Underground uranium can pose a threat to freshwater bodies, especially when it is in a soluble form. To reduce contamination risk, researchers have proposed strategies that aim at immobilizing uranium, by making it less soluble. Several ways of achieving this transformation have been proposed in the past, but due to the difficulty of capturing chemical processes underground, they have not been extensively studied in the field.
Using a combination of laboratory and field experiments, the research team including researchers from the USA and Rizlan Bernier-Latmani’s group at EPFL studied the fate of soluble uranium at a former uranium milling site in Colorado, USA. They identified multiple transformation pathways that involve direct interactions with biological agents such as bacteria as well as indirect interactions that implicate products of biological activity such as iron sulfide minerals.
This work, presented in the Proceedings of the National Academy of Sciences on March 5, 2013, demonstrates the co-existence of multiple transformation pathways that convert soluble uranium into different end products and reconciles both laboratory and field observations that until now appeared to be contradictory.