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首页> 外文期刊>Geochemistry, geophysics, geosystems >Sources and turnover of organic carbon and methane in fjord and shelf sediments off northern Norway
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Sources and turnover of organic carbon and methane in fjord and shelf sediments off northern Norway

机译：挪威北部海域峡湾和陆架沉积物中有机碳和甲烷的来源和周转

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摘要

To better understand the present and past carbon cycling and transformation processes in methane-influenced fjord and shelf areas of northern Norway, we compared two sediment cores from the Hola trough and from Ullsfjorden. We investigated (1) the organic matter composition and sedimentological characteristics to study the sources of organic carbon (C-org) and the factors influencing C-org burial, (2) pore water geochemistry to determine the contribution of organoclastic sulfate reduction and methanogenesis to total organic carbon turnover, and (3) the carbon isotopic signature of hydrocarbons to identify the carbon transformation processes and gas sources. High sedimentation and C-org accumulation rates in Ullsfjorden support the notion that fjords are important C-org sinks. The depth of the sulfate-methane-transition (SMT) in the fjord is controlled by the supply of predominantly marine organic matter to the sediment. Organoclastic sulfate reduction accounts for 60% of the total depth-integrated sulfate reduction in the fjord. In spite of the presence of ethane, propane, and butane, we suggest a purely microbial origin of light hydrocarbons in the sediments based on their low delta C-13 values. In the Hola trough, sedimentation and C-org accumulation rates changed during the deglacial-to-post-glacial transition from approximately 80 cm ka(-1) to erosion at present. Thus, C-org burial in this part of the shelf is presently absent. Low organic matter content in the sediment and low rates of organoclastic sulfate reduction (only 3% of total depth-integrated sulfate reduction) entail that the shallow depth of the SMT is controlled mostly by ascending thermogenic methane from deeper sources.
机译：为了更好地了解挪威北部受到甲烷影响的峡湾和陆架地区的当前和过去的碳循环和转化过程，我们比较了Hola槽和Ullsfjorden的两个沉积岩心。我们调查了（1）有机物的组成和沉积特征，以研究有机碳的来源和影响C-org埋藏的因素，（2）孔隙水地球化学以确定有机碎屑硫酸盐的还原和甲烷化作用对总有机碳营业额，以及（3）碳氢化合物的碳同位素特征，以识别碳转化过程和气源。阿尔斯峡湾的高沉积和C-org积累速率支持了以下观点：峡湾是重要的C-org汇。峡湾中硫酸盐-甲烷过渡（SMT）的深度由沉积物中主要海洋有机物的供应控制。器官破壁硫酸盐减少占峡湾总深度综合硫酸盐减少的60％。尽管存在乙烷，丙烷和丁烷，但由于其低C-13值，我们建议在沉积物中形成轻烃的纯微生物来源。目前，在Hola槽中，从冰期到冰期后过渡期从大约80 cm ka（-1）到侵蚀，沉积和C-org积累速率发生了变化。因此，目前在架子的该部分中没有C-org埋葬。沉积物中有机物含量低和有机碎屑硫酸盐还原率低（仅占深度综合硫酸盐还原总量的3％），这意味着SMT的浅层深度主要是由来自较深来源的产甲烷甲烷的上升控制的。

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