유기화합물 적출에 근거한 메탄 방출: 메카니즘 및 관련된 해양환경

Abstract

More than 70 samples of two piston cores (06GHSA P1 and 06GHSA P6) from the Ulleung Basin of the East Sea were examined for the presence of organic compounds (diploptene), and their carbon isotopic variations were also analyzed to determine their origins. 23 of 70 samples were selected for carbon isotope analysis based on isotope ratio mass spectrometry.Data from the core records showed that organic compounds occurred in the two cores, showing high vertical fluctuation in the 06GHSA P6 core during the Last Glacial Maximum (LGM). The diploptene concentration ranged from 1.7 to 632.1 ng/g (average 87 ng/g) in core 06GHSA P6 and from 1.4 to 42.2 ng/g in core 06GHSA P1 (average 20.1 ng/g). An especially elevated concentration of diploptene was observed in core 06GHSA P6 during glacial periods. Carbon isotope values in the diploptene ranged from –56.33 to –60.23 per mil, suggesting that this diploptene was in part derived from methanotrophic bacteria, which decomposed methane in the water column and sediment. Thus, the occurrence of diploptene derived from bacterial activity and the carbon isotopic values of diploptene may indicate potential methane seepage in core 06GHSA P6. This implies potential dissociation of gas hydrate during glacial periods.Reasons for the release of methane may include paleoceanographic environmental changes such as in sea level. Unlike the Santa Barbara basin1 in which the episodic light carbon isotopic signals were interpreted as the reason for the warm intermediate water inflow, in the East Sea, the lowered sea level and climatic changes during glacial period may have reduced the stability of the methane hydrate. Schematic model for the methane seepage is suggested in this study.