Effect of Calcium on the Bioavailability of Dissolved Uranium(VI) in Plant Roots under Circumneutral pH

作者：Eliane El Hayek, Chris Torres, Lucía Rodríguez-Freire, Johanna M. Blake, Cherie L. De Vore, Adrian J. BREARLEY, M. Spilde, Stephen E. Cabaniss, Abdul-Mehdi S. Ali, José M. Cerrato · 发表于：Environmental Science & Technology · 年份：2018 · DOI：10.1021/acs.est.8b02724 · 被引用次数：52 · 研究领域：Radioactive element chemistry and processing、Radioactivity and Radon Measurements、Coal and Its By-products

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 HCO 3 – 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 ( V 0 ) 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–CO 3 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.