The influence of microbial activity and sedimentary organic carbon on the isotope geochemistry of the Middendorf aquifer

Journal Article · Sun Mar 01 04:00:00 EST 1992 · Water Resources Research; (United States)

DOI:https://doi.org/10.1029/91WR02678· OSTI ID:5149710

Murphy, E M; Schramke, J A; Fredrickson, J K; Sklarew, D S; Linehan, J C ^[1]; Bledsoe, H W ^[2]; Francis, A J ^[3]

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1. Pacific Northwest Lab., Richland, WA (United States)
2. Westinghouse Savannah River Co., Aiken, SC (United States)
3. Brookhaven National Lab., Upton, NY (United States)

In this study, tritium, {sup 14}C, and groundwater chemistry along three flow paths of the Middendorf aquifer in South Carolina were analyzed. The {sup 14}C ranged from 89% modern carbon (pmC) in the recharge zone to 9.9 pmC in the distal borehole. Carbon isotope analyses of particulate organic carbon from core sediments and groundwater chemistry were used to model the carbon chemistry; the groundwater ages obtained from {sup 14}C ranged from modern to 11,500 years B.P. The highest frequencies of occurrence, numbers, and diversity of aerobic and anaerobic bacteria were found in boreholes near the recharge zone where the calculated ages were < 1,000 years B.P. The transport of microorganisms from the recharge zone may be responsible for this distribution as well as the electron acceptors necessary to support this diverse community of bacteria. The presence of both aerobic heterotrophs and anaerobic sulfate- and iron-reducing bacteria in the core sediments suggested the occurrence of anaerobic microsites throughout this otherwise aerobic aquifer. The highest in situ microbial respiration rate, as determines by modeling, was found along a flow path near the recharge area. It is likely that the electron acceptors necessary for supporting a diverse microbial community are depleted by the time the groundwater residence time in the Middendorf aquifer exceeds several hundred years.

• DOE Contract Number: AC06-76RL01830
• OSTI ID: 5149710
• Journal Information: Water Resources Research; (United States), Journal Name: Water Resources Research; (United States) Vol. 28:3; ISSN 0043-1397; ISSN WRERA
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540220* -- Environment
Terrestrial-- Chemicals Monitoring &amp; Transport-- (1990-)
560300 -- Chemicals Metabolism &amp; Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AQUIFERS
BACTERIA
BIODEGRADATION
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CHEMICAL REACTIONS
CHEMISTRY
CONTAMINATION
DECOMPOSITION
DEVELOPED COUNTRIES
GEOCHEMISTRY
GROUND WATER
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MATHEMATICAL MODELS
MICROORGANISMS
NORTH AMERICA
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
POLLUTION
SOUTH CAROLINA
TRACER TECHNIQUES
TRITIUM COMPOUNDS
USA
WATER
WATER CHEMISTRY
WATER POLLUTION