Farm runoff linked to uranium in groundwater

The water flowing from taps across America’s heartland carries a hidden history. Every drop has filtered through layers of sediment, picking up minerals along the way. Now scientists have discovered that agricultural chemicals may be altering what the water carries into homes.

Researchers at the University of Nebraska–Lincoln have uncovered a troubling connection between farm runoff and naturally occurring uranium in aquifers. Their findings reveal how nitrate from fertilizers and animal waste can trigger the release of uranium into groundwater supplies.

The science behind the contamination

The team, led by associate professor Karrie Weber, collected sediment cores from the High Plains Aquifer near Alda, Nebraska. This vast underground reservoir supplies drinking water to millions of people across eight states.

In laboratory experiments, the researchers pumped simulated groundwater through these sediments. The presence of nitrate in the water led to the removal of approximately 85 percent of the uranium. Without nitrate, only about 55 percent moved.

The difference comes down to microbial activity. Bacteria living in the soil transform nitrate into reactive compounds that chemically alter uranium, dissolving it into water that then travels through the aquifer.

“Most Nebraskans do rely on groundwater as drinking water,” said Weber. “So when you have high concentrations, that becomes a potential concern.”

Why this matters for public health

Uranium is toxic to the kidneys when consumed over time. Federal regulations set a maximum contaminant level of 30 micrograms per liter for uranium in drinking water.

Nitrate contamination is already a known concern in agricultural regions. The legal limit for nitrate in public drinking water is 10 milligrams per liter. Previous surveys from the U.S. Geological Survey have documented that uranium hot spots often track with nitrate levels, particularly in shallow groundwater near farmed soils.

A silver lining for communities

The encouraging news is that efforts to reduce nitrate contamination may address both problems simultaneously. Communities already working to limit fertilizer runoff could also be protecting themselves from uranium exposure.

“Nitrate isn’t always a bad thing, but the important thing is not to have too much,” Weber explained.

The complete study was published in Environmental Science & Technology.

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