A mass balance of C-13 and C-12 in an organic-rich methane-producing marine sediment
A mass balance of C-13 and C-12 in an organic-rich methane-producing marine sediment
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DOI：
10.1016/0016-7037(96)00204-9
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发表时间：
1996-10-01
影响因子：
5
通讯作者：
Martens, CS
中科院分区：
文献类型：
--
作者：
Boehme, SE;Blair, NE;Martens, CS
在美国北卡罗莱纳望台角8号具有良好特征的海岸遗址，确定了C-12和C-13的沉积收支平衡。有机碳的δ (13)C值为-19.2 +/- 0.2‰，通过硫酸盐还原和甲烷生成进行降解。这两种过程都无法检测到最终被掩埋的固相有机组分的C-13/C-12组成。再矿化碳（Sigma CCO2 + CH4）的年平均δ (13)C为-18.7 +/- 2.2‰，这表明固相有机物分解为溶解的中间体对C-13和C-12没有区别。有机质成岩过程中表现的主要碳同位素效应与产甲烷作用有关。该地点产生的甲烷的年平均δ (13)C值为-58.9 +/- 1.4‰。由于(CH4)- c -12的优先合成，Sigma CO2富集C-13 （-11.0 +/- 1.2 ppm）。西格玛CO2和CH4的相对生成速率受可代谢有机碳的沉积通量控制，以及与甲烷生成相关的分馏因子和源碳的同位素组成决定了两种成岩终产物的C-13/C-12含量。
The sedimentary budgets of C-12 and C-13 were determined for the well-characterized coastal site of Cape Lookout Eight, North Carolina, USA. Degradation of organic carbon with a delta(13)C value of -19.2 +/- 0.2 parts per thousand proceeds via sulfate reduction and methanogenesis. Neither process detectably alters the C-13/C-12 composition of the solid phase organic fraction that is ultimately buried. The remineralized carbon (Sigma CCO2 plus CH4) has an annual mean delta(13)C of -18.7 +/- 2.2 parts per thousand, indicating that the breakdown of solid phase organic material to dissolved intermediates does not discriminate between C-13 and C-12.The dominant carbon isotope effect expressed during the diagenesis of the organic matter is associated with methanogenesis. Methane produced at this site has a measured annual mean delta(13)C value of -58.9 +/- 1.4 parts per thousand. The Sigma CO2 is enriched in C-13 (-11.0 +/- 1.2 parts per thousand) because of the preferential synthesis of (CH4)-C-12. The relative rate of production of the Sigma CO2 and CH4, which is controlled by the depositional flux of metabolizable organic carbon, along with the fractionation factor associated with methanogenesis and the isotopic composition of the source carbon, determine the C-13/C-12 content of the two diagenetic endproducts.