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      https://www.ias.ac.in/article/fulltext/jess/117/06/0935-0943

    • Keywords

       

      Anaerobic oxidation of methane (AOM); sulfate reduction; pore-water; South China Sea.

    • Abstract

       

      The concentrations of CH4, SO$^{2−}_{4}$, 𝛴 CO2 and the carbon isotope compositions of 𝛴 CO2 and CH4 in the pore-water of the GS sedimentary core collected from Guishan Island (Pearl River Estuary), South China Sea,were determined. The methane concentration in the pore-water shows dramatic changes and sulfate concentration gradients are linear at the base of the sulfate reduction zone for the station. The carbon isotope of methane becomes heavier at the sulfate-methane transition (SMT)likely because of the Raleigh distillation effect; 12CH4 was oxidized faster than 13CH4 and this caused the enrichment of residual methane 𝛿13C and 𝛿13C-𝛿 CO2 minimum. The geochemical profiles of the pore-water support the existence of anaerobic oxidation of methane (AOM), which is mainly controlled by the quality and quantity of the sedimentary organic matter. As inferred from the index of 𝛿13C-TOC value and TOC/TN ratio, the organic matter is a mix of mainly refractory terrestrial component plus some labile alga marine-derived in the study area. A large amount of labile organic matter (mainly labile alga marine-derived) is consumed via the process of sedimentary organic matter diagenesis, and this reduces the amount of labile organic matter incorporated into the base of the sulfate reduction zone. Due to the scarcity of labile organic matter, the sulfate will in turn be consumed by its reaction with methane and therefore AOM takes place.Based on a diffussion model, the portion of pore-water sulfate reduction via AOM is 58.6%,and the percentage of 𝛴 CO2 in the pore-water derived from AOM is 41.4%. Thus, AOM plays an important role in the carbon and sulfur cycling in the marine sediments of Pearl River Estuary.

    • Author Affiliations

       

      Zijun Wu1 2 Huaiyang Zhou1 Xiaotong Peng1 Nan Jia2 Yuhong Wang3 Linxi Yuan2

      1. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200 092, China.
      2. Institute of Polar Environment, University of Science and Technology of China, Hefei, Anhui 230 026, China.
      3. National Institute of Health, Bethesda, Maryland 20892, USA.
    • Dates

       
  • Journal of Earth System Science | News

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