日本海東縁MD179コア表層堆積物中の硫黄同位体組成

抄録

Bacterial sulfate reduction affects the sulfur isotopic composition of dissolved (sulfate ion) and solid species (sulfide and elemental sulfur) in the sediment core samples of MD179-3312, eastern margin of Japan Sea. Our dataset includes the sulfate concentration and δ³⁴S of interstitial water, the total sulfur contents and δ³⁴S, and the content of elemental sulfur in the squeezed cake and freeze dry sediment samples.
Sulfur isotopic composition of the freeze-dried samples including pore water is significantly different from the value of the seawater. Total sulfur content of approximately 10 times the amount of sulfate ions contained in seawater have been measured. This composition was formed by sulfate reduction of seawater sulfate ion supplied by in an open system. Sulfur isotopic composition of sediment decrease of up to 139 cm depth from the surface, and then become almost constant.
After an initial fractionation by sulfate reduction, through a repeated cycle of sulfide oxidation to elemental sulfur and subsequent disproportionation, sulfate reducing bacteria can deplete sedimentary sulfides in ³⁴S. The extremely light isotopic composition of sulfur in the sediment indicates an open system bacterial sulfate reduction.
This study is supported by MH21, Research Consortium for Methane Hydrate Resources in Japan.