Talk Abstract

The acid volatile sulfide (AVS) content in the sediments of the Yellow Sea and the South China Sea was determined. We found that the AVS content decreased in the following order: Licun estuary in the Jiaozhou Bay > Jiaozhou Bay > the East China Sea continental slope > the Yellow Sea continental shelf > the East China Sea continental shelf > the South China Sea slope. Based upon our results of sulfide, reactive metals, and pyritization of sediment cores collected from the Yellow Sea and South China Sea, and published results of sediments from the East China Sea, we concluded that sediment organic carbon content was the major factor that controlled the formation of sulfide in sediments of the Chinese Marginal Seas. Reactive iron would become the controlling factor only in environments with very high organic carbon supply, such as the Licun estuary. The quantity and quality of organic matter, sedimentation rate, redox condition, bottom water temperature, and burial time all could influence the formation, quantity and transform of sulfides in the sediments. 

In sediment core NH-1, retrieved from the South China Sea, a pyrite content maximum was found at the depth of 141.5cm. Extensive sulfate reduction took place at depths between 120-141.5cm. Combining previous results obtained from cores collected to the west of our core, we thought that the depth of 141.5cm might represent the boundary of Late Pleistocene glacial and Holocene post-glacial period. The high AVS contents appeared near the bottom of the sediment core, which was abnormal as AVS in most marine sediments had mid-depth maximum. Both δ³⁴S of pyrite and AVS content showed abnormal value at the 247.5～380.5cm interval of the sediment core NH-1, suggesting intensive methane upward flux and possibly the formation of gas-hydrate at greater depth at this location.