Title: Effect of Calcium on the Bioavailability of Dissolved Uranium(VI) in Plant Roots under Circumneutral pH.
Authors: El Hayek, Eliane; Torres, Chris; Rodriguez-Freire, Lucia; Blake, Johanna M; De Vore, Cherie L; Brearley, Adrian J; Spilde, Michael N; Cabaniss, Stephen; Ali, Abdul-Mehdi S; Cerrato, José M
Published In Environ Sci Technol, (2018 11 20)
Abstract: We integrated field measurements, hydroponic experiments, microscopy, and spectroscopy to investigate the effect of Ca(II) on dissolved U(VI) uptake by plants in 1 mM HCO3- solutions at circumneutral pH. The accumulation of U in plants (3.1-21.3 mg kg-1) from the stream bank of the Rio Paguate, Jackpile Mine, New Mexico served as a motivation for this study. Brassica juncea was the model plant used for the laboratory experiments conducted over a range of U (30-700 μg L-1) and Ca (0-240 mg L-1) concentrations. The initial U uptake followed pseudo-second-order kinetics. The initial U uptake rate ( V0) ranged from 4.4 to 62 μg g-1 h-1 in experiments with no added Ca and from 0.73 to 2.07 μg g-1 h-1 in experiments with 12 mg L-1 Ca. No measurable U uptake over time was detected for experiments with 240 mg L-1 Ca. Ternary Ca-U-CO3 complexes may affect the decrease in U bioavailability observed in this study. Elemental X-ray mapping using scanning transmission electron microscopy-energy-dispersive spectrometry detected U-P-bearing precipitates within root cell walls in water free of Ca. These results suggest that root interactions with Ca and carbonate in solution affect the bioavailability of U in plants. This study contributes relevant information to applications related to U transport and remediation of contaminated sites.
PubMed ID: 30412391
MeSH Terms: Biological Availability; Calcium; Hydrogen-Ion Concentration; New Mexico; Plant Roots; Uranium*