AUGUST 18, 2015
By JOSH FUNK / The Associated Press
OMAHA, NE
A
new study suggests that nitrates may play a key role in increasing uranium contamination in groundwater.
The researchers from the University of Nebraska-Lincoln estimate that nearly 2 million people in California and the Great Plains live over groundwater that has been contaminated with uranium, which can cause health problems.
The study found that 78 percent of the groundwater samples that showed unsafe levels of uranium were from areas with high levels of nitrates, which typically come from nitrogen fertilizers and animal waste.
"If the problem is this widespread, more research needs to be done," said UNL assistant professor Karrie Weber, who led the research.
Environmental Protection Agency rules say that uranium shouldn't exceed 30 micrograms per liter in drinking water. Weber's research found examples in California wells above that threshold.
Prolonged exposure to high levels of uranium in water has been linked to kidney problems and increased cancer risk.
Some studies have also suggested that uranium might accumulate in certain crops if they are irrigated with contaminated water.
Weber said groundwater samples aren't always tested for uranium, making it harder to study. She said the lack of testing also raises safety concerns because smaller communities and rural families often use well water without treating it.
Weber said the nitrates moving through the soil can convert uranium from a solid state to a soluble form that can contaminate groundwater.
"As nitrates come into the system, they are increasing the concentration of uranium in the water," Weber said.
Data from roughly 275,000 samples from two of the nation's largest aquifers — the High Plains aquifer and the Central Valley aquifer in California — were examined for the study. Those two underground stockpiles supply water for irrigation and many communities rely on the aquifers for drinking water.
The High Plains Aquifer stretches underneath some 174,000 square miles in parts of South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico and Texas.
The study was published in the August edition of the journal Environmental Science and Technology Letters.
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Two major US aquifers contaminated by natural uranium
Naturally occurring uranium is being mobilized by farm-related pollution
Date:August 17, 2015
Source:University of Nebraska-Lincoln
Summary:
Nearly 2 million people throughout the Great Plains and California above aquifer sites contaminated with natural uranium that is mobilized by human-contributed nitrate, according to a new study. Data show that many Americans live less than two-thirds of a mile from wells that often far exceed the uranium guideline set by the Environmental Protection Agency. Share:
The intensity of groundwater contamination via uranium (red) and nitrate (blue) is shown in two major aquifers and other sites through out the nation. UNL researcher Karrie Weber says the availability of uranium data pales compared to that of nitrate.
Credit: University of Nebraska-Lincoln
Nearly 2 million people throughout the Great Plains and California above aquifer sites contaminated with natural uranium that is mobilized by human-contributed nitrate, according to a study from the University of Nebraska-Lincoln.
Data from roughly 275,000 groundwater samples in the High Plains and Central Valley aquifers show that many Americans live less than two-thirds of a mile from wells that often far exceed the uranium guideline set by the Environmental Protection Agency.
The study reports that 78 percent of the uranium-contaminated sites were linked to the presence of nitrate, a common groundwater contaminant that originates mainly from chemical fertilizers and animal waste. Nitrate mobilizes naturally occurring uranium through a series of bacterial and chemical reactions that oxidize the radioactive mineral, making it soluble in groundwater.
UNL researchers Karrie Weber and Jason Nolan found that the High Plains aquifer contains uranium concentrations up to 89 times the EPA standard and nitrate concentrations up to 189 times greater. The uranium and nitrate levels of the California-based Central Valley aquifer measured up to 180 and 34 times their respective EPA thresholds.
The authors published their findings in the August edition of the journal Environmental Science and Technology Letters. Their research was funded in part by the U.S. Geological Survey.
"It needs to be recognized that uranium is a widespread contaminant," said Weber, assistant professor of biological, Earth and atmospheric sciences. "And we are creating this problem by producing a primary contaminant that leads to a secondary one."
Prior research has suggested that prolonged drinking of uranium-contaminated water may lead, or make people more susceptible, to kidney damage and elevated blood pressure. According to Weber, peer-reviewed studies have also indicated that food crops can accumulate uranium when irrigated by water containing high concentrations of it.
The High Plains aquifer -- the largest in the United States -- provides drinking water and irrigation for an eight-state swath that stretches from South Dakota through Nebraska and into northern Texas. As California's largest reservoir, the Central Valley aquifer sits beneath some of the state's most fertile agricultural land. According to a 2012 census from the U.S. Department of Agriculture, the two aquifers irrigate cropland that accounts for one-sixth of the annual revenue generated by U.S. agriculture.
The researchers also determined that only one of the six wells located near a former or current mining site was contaminated. This finding counters the notion that uranium contamination stems primarily from mining operations or spent nuclear fuel, Weber said.
"We hope that this study serves as a catalyst to get other people interested in this issue," she said. "If the problem is this widespread, more research needs to be done. We're limited by the data that's been collected, and uranium isn't often monitored."
Weber said the expense of water treatment plants -- specialized facilities that can cost tens of millions of dollars -- often puts them out of financial reach for smaller and rural communities. Addressing the issue might require managing groundwater and focusing on the aquifers' sediment, which houses bacteria that can help control uranium by breathing and eating it, she said.
Regardless of the approach, Weber said it is important for decision-makers and researchers to account for the presence of uranium in U.S. water sources.
"When you start thinking about how much water is drawn from these aquifers, it's substantial relative to anywhere else in the world," Weber said. "These two aquifers are economically important -- they play a significant role in feeding the nation -- but they're also important for health.
"What's the point of having water if you can't drink it or use it for irrigation?"