Chris Torres Lucia Rodriguez-Freire Johanna M. Blake Cherie L. De Vore Adrian J. Brearley Michael N. Spilde Stephen Cabaniss Abdul-Mehdi S. Ali Jose M. Cerrato Eliane El Hayek 2018 <p><span>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</span>₃^–<span>&nbsp;solutions at circumneutral pH. The accumulation of U in plants (3.1–21.3 mg kg</span>^–1<span>) from the stream bank of the Rio Paguate, Jackpile Mine, New Mexico served as a motivation for this study.&nbsp;</span><i>Brassica juncea</i><span>was the model plant used for the laboratory experiments conducted over a range of U (30–700 μg L</span>^–1<span>) and Ca (0–240 mg L</span>^–1<span>) concentrations. The initial U uptake followed pseudo-second-order kinetics. The initial U uptake rate (</span><i>V</i>₀<span>) ranged from 4.4 to 62 μg g</span>^–1<span>&nbsp;h</span>^–1<span>&nbsp;in experiments with no added Ca and from 0.73 to 2.07 μg g</span>^–1<span>&nbsp;h</span>^–1<span>&nbsp;in experiments with 12 mg L</span>^–1<span>&nbsp;Ca. No measurable U uptake over time was detected for experiments with 240 mg L</span>^–1<span>&nbsp;Ca. Ternary Ca–U–CO</span>₃<span>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.</span></p> application/pdf 10.1021/acs.est.8b02724 en ACS Effect of calcium on the bioavailability of dissolved uranium(VI) in plant roots under circumneutral pH article