Quantification of methanogenic pathways using stable carbon isotopic signatures: a review and a proposal
Quantification of methanogenic pathways using stable carbon isotopic signatures: a review and a proposal
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DOI：
10.1016/j.orggeochem.2004.09.006
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发表时间：
2005-01-01
影响因子：
3
通讯作者：
Conrad, R
中科院分区：
文献类型：
--
作者：
Conrad, R
在大多数环境中，CH4是由乙酸酯(即甲基)和氢/二氧化碳作为前体产生的。当测量甲烷产生地点的二氧化碳、甲烷和乙酸甲酯的稳定碳同位素特征，并且已知二氧化碳和乙酸甲酯转化为甲烷的同位素分馏系数时，可以量化这两种产甲烷途径对总甲烷产量的相对贡献。文献综述表明，分馏系数不是常量，而是不同地点和不同条件下的差异，有时是很大的差异。从微生物培养的研究中也可以明显看出巨大的差异。需要更多的数据，特别是明确测定不同条件和环境下的分馏系数。环境条件下分馏系数的实验测定可以通过刺激或抑制实验来完成，这些实验允许在不同的反应中测量稳定的碳分馏。乙酸甲酯周转过程中的同位素分馏是一个特别的挑战，因为乙酸甲酯可能通过几种相互竞争的途径生产和消费。醋酸酯可从有机碳或二氧化碳中生产，并可通过转化为甲烷、二氧化碳或生物质来消费。在生产地点(例如湿地)排放的甲烷中使用同位素特征需要更复杂的模型，因为在所产生的甲烷的运输和氧化过程中还会发生同位素歧视。(C)2004爱思唯尔有限公司。保留所有权利。
In most environments, CH4 is produced from acetate (i.e. the methyl group) and H-2/CO2, as precursors. The relative contribution of these two methanogenic pathways to total CH4 production can be quantified when the stable carbon isotopic signatures Of CO2, CH4 and acetate methyl are measured for the CH4 production site and the isotopic fractionation factors are known for the conversion of CO2 and of acetate methyl to CH4. Literature review shows that the fractionation factors are not constants but differ, sometimes substantially, from site to site and from condition to condition. Large differences are also evident from studies of microbial cultures. More data, in particular explicit determination of fractionation factors under various conditions and environments are required. Experimental determination of fractionation factors under environmental conditions may be done by stimulation or inhibition experiments that allow the measurement of stable carbon fractionation in distinct reactions. Isotopic fractionation during acetate turnover is a particular challenge, since acetate methyl may be produced and consumed by several competing pathways. Acetate may be produced from organic carbon or from CO2 and may be consumed by conversion to CH4, CO2 or biomass. Use of isotopic signatures in CH4 emitted from a production site (e.g. a wetland) requires even more complex models, since isotopic discrimination in addition occurs during transport and oxidation of the CH4 produced. (C) 2004 Elsevier Ltd. All rights reserved.