Flux and source assessment of shallow methane (CH4) gas from sediments in the central Yellow Sea, off the southwest of Korea

Abstract

Methane (CH4) among the gases is the most abundant hydrocarbon in the atmosphere, plays an important role in regulating the Earths radiation balance and atmospheric chemistry in the troposphere. CH4 in the headspace gas were determined in surface and core sediments in order to understand the carbon and hydrogen isotopes signatures collected in the Gunsan Basin of the central Yellow Sea from 2013 to 2015. The surface sediments contain 0.2 to 16.9 (&micro M) CH4 that are mostly produced, as indicated by the light values of δ13CCH4 range in &#8211 70.2~-50.7 (‰) VPDB (Vienna Pee Dee Belemnite). The geochemical characteristics values of δ13CCH4 range in &#8211 62.0~-18.0 (‰) VPDB (δ2DCH4 range in &#8211 296.0~-144.0 (‰) VSMOW (Vienna Standard Mean Ocean Water)), that is, strongly mixed CH4 of thermogenic and biogenic origins through the core sediments. The CH4 flux at the SWI (Sediment-Water Interface) using Fick’s first law of diffusion was calculated 2~29 (&micro M·m-2·day-1) within the uppermost 10 cm sediment layer of box corer in 2015. However, more detailed study is needed to reveal clearly the migration pathways and more measurements on the methane emission rates during different seasons in this area required assessment the annual CH4 distribution and flux in detail. surface and core sediments in order to understand the carbon and hydrogen isotopes signatures collected in the Gunsan Basin of the central Yellow Sea from 2013 to 2015. The surface sediments contain 0.2 to 16.9 (&micro M) CH4 that are mostly produced, as indicated by the light values of δ13CCH4 range in &#8211 70.2~-50.7 (‰) VPDB (Vienna Pee Dee Belemnite). The geochemical characteristics values of δ13CCH4 range in &#8211 62.0~-18.0 (‰) VPDB (δ2DCH4 range in &#8211 296.0~-144.0 (‰) VSMOW (Vienna Standard Mean Ocean Water)), that is, strongly mixed CH4 of thermogenic and biogenic origins through the core sediments. The CH4 flux at the SWI (Sediment-Water Interface) using Fick’s first law of diffusion was calculated 2~29 (&micro M·m-2·day-1) within the uppermost 10 cm sediment layer of box corer in 2015. However, more detailed study is needed to reveal clearly the migration pathways and more measurements on the methane emission rates during different seasons in this area required assessment the annual CH4 distribution and flux in detail.