Effect of calcium on the bioavailability of dissolved uranium(VI) in plant roots under circumneutral pH

Environmental Science & Technology
By: , and 

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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 junceawas 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–CO3complexes 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.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Effect of calcium on the bioavailability of dissolved uranium(VI) in plant roots under circumneutral pH
Series title Environmental Science & Technology
DOI 10.1021/acs.est.8b02724
Volume 52
Issue 22
Year Published 2018
Language English
Publisher ACS
Contributing office(s) New Mexico Water Science Center
Description 10 p.
First page 13089
Last page 13098