Characterization of stable isotope fractionation during methane production in the sediment of a eutrophic lake, Lake Dagow, Germany
Characterization of stable isotope fractionation during methane production in the sediment of a eutrophic lake, Lake Dagow, Germany
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DOI：
10.4319/lo.2009.54.2.0457
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发表时间：
2009-03-01
影响因子：
4.5
通讯作者：
Casper, Peter
中科院分区：
文献类型：
--
作者：
Conrad, Ralf;Claus, Peter;Casper, Peter
通过培养实验，测定了富营养化达戈湖深水沉积物中CO2、CH 4和乙酸甲酯的δ C-13，研究了甲烷抑制剂氯仿、溴乙烷磺酸盐（BES）和甲基氟对沉积物中CO2、CH 4和乙酸甲酯δ C-13的影响。甲基氟主要抑制乙酸裂解型甲烷生成，对氢营养型甲烷生成的影响相对较小。甲基氟浓度的优化导致完全抑制乙酸裂解产甲烷。甲烷，然后专门产生的氢营养产甲烷，从而允许确定特定的这种产甲烷途径的分馏因素。然后不再消耗的乙酸盐积累并允许确定发酵产生的乙酸盐的同位素特征。BES和氯仿也抑制CH 4的产生，导致乙酸的积累。氢营养型产甲烷的分馏因子表现出变异性，e。例如，在一个实施例中，随沉积深度的变化而变化。积累的乙酸盐的甲基的δ C-13与沉积有机碳的δ C-13相似，而羧基的δ C-13高出约12 ppm。然而，Δ C-13的乙酸盐是由约千分之五的样品与抑制acetoclastic甲烷生成相比，未受抑制的低，这表明不寻常的同位素分馏。同位素数据用于计算氢营养与乙酸裂解产甲烷对总CH 4产量的相对贡献。随着沉积物深度的增加，氢营养甲烷的贡献从35%增加到60%，这表明有机质在更深的沉积层中仅被部分氧化。
We measured delta C-13 of CO2, CH4, and acetate-methyl in profundal sediment of eutrophic Lake Dagow by incubation experiments in the presence and absence of methanogenic inhibitors chloroform, bromoethane sulfonate (BES), and methyl fluoride, which have different specificities. Methyl fluoride predominantly inhibits acetoclastic methanogenesis and affects hydrogenotrophic methanogenesis relatively little. Optimization of methyl fluoride concentrations resulted in complete inhibition of acetoclastic methanogenesis. Methane was then exclusively produced by hydrogenotrophic methanogenesis and thus allowed determination of the fractionation factors specific for this methanogenic pathway. Acetate, which was then no longer consumed, accumulated and allowed determination of the isotopic signatures of the fermentatively produced acetate. BES and chloroform also inhibited CH4 production and resulted in accumulation of acetate. The fractionation factor for hydrogenotrophic methanogenesis exhibited variability, e. g., it changed with sediment depth. The delta C-13 of the methyl group of the accumulated acetate was similar to the delta C-13 of sedimentary organic carbon, while that of the carboxyl group was by about 12 parts per thousand higher. However, the delta C-13 of the acetate was by about 5 parts per thousand lower in samples with uninhibited compared with inhibited acetoclastic methanogenesis, indicating unusual isotopic fractionation. The isotope data were used for calculation of the relative contribution of hydrogenotrophic vs. acetoclastic methanogenesis to total CH4 production. Contribution of hydrogenotrophic methanogenesis increased with sediment depth from about 35% to 60%, indicating that organic matter was only partially oxidized in deeper sediment layers.