Uranium (IV) found to be mobile in a natural wetland
PostedDecember 18, 2013
Because they are known to mop up pollutants, artificial wetlands are considered to be an efficient strategy to contain waterborne uranium. But studying a natural wetland near a former uranium-mining site in the French region of Limousin, researchers have found that under certain circumstances, uranium can be partly remobilized into the surrounding water. In a recent publication in Nature Communications, they show how it becomes mobile again by binding to tiny metallic and organic compounds with a little help from ambient bacteria. Their study, carried out in collaboration with the HZDR in Germany, and Areva in France, has been highlighted in a press release by the journal.
In nature, uranium is found in two forms: U-4 and U-6, where the numbers indicate how many chemical bonds the atom can form. “Until recently, scientists thought that U-4 was immobilized as a mineral, while U-6 was considered to be the only highly soluble form,” says the study’s principle investigator Rizlan Bernier-Latmani. Today, scientists know that this distinction is not quite as clear-cut, having discovered a non-soluble, yet highly mobile form of U-4.
In wetlands, bacterial or chemical processes transform the soluble form of uranium, U-6, into U-4. “This was considered beneficial from an environmental point of view, as it was assumed to sequester the contaminant, keeping it out of the water,” explains Bernier-Latmani.