Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Evening Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS17] Gas hydrates in environmental-resource sciences

Tue. May 22, 2018 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Hitoshi Tomaru(Department of Earth Sciences, Chiba University), Akihiro Hachikubo(Kitami Institute of Technology), Atsushi Tani(神戸大学 大学院人間発達環境学研究科, 共同), Shusaku Goto(Institute for Geo-Resources and Environment National Institute of Advanced Industrial Science and Technology)

[MIS17-P04] Comparison of methane generation between submarine and sublacustrine environments - the Sea of Okhotsk, Japan Sea, and Lake Baikal -

*Yuki KIkuchi1, Akihiro Hachikubo1, Oleg Khlystov2, Gennadiy Kalmychkov3, Marc De Batist4, Young K. Jin5, Anatoly Obzhirov6, Hirotoshi Sakagami1, Hirotsugu Minami1, Satoshi Yamashita1 (1.Kitami Institute of Technology, 2.Limnological Institute, SB RAS, 3.Vinogradov Institute of Geochemistry, SB RAS, 4.Ghent University, 5.Korea Polar Research Institute, 6.Pacific Oceanological Institute, FEB RAS)

Keywords:gas hydrate, methane, Sea of Okhotsk, Japan Sea, Lake Baikal

In the framework of international collaboration SSGH (Sakhalin Slope Gas Hydrate, 2007-2015) and MHP (Multi-phase Gas Hydrate Project, 2009-2018), Environmental and Energy Resources Research Center, Kitami Institute of Technology has collected many gas samples from submarine and sublacustrine environments where near-surface gas hydrate exists. In this report, we focus on more than 3,000 data of sediment gas using a headspace gas method, and discuss the environments of methane generation under sea and fresh waters.

The sediment gas, mainly dissolved gases in pore water, was obtained by the headspace gas method. 10 mL sediment was sampled from the sediment core by a plastic syringe (volume: 5 mL) and put into a 25 mL vial. 10 mL NaCl aqueous solution (saturated) was introduced into the vial by using a micropipette and sealed employing a butyl rubber septum to make a headspace. To avoid any changes in the headspace, the headspace part was flushed by helium. We measured the molecular and isotopic compositions of headspace gases using gas chromatograph and CF-IRMS in our laboratory.

Methane δ13C in almost all samples are plotted between -100‰ and -40‰ in both submarine and sublacustrine environments. On the other hand, distribution of CO2 δ13C in marine and sublacustrine environments are different with each other: the former between -60‰ and +20‰ and the latter between -20‰ and +30‰. Light CO2 in the sea-bottom sediment are produced by an oxidation of light methane around the SMI depth, so-called a methane recycling process (Borowski et al., 1997).

Our data includes not only the field of microbial methane, but also thermogenic methane in both marine and sublacustrine enviroments. Positive relations of δ13C between methane and CO2 were found in both environments (submarine: Tatar Trough, sublacustrine: Kukuy, PosolBank, and Kedr mud volcanoes). CO2 δ13C with thermogenic methane was larger than that with microbial methane, suggesting the existence of microbial effects even in the thermogenic gas.


Borowski WS, Paull CK, Ussler W III (1997) Carbon cycling within the upper methanogenic zone of continental rise sediments; an example from the methane-rich sediments overlying the Blake Ridge gas hydrate deposits. Mar Chem 57: 299-311