Geochemical evidence for cryptic sulfur cycling in salt marsh sediments
Geochemical evidence for cryptic sulfur cycling in salt marsh sediments
复制标题
DOI：
10.1016/j.epsl.2016.08.001
复制
发表时间：
2014-12
影响因子：
5.3
通讯作者：
J. Mills;G. Antler;A. Turchyn
中科院分区：
文献类型：
--
作者：
J. Mills;G. Antler;A. Turchyn
隐硫循环是一个神秘的过程，其中硫酸盐被还原为一些低价态硫物种，随后定量再氧化;该过程的速率和微生物能量学以及它在环境中的普遍程度仍然存在争议。在这里，我们调查了来自英国诺福克的盐沼沉积物中的硫循环，在那里我们观察到高亚铁浓度，硫酸盐没有耗尽或硫酸盐的硫同位素比的变化，但硫酸盐中的氧同位素比增加了5‰，表明硫酸盐已经通过还原循环取代其氧原子。这种神秘的硫循环在实验室培养中使用18 O-富集的水进行复制，表明现场结果并不仅仅是自然环境中混合过程的结果。数值模拟的实验室培养规模，以代表盐沼沉积物表明，硫酸盐的吸收速率在这个神秘的硫循环是类似的硫酸盐的吸收速率在最快的微生物硫酸盐还原，已在自然环境中测量。不同之处在于，在隐硫循环期间，所有硫随后被再氧化成硫酸盐。我们讨论的机制，这条途径的硫循环，包括可能的链接到地下铁循环。
Cryptic sulfur cycling is an enigmatic process in which sulfate is reduced to some lower-valence state sulfur species and subsequently quantitatively reoxidized; the rate and microbial energetics of this process and how prevalent it may be in the environment remain controversial. Here we investigate sulfur cycling in salt marsh sediments from Norfolk, England where we observe high ferrous iron concentrations with no depletion of sulfate or change in the sulfur isotope ratio of that sulfate, but a 5‰ increase in the oxygen isotope ratio in sulfate, indicating that sulfate has been through a reductive cycle replacing its oxygen atoms. This cryptic sulfur cycle was replicated in laboratory incubations using18O-enriched water, demonstrating that the field results do not solely result from mixing processes in the natural environment. Numerical modeling of the laboratory incubations scaled to represent the salt marsh sediments suggests that the uptake rate of sulfate during this cryptic sulfur cycling is similar to the uptake rate of sulfate during the fastest microbial sulfate reduction that has been measured in the natural environment. The difference is that during cryptic sulfur cycling, all of the sulfur is subsequently reoxidized to sulfate. We discuss mechanisms for this pathway of sulfur cycling including the possible link to the subsurface iron cycle.