Did you know that nitrate can cause uranium to be released into groundwater?

A new study has confirmed that nitrate, a common compound in fertilizers and animal waste, can transport naturally occurring uranium from underground to groundwater. Researchers have discovered that aquifers contaminated with high levels of nitrate also contain concentrations of uranium that exceed the threshold set by the Environmental Protection Agency, which can cause kidney damage in humans if regularly consumed through drinking water.

To test this hypothesis, the researchers extracted two cylindrical sediment cores from an aquifer site in Nebraska that contains naturally occurring trace amounts of uranium and allows groundwater to flow into the adjacent Platte River. They then recreated the flow in the sediment samples to determine whether adding a little nitrate to the water would increase the amount of uranium carried with it.

The results showed that water containing nitrate carried approximately 85% of the uranium, compared to only 55% when the water lacked nitrate. They also found that a series of biochemical events, initiated by the microbes, was transforming the solid uranium into a form that could easily dissolve in water. The study is the first to establish that the same mobilization process also takes place in natural sediments.