Measuring rates of biodegradation in a contaminated aquifer using field and laboratory methods
- Geological Survey, Columbia, SC (United States)
- Univ. of Massachusetts, Amherst, MA (United States). Dept. of Microbiology
Rates of biodegradation were measured in a petroleum hydrocarbon-contaminated aquifer using a combination of field and laboratory methods. These methods are based on tracking concentration changes of substrates (both electron donors and acceptors) or final products of microbial metabolism over time. Ground water at the study site (Hanahan, South Carolina) is anoxic, and sulfate reduction is the predominant terminal electron accepting process. Laboratory studies conducted with sediment cored from the site showed that {sup 14}C-toluene was mineralized to {sup 14}CO{sub 2} with a first-order degradation rate constant (K{sub tol}) of {minus}0.01 d{sup {minus}1} under sulfate-reducing conditions. Under nitrate-amended, Fe(III)-amended, or nonamended (methanogenic) conditions, toluene was not significantly mineralized. {sup 14}C-Benzene was degraded at low but measurable rates (k{sub ben} = {minus}0.003 d{sup {minus}1}) under sulfate-reducing conditions whereas degradation under methanogenic conditions was negligible. These results illustrate the extreme sensitivity of laboratory-measured biodegradation rates to terminal electron-accepting conditions, and show the necessity of carefully matching experimental conditions to in situ conditions. Concentration decreases of toluene along aquifer flowpaths, when the uncertainty of ground-water flow velocities was considered, indicated k{sub tol} values ranging from {minus}0.0075 to {minus}0.03 d{sup {minus}1}. Concentration decreases of sulfate and concentration increases of dissolved inorganic carbon (DIC), when normalized for assumed stoichiometric oxidation of toluene coupled to sulfate reduction, yielded a k{sub SO{sub 4}} range of {minus}0.005 to {minus}0.02 d{sup {minus}1}, and a k{sub DIC} value range of +0.00075 to +0.003 d{sup {minus}1}. A combination of both laboratory and field methods is the most appropriate procedure for evaluating biodegradation rate constants in contaminated ground-water systems.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 260484
- Journal Information:
- Ground Water, Journal Name: Ground Water Journal Issue: 4 Vol. 34; ISSN GRWAAP; ISSN 0017-467X
- Country of Publication:
- United States
- Language:
- English
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