Hydrogeochemistry and Water Chemistry
Deducing the Distribution of Terminal Electron-Accepting Processes in Hydrologically Diverse Groundwater Systems
Article first published online: 9 JUL 2010
Copyright 1995 by the American Geophysical Union.
Water Resources Research
Volume 31, Issue 2, pages 359–371, February 1995
How to Cite
1995), Deducing the Distribution of Terminal Electron-Accepting Processes in Hydrologically Diverse Groundwater Systems, Water Resour. Res., 31(2), 359–371, doi:10.1029/94WR02525., , , , , and (
- Issue published online: 9 JUL 2010
- Article first published online: 9 JUL 2010
- Manuscript Accepted: 26 SEP 1994
- Manuscript Received: 19 MAY 1994
The distribution of microbially mediated terminal electron-accepting processes (TEAPs( was investigated in four hydrologically diverse groundwater systems by considering patterns of electron acceptor (nitrate, sulfate) consumption, intermediate product (hydrogen (H2)) concentrations, and final product (ferrous iron, sulfide, and methane) production. In each hydrologic system a determination of predominant TEAPs could be arrived at, but the level of confidence appropriate for each determination differed. In a portion of the lacustrine aquifer of the San Joaquin Valley, for example, all three indicators (sulfate concentrations decreasing, H2 concentrations in the 1–2 nmol range, and sulfide concentrations increasing along flow paths identified sulfate reduction as the predominant TEAP, leading to a high degree of confidence in the determination. In portions of the Floridan aquifer and a petroleum hydrocarbon-contaminated aquifer, sulfate reduction and methanogenesis are indicated by production of sulfide and methane, and hydrogen oncentrations in the 1–4 nmol and 5–14 nmol range, respectively. However, because electron acceptor consumption could not be documented in these systems, less confidence is warranted in the TEAP determination. In the Black Creek aquifer, no pattern of sulfate consumption and sulfide production were observed, but H2 concentrations indicated sulfate reduction as the predominant TEAP. In this case, where just a single line of evidence is available, the least confidence in the TEAP diagnosis is justified. Because this methodology is based on measurable water chemistry parameters and upon the physiology of microbial electron transfer processes, it provides a better description of predominant redox processes in groundwater systems than more traditional Eh-based methods.