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Iron reduction in the sediments of a hydrocarbon-contaminated aquifer

Applied Geochemistry

By:
, ,
DOI: 10.1016/S0883-2927(98)00089-4

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Abstract

Sediments sampled at a hydrocarbon-contaminated, glacial-outwash, sandy aquifer near Bemidji, Minnesota, were analyzed for sediment-associated Fe with several techniques. Extraction with 0.5 M HCl dissolved poorly crystalline Fe oxides and small amounts of Fe in crystalline Fe oxides, and extracted Fe from phyllosilicates. Use of Ti-citrate-EDTA-bicarbonate results in more complete removal of crystalline Fe oxides. The average HCl-extractable Fe(III) concentration in the sediments closest to the crude-oil contamination (16.2 ??mol/g) has been reduced by up to 30% from background values (23.8 ??mol/g) as a result of Fe(III) reduction in contaminated anoxic groundwater. Iron(II) concentrations are elevated in sediments within an anoxic plume in the aquifer. Iron(II) values under the oil body (19.2 ??mol/g) are as much as 4 times those in the background sediments (4.6 ??mol/g), indicating incorporation of reduced Fe in the contaminated sediments. A 70% increase in total extractable Fe at the anoxic/oxic transition zone indicates reoxidation and precipitation of Fe mobilized from sediment in the anoxic plume. Scanning electron microscopy detected authigenic ferroan calcite in the anoxic sediments and confirmed abundant Fe(III) oxyhydroxides at the anoxic/oxic boundary. The redox biogeochemistry of Fe in this system is coupled to contaminant degradation and is important in predicting processes of hydrocarbon degradation.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Iron reduction in the sediments of a hydrocarbon-contaminated aquifer
Series title:
Applied Geochemistry
DOI:
10.1016/S0883-2927(98)00089-4
Volume
14
Issue:
5
Year Published:
1999
Language:
English
Publisher:
Elsevier Science Ltd
Publisher location:
Exeter, United Kingdom
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Applied Geochemistry
First page:
655
Last page:
667
Number of Pages:
13