The recent study conducted by Karrie Weber and colleagues at the University of Nebraska-Lincoln experimentally demonstrated that nitrate, a common compound in fertilizers and animal wastes, can contribute to the transport of natural uranium in groundwater.
Research confirms and supports a previous study of Weber dated 2015. In that case it was highlighted that aquifers with high levels of nitrates, such as the one present under Nebraska, also contain concentrations of uranium higher than the threshold established by the American Environmental Protection Agency (EPA). Intake of uranium concentrations above this threshold can cause kidney damage in humans, especially when consumed regularly through drinking water.
Do fertilizers drag uranium underground?
The study just published in Environmental Science & Technology (I link it here) dispelled all doubts. The results demonstrated that nitrate and microorganisms present in the underground sediments contribute to the mobilization of uranium. Nitrate, in particular, triggers a series of biochemical events with subsoil bacteria, eventually making uranium soluble. Summary: Bacteria give electrons to nitrate, turning it into nitrite. The nitrite oxidizes the uranium which ends up being carried into the groundwater.
The experiments
To test their hypotheses, the researchers extracted sediment samples from the Nebraska subsoil and analyzed the effect of adding nitrate on the water. They also identified several microbial species capable of metabolising nitrate into nitrite. It should be emphasized (and Weber herself says it) that nitrate is not a poison: if it exceeds the threshold of 10 parts per million (and some "modern fertilizers" are close to this dosage) they mobilize uranium and damage our health.
The study, published in the journal Environmental Science & Technology (link here), represents an important step forward in understanding the bond between nitrate and uranium in groundwater. Most of all, it strongly emphasizes the importance of keeping nitrate concentrations within safe limits to protect human health.
