Spectroscopic evidence of uranium immobilization in acidic wetlands by natural organic matter and plant roots

Dien Li, Daniel I. Kaplan, Hyun Shik Chang, John C. Seaman, Peter R. Jaffe, Paul Koster Van Groos, Kirk G. Scheckel, Carlo U. Segre, Ning Chen, De Tong Jiang, Matthew Newville, Antonio Lanzirotti

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

Biogeochemistry of uranium in wetlands plays important roles in U immobilization in storage ponds of U mining and processing facilities but has not been well understood. The objective of this work was to study molecular mechanisms responsible for high U retention by Savannah River Site (SRS) wetland sediments under varying redox and acidic (pH = 2.6-5.8) conditions using U L3-edge X-ray absorption spectroscopy. Uranium in the SRS wetland sediments existed primarily as U(VI) bonded as a bidentate to carboxylic sites (U-C bond distance at ∼2.88 Å), rather than phenolic or other sites of natural organic matter (NOM). In microcosms simulating the SRS wetland processes, U immobilization on roots was 2 orders of magnitude higher than on the adjacent brown or more distant white sands in which U was U(VI). Uranium on the roots were both U(IV) and U(VI), which were bonded as a bidentate to carbon, but the U(VI) may also form a U phosphate mineral. After 140 days of air exposure, all U(IV) was reoxidized to U(VI) but remained as a bidentate bonding to carbon. This study demonstrated NOM and plant roots can highly immobilize U(VI) in the SRS acidic sediments, which has significant implication for the long-term stewardship of U-contaminated wetlands.

Original languageEnglish (US)
Pages (from-to)2823-2832
Number of pages10
JournalEnvironmental Science and Technology
Volume49
Issue number5
DOIs
StatePublished - Mar 3 2015

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

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    Li, D., Kaplan, D. I., Chang, H. S., Seaman, J. C., Jaffe, P. R., Koster Van Groos, P., Scheckel, K. G., Segre, C. U., Chen, N., Jiang, D. T., Newville, M., & Lanzirotti, A. (2015). Spectroscopic evidence of uranium immobilization in acidic wetlands by natural organic matter and plant roots. Environmental Science and Technology, 49(5), 2823-2832. https://doi.org/10.1021/es505369g