It’s completely natural: using environmental microbes to remove uranium from groundwater
Contamination of soils and groundwater with uranium in the United States poses a significant health risk and will require multiple remediation approaches.
Strategies for remediation of uranium contaminated sites have been researched for decades due to the ancient production of nuclear material in the United States. The United States Environmental Protection Agency (EPA) has set the drinking water standard for uranium at 0.03 parts per million (ppm). Yet most bioremediation studies are seldom conducted at such low uranium concentrations.
It has been almost 30 years since the discovery that microbial phosphatase activity and organic phosphate substrates could be used as a strategy to reduce uranium transport by precipitating uranium phosphate minerals. A wide range of microbial species have been found to aid this process in laboratory and field studies. However, these studies were all conducted at uranium concentrations greater than 5 ppm and do not represent many contaminating environments with low uranium concentrations (less than 0.5 ppm) and pH (pH less than 5 ) where mineralization is difficult.
In a new study by scientists at Lawrence Livermore National Laboratory (LLNL), the team has shown that uranium phosphate minerals do not form abiotically in solution when concentrations are below 0.25 ppm and that the pH is below 5, unlike previous studies conducted at higher concentrations. concentrations. Instead, they found that bacteria in soils and sediments can facilitate the precipitation of uranium phosphate minerals that do not precipitate abiotically.
“Bacterial surfaces can facilitate precipitation of uranium phosphate minerals under these conditions by providing a local environment that is supersaturated with uranium phosphate minerals, leading to heterogeneous nucleation and mineralization,” said Keith Morrison , LLNL scientist, lead author of the study. research appearing in Environmental Science and Technology. “This microbial-mediated process can reduce uranium concentrations below the EPA drinking water limit. These results should be valuable in guiding future uranium and phosphate microbial remediation strategies, where efforts are focused on uranium concentrations and pH ranges more relevant to the environment. “
Other Livermore scientists involved in the study include Mavrik Zavarin, Annie Kersting, James Begg, Harris Mason, Enrica Balboni, and Yongqin Jiao. The work was funded by the Department of Energy’s Office of Science, in part through a grant from the Office of Science’s Early Career Research Program.