BACKGROUND We studied the annual variability of the concentration and isotopic composition of main sulfur species and sulfide oxidation intermediates in the water column of monomictic fresh-water Lake Kinneret. Sulfate concentrations in the lake are <1 mM and similar to concentrations that are proposed to have existed in the Paleoproterozoic ocean. The main goal of this research was to explore biogeochemical constrains of sulfur cycling in the modern low-sulfate fresh-water lake and to identify which processes may be responsible for the isotopic composition of sulfur species in the Precambrian sedimentary rocks. RESULTS At the deepest point of the lake, the sulfate inventory decreases by more than 20% between March and December due to microbial sulfate reduction leading to the buildup of hydrogen sulfide. During the initial stages of stratification, sulfur isotope fractionation between sulfate and hydrogen sulfide is low (11.6 ‰) and sulfur oxyanions (e.g. thiosulfate and sulfite) are the main products of the incomplete oxidation of hydrogen sulfide. During the stratification and at the beginning of the lake mixing (July-December), the inventory of hydrogen sulfide as well as of sulfide oxidation intermediates in the water column increases and is accompanied by an increase in sulfur isotope fractionation to 30 ± 4 ‰ in October. During the period of erosion of the chemocline, zero-valent sulfur prevails over sulfur oxyanions. In the terminal period of the mixing of the water column (January), the concentration of hydrogen sulfide decreases, the inventory of sulfide oxidation intermediates increases, and sulfur isotope fractionation decreases to 20 ± 2 ‰. CONCLUSIONS Sulfide oxidation intermediates are present in the water column of Lake Kinneret at all stages of stratification with significant increase during the mixing of the water column. Hydrogen sulfide inventory in the water column increases from March to December, and sharply decreases during the lake mixis in January. Sulfur isotope fractionation between sulfate and hydrogen sulfide as well as concentrations of sulfide oxidation intermediates can be explained either by microbial sulfate reduction alone or by microbial sulfate reduction combined with microbial disproportionation of sulfide oxidation intermediates. Our study of sulfur cycle in Lake Kinneret may be useful for understanding the range of biogeochemical processes in low sulfate oceans over Earth history.

中文翻译：

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亚硫酸盐浓度低于一毫摩尔的温暖单晶湖泊中的年度硫循环。

背景技术我们研究了单分子淡水Kinneret湖水柱中主要硫物种和硫化物氧化中间体的浓度和同位素组成的年度变化。湖泊中的硫酸盐浓度<1 mM，与拟古生代海洋中存在的浓度相似。这项研究的主要目的是探索现代低硫酸盐淡水湖中硫循环的生物地球化学约束，并确定哪些过程可能是前寒武纪沉积岩中硫物种同位素组成的原因。结果在该湖的最深处，由于微生物硫酸盐的减少导致硫化氢的积累，硫酸盐库存在3月至12月之间减少了20％以上。在分层的初始阶段，硫酸盐和硫化氢之间的硫同位素分馏率低（11.6‰），硫氧阴离子（例如硫代硫酸盐和亚硫酸盐）是硫化氢不完全氧化的主要产物。在分层过程中和湖泊混合开始时（7月至12月），水柱中硫化氢以及硫化物氧化中间体的存量增加，并伴随着硫同位素分馏增加到30±4‰。十月。在趋化环的腐蚀期间，零价硫比硫氧阴离子占优势。在水塔混合的末期（一月），硫化氢的浓度降低，硫化物氧化中间体的存量增加，硫同位素分馏降低到20±2‰。结论肯纳雷特湖水柱在分层的所有阶段都存在硫化物氧化中间体，并且在水柱混合过程中有明显的增加。从3月到12月，水柱中的硫化氢存量增加，而在一月​​份的湖中则急剧减少。硫酸盐和硫化氢之间的硫同位素分馏以及硫化物氧化中间体的浓度可以通过单独的微生物硫酸盐还原或通过微生物硫酸盐还原与硫化物氧化中间体的微生物歧化结合来解释。我们对Kinneret湖中硫循环的研究可能有助于了解地球历史上低硫酸盐海洋中生物地球化学过程的范围。结论在Kinneret湖的分层过程的所有阶段中，硫化物氧化中间体都存在于Kinneret湖的水柱中，并且在水柱混合过程中有明显的增加。水柱中的硫化氢库存量从3月到12月增加，而在1月的湖中则急剧减少。硫酸盐和硫化氢之间的硫同位素分馏以及硫化物氧化中间体的浓度可以通过单独的微生物硫酸盐还原或通过微生物硫酸盐还原与硫化物氧化中间体的微生物歧化结合来解释。我们对Kinneret湖中硫循环的研究可能有助于了解地球历史上低硫酸盐海洋中生物地球化学过程的范围。结论肯纳雷特湖水柱在分层的所有阶段都存在硫化物氧化中间体，并且在水柱混合过程中有明显的增加。水柱中的硫化氢库存量从3月到12月增加，而在1月的湖中则急剧减少。硫酸盐和硫化氢之间的硫同位素分馏以及硫化物氧化中间体的浓度可以通过单独的微生物硫酸盐还原或通过微生物硫酸盐还原与硫化物氧化中间体的微生物歧化结合来解释。我们对Kinneret湖中硫循环的研究可能有助于了解地球历史上低硫酸盐海洋中生物地球化学过程的范围。