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Complex hydrogeologic conditions coupled with poorly understood biodegradation processes in karst aquifers have led many to believe that the potential for natural attenuation of petroleum fuel hydrocarbons in karst is limited.1 Ground-water samples were collected for bacteria and geochemical analysis from two monitoring wells (MCI-1 and MCI-4) in a karst bedrock aquifer. Water from the MCI-1 well has consistently tested positive for fuel contamination during the past 3 years of semi-annual monitoring. Water from MCI-4 has been relatively uncontaminated during the same time period. Bacteria concentrations were 50% greater in ground-water samples from the fuel-contaminated well. Additionally, bacteria isolated from fuel-contaminated ground-water samples readily grew in Petri dishes with dissolved toluene and benzene as the only source of food. Water from the less contaminated MCI-4 well had a greater dissolved oxygen concentration (6.4 milligrams per liter) than the fuel-contaminated water (dissolved oxygen less than 0.1 milligrams per liter). Also, where the oxygen concentrations were diminished, geochemical evidence indicated that anaerobic processes were active. This evidence includes elevated levels of ammonia, sulfide, and ferrous iron in the fuel-contaminated ground-water samples. Based on these results, biodegradation of fuel constituents in the karst aquifer is indicated, and therefore, natural attenuation should not be disregarded because of preconceptions about low microbial activity in karst aquifers.
1.This research addressed the capacity for biodegration processes in Karst.
This abstract can be cited as follows:
Minor, Kamalah, Muhammad, Raushanah, Wade, Tavy, Allison, Allyn, and Byl, T.D., 2001, Biodegradation of fuel in a karst aquifer [abs.], in Tennessee Water Resources Symposium, 11th, Burns, Tenn., 2001, Proceedings: Tennessee Section of the American Water Resources Association, p. P-6.
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