Microbial influences on inorganic solute mobilization and transport in an oil contaminated aquifer

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5815079

Bennett, P C; Hiebert, F K ^[1]; Baedecker, M J ^[2]

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1. Univ. of Texas, Austin, TX (United States). Dept. of Geological Sciences
2. Geological Survey, Reston, VA (United States)

Microbial degradation of hydrocarbons in a shallow sand and gravel aquifer contaminated with petroleum results in a distinctive inorganic solute plume that mimics the plume of organic constituents. At the USGS Bemidji, MN research site, microbial control of the geochemical environment beneath a floating pool of oil has resulted in a highly reducing groundwater zone along the major flow path. Within this region, where the fugacity of oxygen is extremely low, microbes utilize naturally occurring iron and manganese minerals as the terminal electron acceptor for the oxidation of hydrocarbons. This results in an increase in ferrous iron concentration from background levels of less than 0.05 mg/l to over 50 mg/l along about 40 meters of the flow path. Dissolved iron concentration remains elevated, and transport of iron occurs, as long as oxygen fugacity remains low. In the reducing zone, petroleum degrading microbes were found to colonize fresh silicate surfaces. Extracellular byproducts of metabolism, such as organic acids, are found in the contaminated groundwater, and these compounds may be present at very high levels near the attached microbial colonies, resulting in a highly reactive micro-environment. Where attached microbial colonies were found, rapid chemical weathering of both quartz and feldspar occurred, producing distinctive and pronounced chemical etching. Dissolved silica is apparently meta-stable in the highly reducing, organic-rich groundwater, and dissolved silica concentration is near equilibrium with amorphous silica gel. Silica is transported along the major flow path until oxygen fugacity increases, and degradation of organic carbon accelerates. Here silica precipitates as silica plastering on silicate minerals. Silica precipitation is coincident with the iron precipitation, and the two processes may be linked, although iron-silicate clays have not been isolated from the site.

• OSTI ID: 5815079
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020900* -- Petroleum-- Environmental Aspects
560300 -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AQUIFERS
BIODEGRADATION
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELEMENTS
ENVIRONMENTAL TRANSPORT
GEOCHEMISTRY
GROUND WATER
HYDROGEN COMPOUNDS
IRON
LAND POLLUTION
MANGANESE
MASS TRANSFER
METALS
MINERALS
MONITORING
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDATION
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PETROLEUM PRODUCTS
PLUMES
POLLUTION
PRECIPITATION
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
TRANSITION ELEMENTS
WATER