• Uranium (U) speciation in soils dictates its environmental behavior.
• Soil water content critically influences U speciation and stability, but mechanisms are unclear.

Purpose of the Study:

• Investigate U fraction and stability mechanisms under varying soil water content.
• Elucidate U transformation pathways and influencing factors in contaminated soils.

Main Methods:

• Soil incubation experiments with controlled water content.
• Chemical extraction, stirred-flow experiments, and kinetic modeling.
• Statistical analyses to identify key drivers of U behavior.

Main Results:

• Higher water content (58%) significantly enhanced U stability via reducing microenvironments.
• Microbial reductive dissolution of Fe minerals transformed U species to more stable forms (e.g., organic matter-U).
• Dry-wet cycles suppressed U release by promoting stable U species formation.

Conclusions:

• Reducing conditions and Fe mineral transformations are key to U stabilization.
• Reactive Fe minerals and soil dissolved organic matter (DOM) are critical drivers of U fraction.
• Exchangeable U governs release kinetics, while organic matter-U and carbonate-U dominate stabilization.