HR: 1340h
AN: H13G-1675    [Abstracts]
TI: Microbially Induced Temperature Changes in a Petroleum Hydrocarbon Plume
AU: * Warren, E
EM: ewarren@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, MS 472, Menlo Park, CA 94025, United States
AU: Bekins, B
EM: babekins@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, MS 472, Menlo Park, CA 94025, United States
AB: The degradation reactions of organic contaminants are often exothermic. Given this, the degradation of organic contaminants in an aquifer should produce measurable temperature increases if the heat is generated faster than it is dissipated. The groundwater contaminant plume at a crude oil spill site near Bemidji, Minnesota, USA, has been undergoing aerobic and anaerobic biodegradation for 28 years. At this site, the theoretical degradation of 100 mg/L phenol, a representative compound, under aerobic conditions could generate a 2°C increase in groundwater temperature with no heat loss and an aquifer heat capacity of 2,494 J/L-°C. The temperature in the aquifer was measured with an accurate thermistor (<e;±0.01°C) that was lowered to multiple depths in 13 monitoring wells along a groundwater flowpath. The measurements were taken from 0.15 to 12.62 m below the water table. Temperatures ranged from 6.35°C in the background aquifer to 9.19°C just under the crude oil source. These data revealed a thermal plume co-located with a previously observed area of BTEX biodegradation under iron-reducing and methanogenic conditions. The results indicate that evidence of exothermal microbial reactions within contaminant plumes can be detected using sensitive and detailed temperature measurements in wells.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0432 Contaminant and organic biogeochemistry (0792)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting