Pathways of aqueous Cr(VI) attenuation in a slightly alkaline oxic subsurface.

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Environ. Sci. Technol.

DOI:https://doi.org/10.1021/es802658x· OSTI ID:1008270

Qafoku, N P; Evan Dresel, P; McKinley, J P; Liu, C; Heald, S M; Ainsworth, C C; Phillips, J L; Fruchter, J S ^[1]

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1. X-Ray Science Division

Column experiments combined with geochemical modeling, microscopic inspections, spectroscopic interrogations, and wet chemical extractions were used to study sediment-dependent Cr(VI) desorption, physical location, mineral association, and attenuation mechanism(s) in four freshly or naturally aged contaminated sediments exposed to concentrated Cr(VI) waste fluids. Results showed that majority of Cr(VI) mass was easily removed from the sediments (equilibrium site K{sub d} varied from 0 to 0.33 mL g{sup -1} and equilibrium site fraction was greater than 95%). Long tailings of time-dependent Cr(VI) concentrations above maximum contaminant level of 1.9 {micro}mol L{sup -1} were also observed (kinetically controlled fraction K{sub d} and desorption reaction half-lives varied from 0 to 45 mL g{sup -1}, and from 76.1 to 126 h, respectively). Microscopic and spectroscopic measurements confirmed that Cr was concentrated within fine-grained coatings in small areas mainly rich in phyllosilicates that contained both Cr(III) and Cr(VI). However, Cr(VI) reduction was neither significant nor complete. Under slightly alkaline and oxic conditions, contaminant Cr in the sediments occurred: (i) In the highly mobile pool (over 95% of total Cr); (ii) In the slow and time-dependent releasing pool, which served as long-term source of contamination; (iii) As reduced Cr(III) which most likely formed during Cr(VI) reaction with aqueous, sorbed, or structural Fe(II).

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: EM
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1008270
• Report Number(s): ANL/XSD/JA-63289
• Journal Information: Environ. Sci. Technol., Journal Name: Environ. Sci. Technol. Journal Issue: 4 ; Jan. 2009 Vol. 43; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

54 ENVIRONMENTAL SCIENCES
ATTENUATION
COATINGS
CONTAMINATION
DESORPTION
SEDIMENTS
SIMULATION
TAILINGS
WASTES