Sulfur and oxygen isotope study of sulfate reduction in experiments with natural populations from Faellestrand, Denmark
Sulfur and oxygen isotope study of sulfate reduction in experiments with natural populations from Faellestrand, Denmark
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DOI：
10.1016/j.gca.2008.03.013
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发表时间：
2008-06-15
影响因子：
5
通讯作者：
Johnston, David
中科院分区：
文献类型：
--
作者：
Farquhar, James;Canfield, Don E.;Johnston, David
本文研究了异化硫酸盐还原过程中硫、氧同位素的分馏，并试图调和氧、硫同位素与元素系统之间的关系。我们报告了对硫酸盐还原细菌自然种群的实验结果，实验使用了来自丹麦芬岛北岸Faellestrand海洋泻湖的沉积物和海水。实验得出了相对较大的硫同位素分馏，用于异化硫酸盐还原（S-34/S-32高达约45‰），较高的δ O-18伴随较高的δ S-34，与先前研究中观察到的相似。实验中使用的海水通过添加O-17标记的水进行加标，发现残留硫酸盐的O-17含量取决于实验中硫酸盐还原的分数。O-17数据提供了硫从代谢中间体中回收的证据，以及类似于异化硫酸盐还原的O-18/O-16分馏为25- 30ppm的证据。O-17数据与硫同位素数据的密切相关表明，在实验条件下，细胞水与外部水（反应堆水）之间的同位素交换是快速的。氧交换与硫酸盐还原的摩尔比约为2.5。这一数值略低于在自然生态系统研究中观察到的数值[例如，Wortmann U. G., Chernyavsky B., Bernasconi S. M., Brunner B., Bottcher M. E.和Swart P. K.（2007）深层生物圈孔隙水硫酸盐的氧同位素生物地球化学：微生物硫酸盐还原过程中与环境水的同位素交换反应的优势]（ODP Site 1130）。Geochim。Cosmochim。[j].中国科学：自然科学版。利用硫同位素分馏的最新模型，我们发现我们的硫和氧同位素组合数据限制了硫酸盐回收到介质中的比例（78-96%），硫中间体亚硫酸盐通过APS回收到硫酸盐并释放回外部硫酸盐池的比例（类似于70%），以及亚硫酸盐和硫化物之间的硫中间体的一部分被回收到硫酸盐。由于delta O-18、delta O-34、delta O-17标签和delta 33S提供的独立信息，这些参数可以受到约束。(c) 2008 Elsevier Ltd.版权所有。
This study investigates the sulfur and oxygen isotope fractionations of dissimilatory sulfate reduction and works to reconcile the relationships between the oxygen and sulfur isotopic and elemental systems. We report results of experiments with natural populations of sulfate-reducing bacteria using sediment and seawater from a marine lagoon at Faellestrand on the northern shore of the island of Fyn, Denmark. The experiments yielded relatively large magnitude sulfur isotope fractionations for dissimilatory sulfate reduction (up to approximately 45 parts per thousand for S-34/S-32) with higher delta O-18 accompanying higher delta S-34, similar to that observed in previous studies. The seawater used in the experiments was spiked by addition of O-17-labeled water and the O-17 content of residual sulfate was found to depend on the fraction of sulfate reduced in the experiments. The O-17 data provides evidence for recycling of sulfur from metabolic intermediates and for an O-18/O-16 fractionation of similar to 25-30 parts per thousand for dissimilatory sulfate reduction. The close correlation between the O-17 data and the sulfur isotope data suggests that isotopic exchange between cell water and external water (reactor water) was rapid under experimental conditions. The molar ratio of oxygen exchange to sulfate reduction was found to be about 2.5. This value is slightly lower than observed in studies of natural ecosystems [e.g., Wortmann U. G., Chernyavsky B., Bernasconi S. M., Brunner B., Bottcher M. E. and Swart P. K. (2007) Oxygen isotope biogeochemistry of pore water sulfate in the deep biosphere: dominance of isotope exchange reactions with ambient water during microbial sulfate reduction (ODP Site 1130). Geochim. Cosmochim. Acta 71, 4221-4232]. Using recent models of sulfur isotope fractionations we find that our combined sulfur and oxygen isotopic data places constraints on the proportion of sulfate recycled to the medium (78-96%), the proportion of sulfur intermediate sulfite that was recycled by way of APS to sulfate and released back to the external sulfate pool (similar to 70%), and also that a fraction of the sulfur intermediates between sulfite and sulfide were recycled to sulfate. These parameters can be constrained because of the independent information provided by delta O-18, delta O-34, delta O-17 labels, and Delta 33S. (c) 2008 Elsevier Ltd. All rights reserved.