Abstract The marine sulphur cycle is driven by the reduction of sulphate to sulphide coupled to microbial decomposition of organic matter. The sulphide produced by sulphate reduction may either react with Fe or organic matter to be buried as pyrite or organic sulphur, respectively; or may be oxidised through different pathways and intermediates. The amount of sulphide that is oxidised in marine sediments is not well constrained, yet oxidative sulphur cycling has critical implications for hypoxic coastal waters and oxygen minimum zones, carbon mineralisation, microbial metabolism and the interpretation of ancient and modern stable isotope signatures. Here, we present an experimental method to directly determine sulphide oxidation rates in undiluted marine sediment incubations. We find that sulphide oxidation rates in the top two centimetres of organic-rich coastal sediments were greater than rates of sulphide production through sulphate reduction and calculate that in the top 6 centimetres, up to 92 % of sulphide produced during sulphate reduction was reoxidised. The rates decreased steeply with depth, however, and sulphide oxidation to sulphate could no longer be quantified 10 cm below the seafloor. Fe oxides were the primary oxidant for sulphide and the sulphide oxidation rate was related to the amount and reactivity of the Fe minerals. These results provide important insights into the magnitude and processes of the sulphur cycle in marine sediments.

中文翻译：

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海洋沉积物中硫化物氧化速率的量化

摘要 海洋硫循环是由硫酸盐还原为硫化物与微生物分解有机物共同驱动的。硫酸盐还原产生的硫化物可能与铁或有机物反应，分别以黄铁矿或有机硫的形式被掩埋；或可能通过不同的途径和中间体被氧化。海洋沉积物中被氧化的硫化物数量并没有得到很好的限制，但氧化硫循环对缺氧沿海水域和最低氧区、碳矿化、微生物代谢以及古代和现代稳定同位素特征的解释具有重要意义。在这里，我们提出了一种直接确定未稀释海洋沉积物孵化中硫化物氧化速率的实验方法。我们发现富含有机物的沿海沉积物顶部 2 厘米处的硫化物氧化速率大于通过硫酸盐还原产生的硫化物速率，并计算出在顶部 6 厘米处，硫酸盐还原过程中产生的硫化物高达 92% 被再氧化。然而，随着深度的增加，速率急剧下降，并且在海底 10 厘米处无法再量化硫化物氧化为硫酸盐的过程。Fe 氧化物是硫化物的主要氧化剂，硫化物氧化速率与 Fe 矿物的数量和反应性有关。这些结果为海洋沉积物中硫循环的大小和过程提供了重要的见解。硫酸盐还原过程中产生的硫化物高达 92% 被再氧化。然而，随着深度的增加，速率急剧下降，并且在海底 10 厘米处无法再量化硫化物氧化为硫酸盐的过程。Fe 氧化物是硫化物的主要氧化剂，硫化物氧化速率与 Fe 矿物的数量和反应性有关。这些结果为海洋沉积物中硫循环的大小和过程提供了重要的见解。硫酸盐还原过程中产生的硫化物高达 92% 被再氧化。然而，随着深度的增加，速率急剧下降，并且在海底 10 厘米处无法再量化硫化物氧化为硫酸盐的过程。Fe 氧化物是硫化物的主要氧化剂，硫化物氧化速率与 Fe 矿物的数量和反应性有关。这些结果为海洋沉积物中硫循环的大小和过程提供了重要的见解。