Organic Functional Group Chemistry in Mineralized Deposits Containing U(IV) and U(VI) from the Jackpile Mine in New Mexico

Abstract

We investigated the functional group chemistry of natural organic matter (NOM) associated with both U(IV) and U(VI) in solids from mineralized deposits exposed to oxidizing conditions from the Jackpile Mine, Laguna Pueblo, NM. The uranium (U) content in unreacted samples was 0.44-2.6% by weight determined by X-ray fluorescence. In spite of prolonged exposure to ambient oxidizing conditions, ≈49% of U(IV) and ≈51% of U(VI) were identified on U L III edge extended X-ray absorption fine structure spectra. Loss on ignition and thermogravimetric analyses identified from 13% to 44% of NOM in the samples. Carbonyl, phenolic, and carboxylic functional groups in the unreacted samples were identified by fitting of high-resolution X-ray photoelectron spectroscopy (XPS) C 1s and O 1s spectra. Peaks corresponding to phenolic and carbonyl functional groups had intensities higher than those corresponding to carboxylic groups in samples from the supernatant from batch extractions conducted at pH 13, 7, and 2. U(IV) and U(VI) species were detected in the supernatant after batch extractions conducted under oxidizing conditions by fitting of high-resolution XPS U 4f spectra. The outcomes from this study highlight *

Calcium in Carbonate Water Facilitates the Transport of U(VI) in Brassica juncea Roots and Enables Root-to-Shoot Translocation

“…The consequences of uranium (U) contamination in the environment caused by the demand for weapon manufacturing and nuclear energy include negative ecological effects, the potential risks of U entry into food chains, and the subsequent human health exposure. − Uranium accumulates in plant roots, crosses cell structure barriers, and is transported to the shoots. − However, the mechanisms affecting the transport of U in plant root and subsequent root-to-shoot translocation are still largely unknown.…”

Uptake and Toxicity of Respirable Carbon-Rich Uranium-Bearing Particles: Insights into the Role of Particulates in Uranium Toxicity

“…This can be related to the concentrated mass of U in the particles translocated into the cells. These findings are of great importance to semi-arid areas where eolian processes facilitate the frequent transport of U-containing PM at a local and regional scale. ,, In this study, we focused on C-rich U-bearing particles (synthesized as uranyl citrate) as an environmentally relevant model of C-encapsulated U-phases. , This approach facilitated the identification of key components contributing to the toxicity of PM with a complex chemical composition . Future studies should investigate the toxic effects of other metal particulates and chemical phases.…”

“…3,8,9 In this study, we focused on C-rich Ubearing particles (synthesized as uranyl citrate) as an environmentally relevant model of C-encapsulated Uphases. 13,14 This approach facilitated the identification of key components contributing to the toxicity of PM with a complex chemical composition. 60 Future studies should investigate the toxic effects of other metal particulates and chemical phases.…”

“…The cell viability of A549 was assessed using the CellTiter-Blue Cell Viability Assay (Promega Corporation, evaluates the metabolic activity of cells). Dose–response was tested following treatments with C-rich U-bearing particle suspensions or the molar equivalent of soluble U solutions at environmentally relevant concentrations of U (from 0.01 to 445 μM). , The effects of the U particulate form on cell viability were emphasized by comparing C-rich U-bearing particles to organosilica particles containing comparable organic content without U and pure silica particles as an additional control. As a secondary measure of cytotoxicity, cell death was assessed by propidium iodide staining that tests membrane permeability.…”

“…Legacy U mine sites in semi-arid regions are subject to strong eolian processes, which enhance the dispersion and air transport of U-bearing mineral dust, causing concern for toxicological effects on health . Recent studies at the Jackpile Mine located on the Pueblo of Laguna, New Mexico, highlight the role of windblown dust transport in the release of U into the environment. , Fine-grained, U-bearing particulates occur in a variety of mineral associations, including with natural organic matter (NOM). − An important chemical characteristic of the mineralized deposits from the mine sites in New Mexico is the encapsulation of concentrated U by high NOM content [13–44% carbon­(C) by weight]. − To date, the health risks related to suspended PM arising from legacy mine sites are not well defined, and the toxicity of U-bearing particulates remains underestimated.…”