Isotopic variation of molecular hydrogen in 20°-375°C hydrothermal fluids as detected by a new analytical method
Isotopic variation of molecular hydrogen in 20°-375°C hydrothermal fluids as detected by a new analytical method
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DOI：
10.1029/2009jg001203
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发表时间：
2010-09
影响因子：
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通讯作者：
S. Kawagucci;T. Toki;J. Ishibashi;K. Takai;Michihiro Ito;T. Oomori;T. Gamo
中科院分区：
文献类型：
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作者：
S. Kawagucci;T. Toki;J. Ishibashi;K. Takai;Michihiro Ito;T. Oomori;T. Gamo
[1]分子氢（H2）是深海热液环境中化能自养微生物生态系统最重要的能源之一。本文研究了20°-375 ° C热液流体中H2的稳定同位素比值，以评价同位素比值作为示踪剂探索H2-代谢的有用性。在观测之前，我们开发了一种改进的分析方法，用于测定H2的浓度和稳定同位素比。该方法具有较高的灵敏度，检出限为1 nmol H_2，δ DH_2值的分析误差为10‰。高温流体的δ DH 2值在−405‰ ~ −330‰之间，表明在热液端元温度附近，H2和H2O之间达到了氢同位素平衡。与此相反，一些低温流体的δ DH 2值明显小于高温流体中的δ DH 2值，尽管由于流体-海水混合引起的δ DH 2变化可以忽略不计，这表明低温流体和周围环境中δ DH 2变化的可能性。由于低温环境中δ DH 2的变化不能很好地用H2和H2O之间非常缓慢的非生物热同位素平衡来解释，因此它可能与（微）生物消耗H2和/或产生H2的代谢有关，这些代谢将强烈促进低温下的同位素平衡。我们在深海热液系统中首次检测到δ DH 2的变化，表明δ DH 2值可作为微生物的新示踪剂，其酶催化H2中的D/H交换。
[1] Molecular hydrogen (H2) is one of the most important energy sources for subseafloor chemolithoautotrophic microbial ecosystems in the deep-sea hydrothermal environments. This study investigated stable isotope ratios of H2 in 20°–375°C hydrothermal fluids to evaluate usefulness of the isotope ratio as a tracer to explore the H2-metabolisms. Prior to the observation, we developed an improved analytical method for the determination of concentration and stable isotope ratio of H2. This method achieved a relatively high sensitivity with a detection limit of 1 nmol H2 within an analytical error of 10‰ in the δDH2 value. The δDH2 values in the high-temperature fluids were between −405‰ and −330‰, indicating the achievement of the hydrogen isotopic equilibrium between H2 and H2O at around the hydrothermal end-member temperature. In contrast, several low-temperature fluids showed apparently smaller δDH2 values than those in the high-temperature fluids in spite of a negligible δDH2 change due to fluid-seawater mixing, suggesting the possibility of δDH2 change in the low-temperature fluids and the surrounding environments. Since the δDH2 change in low-temperature environments is not well explained by the very sluggish abiotic thermal isotopic equilibrium between H2 and H2O, it could be associated with (micro)biological H2-consuming and/or H2-generating metabolisms that would strongly promote the isotopic equilibrium at low temperatures. Our first detection of the δDH2 variation in deep-sea hydrothermal systems presents the availability of the δDH2 value as a new tracer for microbes whose enzymes catalyze D/H exchange in H2.