Photoreduction of Terrigenous Fe-Humic Substances Leads to Bioavailable Iron in Oceans.
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 Fe(III) -HS in oceanic conditions into bioavailable aquatic Fe(II) 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.
Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090, Vienna, Austria.
Amir
A
Blazevic
Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 42, 1090, Vienna, Austria.
Ewelina
E
Orlowska
Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 42, 1090, Vienna, Austria.
Wolfgang
W
Kandioller
Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Althanstraße 14, 1090, Vienna, Austria.
Franz
F
Jirsa
Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 42, 1090, Vienna, Austria.
Bernhard K
BK
Keppler
Institut für Angewandte Synthesechemie, Technische Universität Wien, Getreidemarkt 9/163-AC, 1060, Vienna, Austria.
Myrvete
M
Tafili-Kryeziu
Institut für Angewandte Synthesechemie, Technische Universität Wien, Getreidemarkt 9/163-AC, 1060, Vienna, Austria.
Wolfgang
W
Linert
Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Althanstraße 14, 1090, Vienna, Austria.
Rudolf F
RF
Krachler
Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Althanstraße 14, 1090, Vienna, Austria.
Regina
R
Krachler
Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090, Vienna, Austria. annette.rompel@univie.ac.at.
Annette
0000-0002-5919-0553
A
Rompel
D006812:Humic Substances; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D055668:Photochemical Processes
D006812:Humic Substances; D007501:Iron
Fe K-edge; complexed iron; dissolved organic matter; iron chelator agents; natural organic matter