Abnormally High CH4 Concentrations in Seawater at Mid-Depths on the Continental Slopes of the Northern South China Sea

Abstract

ABSTRACT1 Institute of Marine Geology and Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC * Corresponding author address: Prof. Chen-Tung Arthur Chen, Institute of Marine Geology and Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC; E-mail: ctchen@mail.nsysu. edu.twFor the first time, CH 4 concentrations in the water column were measured during three cruises in the northern South China Sea. The abnormally high subsurface CH 4 concentrations that were found on the continental slopes may have been released from sediments and/or may have originated in CH 4 gas hydrates.

Methane Venting in Gas Hydrate Potential Area Offshore of SW Taiwan: Evidence of Gas Analysis of Water Column Samples

“…Such shallow methane enrichment may be due to bacteria activity in seawater close to the surface. This result is similar to the recent work of Chen and Tseng (2006) in this area.…”

Extremely High Methane Concentration in Bottom Water and Cored Sediments from Offshore Southwestern Taiwan

“…In order to study the unusual values at one station, dissolved methane concentrations at different depths of the water column (e.g., Chen and Tseng 2006;Yang et al 2006) and methane concentration of pore spaces at different depths of cored samples need to be taken into consideration.…”

Preface to the Special Issue on Gas Hydrate Research around the South China Sea and Taiwan

“…Lin et al (2006) show a very fast sulfate reduction rate in pore waters from cored sediments in the northern part of continental margin of the South China Sea. Very high methane concentrations were also found in both bottom water ) and pore space of cored sediments Oung et al 2006), and also water column samples (Chen and Tseng 2006;, especially in the active margin of the study area. Overall, all the geochemical data, including high methane and dissolved sulfide concentration, high sulfate reduction rate, shallow depth of sulfate-methane-interface, and the carbon isotopic composition of the authigenic carbonates etc., support the conclusion that there is/was a very high methane flux and actively venting in the gas hydrate potential area offshore of SW Taiwan.…”