Anaerobic oxidation of methane: Geochemical evidence from pore-water in coastal sediments of Qi’ao Island (Pearl River Estuary), southern China

查看全文 作　　者：WU [1,2]Zijun;ZHOU [1]Huaiyang;PENG [1]Xiaotong;CHEN [1]Guangqian 机构地区：[1]Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;[2]Graduate School of Chinese Academy of Sciences, Beijing 100039, China 出　　处：《Chinese Science Bulletin》索引2006年第51卷第16期,共10页 摘　　要：The concentrations of CH4 and SO42? in pore-water and the carbon isotope compositions of total dissolved inorganic (ΣCO2) and CH4 were de- termined for three coastal sedimentary cores col- lected from Qi’ao Island (Pearl River Estuary), southern China. Results show that methane concen- tration changes dramatically at the base of the sul- fate-reducing zone and sulfate concentration gradi- ents are linear for all stations. In addition, the carbon isotope of methane becomes heavier at the sul- fate-methane transition (SMT), which causes ΣCO2-δ 13C to become the minimum. The geo- chemical profiles of pore-water render indirect evi- dence for anaerobic oxidation of methane (AOM). Based on numerical modeling of AOM and sul- fate-reducing rates, the portion of total sulfate reduc- tion occurring via AOM is 9.0%, 84% and 45.5%, re- spectively, and the percentage of ΣCO2 added to the pore-water is 4.7%, 72.4% and 29.45% correspond- ingly for three sites. Furthermore, it is found that the methane concentration, methane diffusive flux and the depth of SMT are controlled by the quantity and quality of sedimentary organic matter incorporated into the sediments. The great amount of organic material is favorable for rapid depletion of sulfate via sedimentary organic matter degradation, and on the other hand, causes the increase of the methane flux in the SMT, which results in a portion of sulfate re-duction supported by AOM. Accordingly, the SMT was shifted towards the sediment surface. 关 键 词：缺氧氧化 甲烷 硫酸盐 沉积 珠江河口 地球化学