Biodegradation of Petroleum Hydrocarbons in Fractured, Unsaturated Dolomite at a Field Site |
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| Authors: | Eugene L. McLinn Bernd W. Rehm |
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| Affiliation: | Eugene L. McLinn;earned a B.A. in geology from Macalester College in 1983, and an M.S. in geology from the University of Wisconsin-Milwaukee in 1986. He is currently a senior project hydrogeologist at RMT (RMT Inc., 744 Heartland Trail, Madison, WI 53717). Current work includes the investigation and remediation of contaminated soil and ground water, especially with regard to flow and transport in fractured systems and natural attenuation of contaminants. Bernd W. Rehm;received an M.S. from the University of Waterloo in 1977. He is currently a senior consultant at RMT (RMT Inc., 744 Heartland Trail, Madison WI 53717), and is involved in the characterization, assessment, and remediation of contaminated soils, ground water, and sediments. |
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| Abstract: | Gasoline constituents were detected in unsaturated soil and rock during abandonment of a leaky underground storage tank (UST). The unsaturated sequence beneath the former UST consists of 90 feet of silty till, fractured dolomite, and friable sand-stone. Pore gas probes were installed in each of the unsaturated units, both in the source area and in a background on-site location. Pore gas samples were collected to evaluate the nature, extent, and fate of residual hydrocarbons in the vadose zone. Pore gas from the till and dolomite in the source area was enriched in petroleum hydrocarbons and carbon dioxide, and was depleted in oxygen, relative to pore gas from the background area. During two years of ground water monitoring at the site, methyl tertiary butyl ether was periodically detected in the ground water beneath the source area as pulses of recharge passed through the unsaturated zone, but no other gasoline constituents were detected. Apparently, the most degradable fraction of the gasoline (aromatic hydrocarbons) is being attenuated in the vadose zone before the water table is reached. |
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