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

Eliane El Hayek, Chris Torres, Lucia Rodriguez-Freire, Johanna M. Blake, Cherie L. De Vore, Adrian J. Brearley, Michael N. Spilde, Stephen Cabaniss, Abdul Mehdi S. Ali, José M. Cerrato

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17 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)13089-13098
Number of pages10
JournalEnvironmental Science and Technology
Volume52
Issue number22
DOIs
StatePublished - Nov 20 2018

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

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