Spectroscopic evidence of uranium immobilization in acidic wetlands by natural organic matter and plant roots.
Environ Sci Technol
; 49(5): 2823-32, 2015 Mar 03.
Article
em En
| MEDLINE
| ID: mdl-25634067
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 â¼2.88 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.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Urânio
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Raízes de Plantas
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Áreas Alagadas
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Espectroscopia por Absorção de Raios X
Idioma:
En
Ano de publicação:
2015
Tipo de documento:
Article