The goal of this interdisciplinary study is to better understand how spatial and temporal variation in aqueous geochemistry and microbial community structure affects the intrinsic bioremediation of fuel and chlorinated solvents. Our sampling program is designed to : (1) determine the dominant terminal electron accepting process (TEAP) by measuring the H2 gas concentration of ground water; (2) determine patterns of microbial community DNA composition in sediments taken from each TEAP zone, by using amplified ribosomal DNA restriction analysis (ARDRA) and denaturing gradient gel electrophoresis (DGGE); and (3) determine patterns in the distribution and abundance of TEAP-specific microbial populations (e.g., methanogens, sulfate-reducers) by using hybridization to 16S rRNA extracted from aquifer sediments.
On three dates, we sampled ground water in a shallow, sandy aquifer contaminated with jet fuel and chlorinated solvents. Samples taken from five multi-level wells and 2 single-depth wells were analyzed for redox chemistry (NO3, NH4, Fe(II), SO4, and CH4), and nucleic acids were extracted from aquifer sediments taken from each TEAP zone. For the last two sample sets, we also determined major ions and contaminant chemistry. Preliminary results suggest that there are dramatic (but logical and predictable) spatial and temporal changes in TEAPs at this site, and that microbial community DNA composition (ARDRA and DGGE patterns) for a given location in the aquifer changes with the TEAP. Preliminary 16S rRNA hybridization data suggest that methanogens (or other Archaea) are most abundant in sediments where the TEAP indicates methanogenesis during some part of the year. Once determined and accounted for, knowledge of site geochemical and microbiological heterogeneity can be used to refine sampling strategies and monitoring programs, improve the reproducibility of field and laboratory tests for biodegradation, and develop more accurate models.
Haack, S.K., Forney, L.J., Adriaens, Peter, and Chapelle, F.H., 1997, Temporal Heterogeneity in Aqueous Geochemistry and Microbiology of a Contaminated Aquifer: Eos, Transactious, American Geophysical Union, 1997 Spring Meeting, v. 78, no. 17.
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