Redox Buffer Capacity in Water-Rock-Microbe Interaction Systems in Subsurface Environments

Abstract

An incubation experiment was conducted to estimate redox buffer capacity of “water-rock-microbe” interaction systems in sedimentary rocks. The water chemistry, microbial growth and community structure were analyzed during the incubations. The dissolved oxygen (DO) concentrations and oxidation-reduction potential (ORP) values decreased notably in the presence of active microorganisms, whereas abiotic reactions did not lead to reducing conditions during incubation. The change in microbial community structure suggests that nitrate-reducing and sulfate-reducing bacteria played an important role in reduction of water by using lignite-derived organic matter. These results show that the microbial role is extremely important for the redox buffering capacity in sedimentary rock environments.

Keywords:

• redox buffering capacity
• deep geological disposal of high-level radioactive waste
• water-rock-microbe interaction systems
• lignite
• microbial degradation of high molecular weight organic matter

Acknowledgments

We thank Prof. Takeshi Naganuma and Prof. Hidekazu Yoshida for valuable comments during the course of this study, and Mr. Glen McCrank, Dr. Russel W. Alexander, and Dr. Kazuhiro Aoki for giving comments in preparation for the manuscript. We thank Ms. Akiko Nakanoya for drawing figures for the manuscript. We also express our sincere thanks to the anonymous reviewers who gave invaluable comments.