U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings
of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993,
Water-Resources Investigations Report 94-4015
  
Effects of Pb and Terminal-Electron-Accepting Processes on Organic
Acid Concentrations in Contaminated Aquifer Sediments
by
Paul M. Bradley (U.S. Geological Survey, Columbia, South Carolina),
Francis H. Chapelle (U.S. Geological Survey, Columbia, South Carolina),
and Don A. Vroblesky (U.S. Geological Survey, Columbia, South Carolina)
Abstract
The effects of terminal-electron-accepting processes (TEAPs)
and dissolved Pb concentrations on carbon mineralization and
organic acid accumulation in petroleum-contaminated sediments
were examined under aerobic, nitrate reducing, sulfate reducing,
and methanogenic conditions. Pb concentrations in the 14
to 60 µg/L range observed in the field significantly inhibited
CO2 production for all TEAPs as well as CH4 production
under methanogenic conditions. However, accumulation of organic
acids was more closely related to the dominant TEAP. Acetic,
propionic, i-butyric, and n-butyric acids accumulated in
methanogenic treatments, whereas only acetic acid was detected
in sulfate reducing treatments. As expected, no organic
acids were detected under nitrate reducing or aerobic conditions.
This pattern parallels field observations in which high
concentrations of organic acids (acetic, propionic, i-butyric,
and n-butyric acids) were detected in methanogenic zones,
but only low concentrations of acetic acid were detected
in sulfate reducing zones.
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