Faculty Advisor: Peter Burns
Winter 2020-21 Project: Breakdown of Uranyl Peroxide Nanoclusters in Low Aqueous Concentrations; Pueblo of Laguna
This proposal includes two research projects. In the first project, I will study the breakdown of uranyl peroxide nanoclusters, specifically determining how changing pH and concentration affects the stability of the nanoclusters. These nanoclusters have been tentatively identified in nuclear waste, and their solubility in water makes them able to flow into water sources, such as a river or stream, contaminating the water supply with uranium. Compared to other elements on the periodic table, actinides have not undergone extensive study. Understanding the breakdown of uranyl peroxide nanoclusters will not only add to our understanding of an understudied group of elements, it will also help us learn the implications of the solubility of nanoclusters and how we can minimize spread of nuclear waste into the environment. In previous experiments, it was found that at low aqueous concentrations and acidic to circum-neutral pHs, the U60 nanocluster dissociates into studtite, a mineral. Since the clusters are initially synthesized by starting with studtite, this signifies that there is a reversible reaction between the nanoclusters and studtite. Speciation occurred at pH levels of 8, 10, and 11. By further probing the cluster under these conditions, specifically by varying the pH levels and concentrations, the formation mechanisms can be determined.
The second research project will involve rock samples from a uranium mine in the Pueblo of Laguna land, a tribe of Native American Pueblo people in New Mexico. Specifically, we will try to determine why the river across from the mine has high concentrations of total dissolved uranium. Uranium mining took place in the Pueblo from 1952-1982, and water samples from the Rio Paguate across from the mining operation show concentrations above 700 ppb of total dissolved uranium, when the maximum level deemed safe by the federal government is 30 ppb of uranium. By investigating and discovering why the concentration of uranium in the Rio Paguate is so high, we can then find a solution and lower the uranium concentration to a safe level. Rock samples were initially collected from the uranium mine, and quartz, uranyl minerals, and natural organic matter (NOM) was found on the samples. The organic material was extracted and put through a gas chromatography–mass spectrometer (GCMS), which showed what the identity of some of the organic matter is. Acetic acid was one organic detected, which at pHs above 5 will deprotonate and act as an anion increasing the solubility of the uranium minerals. The effects of precipitation on the level of uranium concentration in the river will be further explored with the rock samples. The breakdown of organic matter and its deprotonation from the surface of rocks via rainfall may be what causes the uranium concentrations in the river to be so high. Simulating rainfall and determining the organics that come off the rocks through this project will help confirm this, allowing greater insight into the source of uranium in the Rio Paguate.