NP(V) Reduction by Soils: First Confirmation of an Underpredicted Interaction Mechanism

Abstract

Neptunium is a toxic component of radioactive waste whose migration in the environment must be illuminated. The interaction of Np(V) with a peaty-podzolic-gleyic soil profile comprising six horizons was extensively studied. Differences in the shape of the sorption dependencies indicate different mechanisms for the reactions occurring. X-ray absorption spectroscopy provided detailed insights into this interaction, identifying the reduction of Np(V) to Np(VI) in the upper horizons owing to soil organic matter. These findings were compared with sequential extraction results and analyses of soil organic matter dissolution. This comprehensive approach enabled the development of a neptunium interaction scheme across all soil horizons, including previously unaccounted interaction mechanisms.

Keywords: Neptunium, sorption, soil, horizon, reduction