Proc. IODP, 337, Data report: water activity of the deep coal-bearing basin off Shimokita from IODP Expedition 337

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Chapter contents Abstract Introduction Methods and materials A_w measurements Dependence of A_w on salinity and water content Computation of A_w values from pore water chemistry Porosity measurements Results Depth profile of physical properties Effect of physical and chemical properties on A_w Predicted A_w from water chemistry Acknowledgments References Figures F1. Location, lithology, and biostratigraphy. F2. WP4-T and LabTouch-AW A_w. F3. A_w and porosity. F4. A_w and NaCl, water saturation, and porosity. F5. Measured and predicted A_w. Tables T1. A_w data. T2. Lithologic variation in A_w and physical properties. T3. Physical properties of samples. T4. A_w and pore fluid NaCl. T5. A_w and degree of water saturation. PDF file			Previous \| Next doi:10.2204/iodp.proc.337.204.2018 Data report: water activity of the deep coal-bearing basin off Shimokita from IODP Expedition 337¹ Wataru Tanikawa,^2,³ Yoko Ohtomo,⁴ Glen Snyder,⁵ Yuki Morono,^2,³ Yu’suke Kubo,⁶ Yoshihiro Iijima,⁷ Takuroh Noguchi,⁸ Kai-Uwe Hinrichs,⁹ and Fumio Inagaki^2,^3,¹⁰ Abstract Water activity (A_w) is one of the physicochemical properties that may influence microbial activity in deep subseafloor environments; however, A_w for subseafloor sediments has never been examined, even at shallow depths. This study investigated A_w data obtained from core samples collected during Integrated Ocean Drilling Program Expedition 337 in the deep-water coal-bearing basin off Shimokita, Japan. A_w did not show any depth dependence and was relatively low in coal-bearing layers. A_w at depths of 0–2466 meters below seafloor ranged from 0.95 to 0.98, which is quite high and well suited to sustaining microorganisms. A_w for sedimentary rocks was less affected by lithology and porosity than it was by the NaCl concentration and degree of fluid saturation. In addition, the A_w measurements performed in this study yielded results that corresponded closely with values estimated using Raoult’s law and interstitial water chemistry. It therefore appears that A_w for deep-marine sediments is strongly affected by pore water chemistry. The low A_w anomaly in the coalbed unit is considered to be due to contamination by drilling mud and fluid into core samples. ¹ Tanikawa, W., Ohtomo, Y., Snyder, G., Morono, Y., Kubo, Y., Iijima, Y., Noguchi, T., Hinrichs, K.-U., and Inagaki, F., 2018. Data report: water activity of the deep coal-bearing basin off Shimokita from IODP Expedition 337. In Inagaki, F., Hinrichs, K.-U., Kubo, Y., and the Expedition 337 Scientists, Proceedings of the Integrated Ocean Drilling Program, 337: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.337.204.2018 ² Kochi Institute for Core Sample Research, JAMSTEC, Japan. Correspondence author: tanikawa@jamstec.go.jp ³ Research and Development Center for Submarine Resources, JAMSTEC, Japan. ⁴ Faculty of Engineering, Hokkaido University, Japan. ⁵ Gas Hydrate Research Laboratory, Meiji University, Japan. ⁶ Center for Deep Earth Exploration, JAMSTEC, Japan. ⁷ Graduate School of Bioresources, Mie University, Japan. ⁸ Interdisciplinary Science Unit, Research and Education Faculty, Kochi University, Japan. ⁹ Center for Marine Environmental Sciences, University of Bremen, Germany. ¹⁰ Research and Development Center for Ocean Drilling Science, JAMSTEC, Japan. Initial receipt: 11 April 2017 Acceptance: 13 November 2017 Publication: 22 March 2018 MS 337-204 Top of page \| Previous \| Next