Modeling vertical excursions of the redox boundary in sediments: Application to deep basins of the Arctic Ocean
Modeling vertical excursions of the redox boundary in sediments: Application to deep basins of the Arctic Ocean
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沉积物中氧化还原边界垂直偏移的模拟：在北冰洋深盆地的应用
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
A. Mucci
中科院分区：
文献类型：
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作者：
S. Katsev;B. Sundby;A. Mucci
成岩反应-输运模型用于模拟沉积物氧化还原边界如何响应可降解有机物沉积通量和上覆底水中氧浓度的持续或偶发变化而迁移。氧化还原边界的位置由氧渗透的深度表示。模拟表明，有机质贫乏沉积物（例如北冰洋深盆地的沉积物）中氧化还原边界的位置对有机质通量高度敏感：相对较小和/或短暂的通量增加可能会导致氧化还原边界从沉积物深处快速迁移到沉积物-水界面几厘米内。此类事件发生后沉积物柱的再氧化可能需要数年时间。氧化还原波动可以重新分布沉积物柱内的固相锰，并在十年时间尺度上在其深度剖面中产生多个浓度峰值。在北冰洋深海盆地沉积物岩心中观察到的锰峰不一定对应于先前气候时期氧化还原边界的位置，也不一定反映锰沉积速率的历史变化。该模型支持这样的假设：最近北极冰盖的减少增加了有机物到海底的通量，并使氧化还原边界移动到沉积物-水界面附近。在生物扰动层以下的深度存在硫化铁，这表明要么北极沉积物已经缺氧了数千年，要么这些深度的铁和硫酸盐因从生物扰动区向下扩散的溶解有机物而减少。
A diagenetic reaction‐transport model was used to simulate how the sediment redox boundary migrates in response to persistent or episodic changes in the deposition flux of degradable organic matter and the concentration of oxygen in the overlying bottom water. The position of the redox boundary is represented by the depth of oxygen penetration. The simulations reveal that the position of the redox boundary in organic‐poor sediments, such as those in the deep basins of the Arctic Ocean, is highly sensitive to the flux of organic matter: relatively small and/or brief increases in that flux can cause the redox boundary to migrate rapidly from deep within the sediment to within a few centimeters of the sediment‐water interface. Reoxidation of the sediment column after such an event can take years. Redox fluctuations can redistribute solid‐phase manganese within the sediment column and produce multiple concentration peaks in its depth profile on a decadal time scale. Manganese peaks observed in sediment cores from the deep basins of the Arctic Ocean do not necessarily correspond to the position of the redox boundary during previous climatic periods or reflect historical changes in manganese deposition rates. The model supports the hypothesis that the recent decrease in the Arctic ice cover has increased the flux of organic matter to the seafloor and moved the redox boundary close to the sediment‐water interface. The presence of iron sulfides at depths significantly below the bioturbated layer suggests that either the Arctic sediments have been anoxic for millennia, or iron and sulfate are reduced at these depths by dissolved organic matter diffusing downward from the bioturbation zone.