Glacial influence on the iron and sulfur cycles in Arctic fjord sediments (Svalbard)
Glacial influence on the iron and sulfur cycles in Arctic fjord sediments (Svalbard)
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DOI：
10.1016/j.gca.2019.12.033
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发表时间：
2020-07-01
影响因子：
5
通讯作者：
Jorgensen, Bo Barker
中科院分区：
文献类型：
--
作者：
Michaud, Alexander B.;Laufer, Katja;Jorgensen, Bo Barker
斯瓦尔巴特群岛的北极峡湾沉积物接受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。北极高地冰川的持续退缩正在改变峡湾的冰川物质输入，对峡湾沉积物中的铁和硫循环产生未知的影响。我们测量了沉积物岩心中的硫酸盐还原速率，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育进行比较，以确定斯瓦尔巴群岛斯匹次卑尔根群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。尽管丰富的冰川来源的Fe（III）-氧化物矿物，活性硫酸盐还原发生在整个沉积物。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，从生物硫酸盐还原产生的硫化物被再氧化为硫酸盐。长期的沉积物培养表明，在所有三个站的硫化物氧化。硫化物氧化的速率由硫酸盐还原的速率和Fe（III）氧化物的数量和反应性控制。在我们的实验孵育中，我们检测到Fe（III）含量的0.5 M HCl和抗坏血酸可提取馏分的减少，但不是在6 M HCl馏分，表明高反应性的Fe（III）馏分被微生物利用，并作为硫化物氧化的氧化剂。我们的研究结果表明，在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。进一步的变暖将促使冰川退缩到陆地上，在那里，充满沉积物的冰川融水在流入海洋环境之前，将在流经冰前河流和湖泊的过程中发生变化。峡湾沉积物可能会变得更加硫化物，因为冰川向海洋环境提供更少的颗粒，高活性金属氧化物。(C)2020爱思唯尔有限公司保留所有权利。
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 pore-water 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. (C) 2020 Elsevier Ltd. All rights reserved.