Microbial ecology and carbon cycling in Texas aquifers

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5809645

Zhang, Chuanlun; Grossman, E L ^[1]; MacRae, M; Ammerman, J W ^[2]

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1. Texas A and M Univ., College Station, TX (United States). Dept. of Geology
2. Texas A and M Univ., College Station, TX (United States). Dept. of Oceanography

To evaluate the relationship between microbial activity and carbon cycling in the subsurface, the authors performed geochemical and microbiological analyses on ground-waters from 15 wells in three aquifers in Texas--the Edwards (Ed), the Wilcox-Carrizo (WC), and the Sparta-Queen City (SQC). Samples were collected from 128 to 976 m depth. Total bacteria enumerated by direct count methodology range from 1.6 [times] 10[sup 3] to 4.0 [times] 10[sup 4] cells/ml. In both the (SQC) and (WC) aquifers, total bacterial counts decrease with depth. Total counts in (SQC) waters decrease from 6 [times] 10[sup 3] cells/ml at 217 m to 2 [times] 10[sup 3] cells/ml at 616 m; total counts in (WC) waters decrease from 32 [times] 10[sup 3] cells/ml at 369 m to [approximately]5 [times] 10[sup 3] cells/ml at 907 m. Except for two wells, all of the waters contained trace to large amounts of methane. Carbon isotopic analyses of dissolved and head-gas methane range from [minus]80 to [minus]9[per thousand]. Light [delta] C-13 values for methane indicate methane production by bacteria without secondary alteration while heavy [delta] C-13 values for methane strongly suggest methane oxidation, probably by sulfate reduction. delta C-13 values of DIC for high bicarbonate waters indicate a source of CO[sub 2] associated with methanogenesis through fermentation reactions and CO[sub 2] reduction. No correlation is found between the response to the archaebacterial probe and methane content in water, probably due to the limited sensitivity of the archaebacterial probe. However, anaerobic laboratory incubations of water samples in nutrient media showed significant production of methane for all cultured samples except those showing isotopic evidence for methane oxidation. This suggests that methanogens may be present in all waters except those in which methane oxidation has occurred.

• OSTI ID: 5809645
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKANES
AQUIFERS
BACTERIA
BIOASSAY
BIOGEOCHEMISTRY
BIOSYNTHESIS
CARBON 13
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON ISOTOPES
CARBON OXIDES
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
COMPARATIVE EVALUATIONS
DEVELOPED COUNTRIES
EVALUATION
EVEN-ODD NUCLEI
GEOCHEMISTRY
GROUND WATER
HYDROCARBONS
HYDROGEN COMPOUNDS
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
METHANE
METHANOGENIC BACTERIA
MICROORGANISMS
NORTH AMERICA
NUCLEI
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
STABLE ISOTOPES
SULFATE-REDUCING BACTERIA
SYNTHESIS
TEXAS
USA
WATER