Humic substances (HS) are important iron chelators responsible for the transport of iron from freshwater systems to the open sea, where iron is essential for marine organisms. Evidence suggests that iron complexed to HS comprises the bulk of the iron ligand pool in near‐coastal waters and shelf seas. River‐derived HS have been investigated to study their transport to, and dwell in oceanic waters. A library of iron model compounds and river‐derived Fe‐HS samples were probed in a combined X‐ray absorption spectroscopy (XAS) and valence‐to‐core X‐ray emission spectroscopy (VtC‐XES) study at the Fe K‐edge. The analyses performed revealed that iron complexation in HS samples is only dependent on oxygen‐containing HS functional groups, such as carboxyl and phenol. The photoreduction mechanism of FeIII‐HS in oceanic conditions into bioavailable aquatic FeII forms, highlights the importance of river‐derived HS as an iron source for marine organisms. Consequently, such mechanisms are a vital component of the upper‐ocean iron biogeochemistry cycle.
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机译:腐殖质(HS)是重要的铁螯合剂,负责将铁从淡水系统运输到公海,在公海中铁对于海洋生物至关重要。有证据表明,与HS络合的铁占近岸水域和架子海中铁配体池的大部分。已对源自河流的HS进行了研究,以研究它们向海洋水域的运输和栖息情况。在Fe K-edge的组合X射线吸收光谱(XAS)和价芯X射线发射光谱(VtC-XES)研究中探查了铁模型化合物和河源Fe-HS样品库。进行的分析表明,HS样品中的铁络合仅取决于含氧的HS官能团,例如羧基和苯酚。 Fe III sup> -HS在海洋条件下光还原为可生物利用的水生Fe II sup>形式的机理,突显了河流来源的HS作为海洋生物铁源的重要性。因此,这些机制是上层铁生物地球化学循环的重要组成部分。
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