Skip to main content
U.S. flag

An official website of the United States government

Iron reduction in the sediments of a hydrocarbon-contaminated aquifer

January 1, 1999

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 μmol/g) has been reduced by up to 30% from background values (23.8 μmol/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 μmol/g) are as much as 4 times those in the background sediments (4.6 μmol/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.

Citation Information

Publication Year 1999
Title Iron reduction in the sediments of a hydrocarbon-contaminated aquifer
DOI 10.1016/S0883-2927(98)00089-4
Authors M.E. Tuccillo, I.M. Cozzarelli, J.S. Herman
Publication Type Article
Publication Subtype Journal Article
Series Title Applied Geochemistry
Series Number
Index ID 70021520
Record Source USGS Publications Warehouse
USGS Organization Toxic Substances Hydrology Program