Abstract Arctic fjord sediments of Svalbard receive terrestrial material from glacial runoff and organic matter from marine primary productivity. Organic carbon mineralization proceeds primarily through sulfate and iron reduction in the fjord sediment. The ongoing retreat of glaciers in the high Arctic is altering the input of glacial material to the fjords, with unknown consequences for the iron and sulfur cycles in the fjord sediments. We measured sulfate reduction rates in sediment cores and analyzed porewater geochemistry, then compared these results to long-term sediment incubations to determine the rates of iron reduction and sulfide oxidation in three glacially influenced fjords on the west coast of Spitsbergen, Svalbard. Despite an abundance of glacially-sourced Fe(III)-oxide minerals, active sulfate reduction took place throughout the sediment. Analyses of the sulfur and oxygen isotopic composition of porewater sulfate and sulfate concentrations suggest that sulfide produced from biological sulfate reduction is reoxidized to sulfate. Long-term sediment incubations indicated sulfide oxidation at all three stations. The rate of sulfide oxidation was controlled by both the rate of sulfate reduction and the quantity and reactivity of Fe(III)-oxides. In our experimental incubations, we detected a decrease in Fe(III) content of the 0.5 M HCl and ascorbate-extractable fractions, but not in the 6 M HCl fraction, indicating that the highly reactive Fe(III) fraction is utilized by microorganisms and serves as the oxidant for sulfide oxidation. Our results show that sulfide oxidation in glacially-influenced fjord sediments is a wide-spread geochemical process. Further warming will drive glacial retreat onto land, where sediment-laden glacial meltwater will be altered during flow through proglacial streams and lakes before entering the marine environment. Fjord sediments will likely become more sulfidic, as glaciers deliver less particulate, highly-reactive metal oxides to the marine environment.

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冰川对北极峡湾沉积物（斯瓦尔巴群岛）中铁和硫循环的影响

摘要 斯瓦尔巴群岛的北极峡湾沉积物接收来自冰川径流的陆地物质和来自海洋初级生产力的有机物质。有机碳矿化主要通过峡湾沉积物中的硫酸盐和铁还原进行。北极地区冰川的持续退缩正在改变冰川物质向峡湾的输入，对峡湾沉积物中的铁和硫循环产生未知的影响。我们测量了沉积物核心中硫酸盐还原率并分析了孔隙水地球化学，然后将这些结果与长期沉积物孵化进行了比较，以确定斯瓦尔巴群岛斯匹次卑尔根岛西海岸三个受冰川影响的峡湾中铁还原和硫化物氧化的速率。尽管有丰富的冰川来源的 Fe(III)-氧化物矿物，整个沉积物中都发生了活性硫酸盐还原。对孔隙水硫酸盐和硫酸盐浓度的硫和氧同位素组成的分析表明，生物硫酸盐还原产生的硫化物被重新氧化为硫酸盐。长期沉积物孵化表明所有三个站点都发生了硫化物氧化。硫化物氧化速率受硫酸盐还原速率和 Fe(III)-氧化物的数量和反应性控制。在我们的实验培养中，我们检测到 0.5 M HCl 和抗坏血酸可提取部分的 Fe(III) 含量降低，但 6 M HCl 部分没有，这表明高反应性 Fe(III) 部分被微生物和用作硫化物氧化的氧化剂。我们的研究结果表明，受冰川影响的峡湾沉积物中的硫化物氧化是一个广泛的地球化学过程。进一步变暖将推动冰川退缩到陆地上，在进入海洋环境之前，富含沉积物的冰川融水在流经前冰河和湖泊时会发生变化。峡湾沉积物可能会变得更加硫化，因为冰川向海洋环境输送的颗粒状、高反应性金属氧化物较少。