Carbon Geochemistry of Gas Hydrate-associated Sediments in the Southwestern Taiwan Basin
Carbon Geochemistry of Gas Hydrate-associated Sediments in the Southwestern Taiwan Basin
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台湾盆地西南地区天然气水合物相关沉积物的碳地球化学
DOI：
10.1111/1755-6724.13508
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Shi Chunxiao
中科院分区：
文献类型：
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作者：
Lei Huaiyan;Yang Yufeng;K;asamy Selvaraj;Shi Chunxiao
海洋天然气水合物是地球上最大的甲烷储集层之一，对深海沉积环境和地球化学具有重要影响，但目前对含天然气水合物沉积物中的碳地球化学研究还很薄弱。在这项研究中，我们调查了南海台湾盆地西南部973 - 3沉积物柱样中的碳变量，以了解环境因素和古菌群落对碳地球化学的影响。碳剖面表明，甲烷生成过程中溶解无机碳（DIC）和总有机碳（TOC）含量（平均值为0.46%）的增加主要来自陆源有机质（δ 13 TOC平均值为−23.6±），其驱动力为丰富的产甲烷菌“甲烷菌群和甲烷微生物”。430-840 cm处甲烷厌氧氧化的特征是DIC和无机碳（IC）增加，δ 13 CIC亏损，TOC增加，δ 13 CTOC值下降，这是甲烷营养菌“Methanocinales/ANME”作用的结果。由于甲烷的产生和氧化，973 - 3岩芯中的环境因素和古菌群落与碳变量显著相关。结果表明，碳地球化学特征对天然气水合物的形成和分解有明显的响应。此外，pH值、Eh值、粒度和甲烷含量对水合物沉积物中碳的地球化学特征也有很大影响.
Marine gas hydrates, one of the largest methane reservoirs on Earth, may greatly affect the deep sea sedimentary environment and biogeochemistry; however, the carbon geochemistry in gas hydrate‐bearing sediments is poorly understood. In this study, we investigated the carbon variables in sediment core 973‐3 from the southwestern Taiwan Basin in the South China Sea to understand the effect of environmental factors and archaeal communities on carbon geochemistry. The carbon profiles suggest the methanogenesis with the incerase of dissolved inorganic carbon (DIC) and high total organic carbon (TOC) (mean = 0.46%) originated from terrigenous organic matter (meanδ13CTOCvalue of −23.6±) driven by the abundant methanogen ‘MethanosaetaandMethanomicrobiales'. The active anaerobic oxidation of methane is characterized by the increase of DIC and inorganic carbon (IC), and the depleted δ13CIC, coupled with the increase of TOC and the decrease ofδ13CTOCvalues owing to the methanotroph ‘Methanosarcinales/ANME’ in 430–840 cm. Environmental factors and archaeal communities in core 973‐3 are significantly correlated to carbon variables owing to methane production and oxidation. Our results indicate that the carbon geochemical characteristics are obviously responding to the formation and decomposition of gas hydrates. Furthermore, pH, Eh and grain size, andMethanosaetagreatly affect the carbon geochemistry in gas hydrate‐associated sediments.