峡湾
底栖区
海洋学
融水
地质学
焊剂(冶金)
沉积物
成岩作用
地质遗迹
沉积作用
沉积物捕集器
溶解二氧化硅
溶解
环境化学
矿物学
冰川
化学
水柱
地貌学
海水
物理化学
有机化学
作者
Hong Chin Ng,Jon R. Hawkings,Sebastien Bertrand,Brent A. Summers,Matthias Sieber,Tim M. Conway,Felipe S. Freitas,James P.J. Ward,Helena V. Pryer,Jemma L. Wadham,Sandra Arndt,Katharine R. Hendry
摘要
Glacier meltwater supplies silicon (Si) and iron (Fe) sourced from weathered bedrock to downstream ecosystems. However, the extent to which these nutrients reach the ocean is regulated by the nature of the benthic cycling of dissolved Si and Fe within fjord systems, given the rapid deposition of reactive particulate fractions at fjord heads. Here, we examine the benthic cycling of the two nutrients at four Patagonian fjord heads through geochemical analyses of sediment pore waters, including Si and Fe isotopes (δ30Si and δ56Fe), and reaction-transport modeling for Si. A high diffusive flux of dissolved Fe from the fjord sediments (up to 0.02 mmol m-2 day-1) compared to open ocean sediments (typically <0.001 mmol m-2 day-1) is supported by both reductive and non-reductive dissolution of glacially-sourced reactive Fe phases, as reflected by the range of pore water δ56Fe (-2.7 to +0.8‰). In contrast, the diffusive flux of dissolved Si from the fjord sediments (0.02–0.05 mmol m-2 day-1) is relatively low (typical ocean values are >0.1 mmol m-2 day-1). High pore water δ30Si (up to +3.3‰) observed near the Fe(II)-Fe(III) redox boundary is likely associated with the removal of dissolved Si by Fe(III) mineral phases, which, together with high sedimentation rates, contribute to the low diffusive flux of Si at the sampled sites. Our results suggest that early diagenesis promotes the release of dissolved Fe, yet suppresses the release of dissolved Si at glaciated fjord heads, which has significant implications for understanding the downstream transport of these nutrients along fjord systems.
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