Recent research has confirmed that nitrate from fertilizers or animal waste can mobilize naturally occurring uranium from sediment into groundwater. A team of researchers at the University of Nebraska-Lincoln conducted experiments that demonstrated how the presence of nitrate and microbes in sediment can further mobilize uranium, resulting in higher levels of uranium in drinking water. The findings highlight the importance of monitoring nitrate levels in groundwater and maintaining them below the Environmental Protection Agency’s threshold of 10 parts per million to prevent further mobilization of naturally occurring uranium. The research confirms that biochemical events, triggered by microbes, can transform naturally occurring uranium into a form that is easily dissolved in water. The team identified multiple microbial species capable of metabolizing nitrate to nitrite in the sediment samples. The study is the first to establish that the same mobilization process also occurs in natural sediment.
Recent research has confirmed that nitrates from fertilizers or animal waste can transport naturally occurring uranium from underground sediment to groundwater. This new finding builds upon a 2015 study led by Karrie Weber, an associate professor at the University of Nebraska, which found that aquifers with high levels of nitrate contained uranium concentrations far above the threshold set by the Environmental Protection Agency. High levels of uranium in drinking water can cause kidney damage in humans.
Previous research had shown that dissolved inorganic carbon could detach non-radioactive uranium from underground sediment and move it into groundwater. Weber’s team aimed to determine whether nitrate was also contributing to this process. The researchers extracted sediment cores from an aquifer site near Alda, Nebraska, containing natural traces of uranium, and recreated the flow of groundwater to determine if adding nitrate increased the amount of uranium carried away. The experiment confirmed that nitrate indeed facilitated the transport of naturally occurring uranium into groundwater.
This research is particularly relevant for Nebraskans who rely on groundwater for drinking water, including residents of Lincoln and many rural communities. The study’s findings suggest that contamination of groundwater with nitrates from fertilizers or animal waste may result in the presence of high levels of uranium in drinking water.
A recent study conducted by researchers at the University of Nebraska, Lincoln, has found that nitrate from fertilizers or animal waste can mobilize naturally occurring uranium from underground sediment into groundwater. The team’s experiments demonstrated that when simulated groundwater containing nitrate was passed through sediment samples containing uranium, roughly 85% of the uranium was carried away compared to just 55% without nitrate. When nitrate and an inhibitor were added to the water, approximately 60% of the uranium was carried away. The results suggest that the presence of both nitrate and microbes in sediment can further mobilize uranium.
The researchers discovered that microbes living in sediment donate electrons to the nitrate, catalyzing its transformation into nitrite. This nitrite then oxidizes the neighboring uranium, transforming it from a solid mineral into a form that can be dissolved in water. The team identified multiple microbial species capable of metabolizing nitrate to nitrite in the sediment samples.
Although the study confirms the potential for nitrate contamination from fertilizers or animal waste to lead to elevated levels of uranium in groundwater, the team’s previous research suggests that nitrate mobilizes uranium only when it approaches the Environmental Protection Agency’s threshold of 10 parts per million. The study also highlights the importance of monitoring nitrate levels in groundwater and maintaining them below the threshold to prevent further mobilization of naturally occurring uranium.
The researchers’ findings demonstrate that biochemical events, triggered by microbes, can transform naturally occurring uranium into a form that is easily dissolved in water. While this has been previously observed in contaminated areas such as uranium mines or sites of nuclear waste processing, the study is the first to establish that the same mobilization process also occurs in natural sediment.
The article has been re-published from the University of Nebraska-Lincoln’s newsroom website. The materials may have been edited for length and content.
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