Russian Academy of Sciences Reveals Mechanism of Microbial Bioremediation Reducing Actinide Content in Groundwater

September 1, 2026 news: Researchers from the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences, in collaboration with the Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences and other institutions, studied the biogeochemical mechanisms affecting the distribution of actinides such as uranium, plutonium, and neptunium during bioremediation of nitrate-contaminated groundwater.

Radionuclide-contaminated groundwater is a significant environmental issue in areas associated with nuclear fuel cycle facilities. Long-lived actinides such as uranium, plutonium, and neptunium, once released into the environment, can migrate over considerable distances with groundwater. Bioremediation, which alters geochemical conditions by stimulating natural microbial processes in the subsurface environment, is considered a potential approach for remediating contaminated zones.

The research team selected groundwater from a waste disposal site near the Siberian Chemical Combine as the study object. Bioremediation of nitrate-contaminated groundwater had previously been conducted in this area. Researchers collected samples immediately after remediation completion, one year after, and two years after, determined the speciation of actinides in groundwater, and assessed their stability through modeling.

The results showed that after bioremediation, the concentration of dissolved uranium in groundwater decreased by more than 10-fold, and plutonium content dropped below the detection limit. Analysis of samples collected one and two years later indicated that despite changes in nitrate concentrations and redox conditions, uranium and plutonium did not exhibit significant redissolution.

Analysis of uranium distribution among fractions of varying dispersity revealed that uranium progressively shifted from predominantly dissolved and nanoscale forms to larger particulate forms associated with clay and iron-bearing components. Thermodynamic modeling results indicated that the formation and stability of sparingly soluble actinide phases such as uraninite, as well as iron-bearing minerals including ferrihydrite, goethite, siderite, and sulfide phases, were maintained.

Ivan Myasnikov, Senior Researcher at the Environmental Radiochemistry Laboratory of the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences and Doctor of Chemistry, stated that microbial transformations in the subsurface environment not only reduced the content of dissolved actinides but also facilitated their redistribution into less mobile dispersed and mineral phases.