Effects of Depleted Uranium on Soil Microbial Activity: A Bioassay Approach Using ¹⁴C-labeled Glucose

Abstract

The short and long term influence of depleted uranium (DU) on soil microbial populations remains largely understudied. To understand short term effect of DU on soil microbial activity, an incubation study was conducted using ¹⁴C-labeled glucose. Two soils of contrasting texture (Eurtic cambisol and Haplic podzol) were amended with increasing concentrations (0.5 mmol·L⁻¹ to 10 mmol·L⁻¹) of either potassium nitrate (KNO₃) or DU as uranyl nitrate UO₂(NO₃)₂. Following addition, ¹⁴C-labeled glucose was then added to the soil and ¹⁴CO₂ production from the mineralization of glucose measured at different time intervals (1 h to 14 d) to assess microbial activity. Glucose mineralization by the microbial community showed non-significant effect by different concentrations of DU on both soils. Fitting a double first order kinetic equation revealed that 87%∼92% of the added glucose was retained in the microbial biomass prior to mineralization. However, comparison of the kinetic values for different concentrations of KNO3 and DU also showed non-significant difference in both soils. The results imply that there is no significant deleterious effect of DU on soil microbial activity in the short (<24 h) or longer term (<30 d).