Uranium contamination from defunct mines could be a bigger problem than previously thought, according to a study published in Nature Communications. This finding could lead to the revision of uranium mine remediation strategies, which look to remove uranium from contaminated ground and surface waters.

Uranium ore is mined in 20 countries around the world, primarily as a fuel for the generation of nuclear power, and while modern operations are stringently regulated, older, defunct mines have led to uranium contamination of the surrounding environment. Bioremediation attempts to limit contamination of ground and surface waters by converting the mobile uranium (VI) species into the less-mobile uranium (IV) species in constructed wetlands. In order to determine how immobile uranium (IV) really is, Yuheng Wang and colleagues sampled soils beside a stream that passed through a mining-impacted wetland in France, where uranium (IV) concentrations were known to be high. The team’s analyses showed that uranium (IV) was combining with iron and organic matter particles in the soil, which increased its mobility and essentially allowed uranium (IV) to ‘piggy-back’ into the stream.

Constructed wetland systems are a popular means of limiting uranium contamination. These findings indicate that the potential release of uranium (IV) via association with organic matter particles should be considered when designing wetland-based uranium remediation strategies.