TY - JOUR
T1 - Soluble Mn(III)–L complexes are abundant in oxygenated waters and stabilized by humic ligands
AU - Oldham, Véronique E.
AU - Mucci, Alfonso
AU - Tebo, Bradley M.
AU - Luther, George W.
N1 - Funding Information:
This work was funded by grants from the Chemical Oceanography program of the National Science Foundation (OCE-1558738 and OCE-1155385 to GWL; OCE-1558692 and OCE-1154307 to BMT) and the National Sciences and Engineering Research Council of Canada (NSERC) through Discovery and Ship-time grants to AM. Véronique Oldham thanks the University of Delaware for receipt of a Marian R. Okie Fellowship and a University of Delaware Graduate Fellowship. Thanks also to the crew of the R/V Coriolis II who made sampling for this research possible, and Matthew R. Jones who carried out the MnO
Publisher Copyright:
© 2016 Elsevier Ltd
PY - 2017/2/15
Y1 - 2017/2/15
N2 - Dissolved Mn (dMnT) is thought to be dominated by metastable Mn(II) in the presence of oxygen, as the stable form is insoluble Mn(IV). We show, for the first time, that Mn(III) is also stable as a soluble species in the oxygenated water column, when stabilized by organic ligands as Mn(III)–L complexes. We measured Mn(III)–L complexes in the oxygenated waters of a coastal fjord and a hemipelagic system where they make up to 86% of the dMnT. Although Mn(III) forms similar complexes to Fe(III), unlike most of the analogous Fe(III)–L complexes, the Mn(III)–L complexes are not colloidal, as they pass through both 0.20 μm and 0.02 μm filters. Depending on the kinetic stability of the Mn(III) complexes and the microbial community of a given system, these Mn(III)–L complexes are capable of donating or accepting electrons and may therefore serve as both reductants or oxidants, can be biologically available, and can thus participate in a multitude of redox reactions and biogeochemical processes. Furthermore, sample acidification experiments revealed that Mn(III) binding to humic ligands is responsible for up to 100% of this complexation, which can influence the formation of other metal complexes including Fe(III) and thus impact nutrient availability and uptake. Hence, humic ligands may play a greater role in dissolved Mn transport from coastal areas to the ocean than previously thought.
AB - Dissolved Mn (dMnT) is thought to be dominated by metastable Mn(II) in the presence of oxygen, as the stable form is insoluble Mn(IV). We show, for the first time, that Mn(III) is also stable as a soluble species in the oxygenated water column, when stabilized by organic ligands as Mn(III)–L complexes. We measured Mn(III)–L complexes in the oxygenated waters of a coastal fjord and a hemipelagic system where they make up to 86% of the dMnT. Although Mn(III) forms similar complexes to Fe(III), unlike most of the analogous Fe(III)–L complexes, the Mn(III)–L complexes are not colloidal, as they pass through both 0.20 μm and 0.02 μm filters. Depending on the kinetic stability of the Mn(III) complexes and the microbial community of a given system, these Mn(III)–L complexes are capable of donating or accepting electrons and may therefore serve as both reductants or oxidants, can be biologically available, and can thus participate in a multitude of redox reactions and biogeochemical processes. Furthermore, sample acidification experiments revealed that Mn(III) binding to humic ligands is responsible for up to 100% of this complexation, which can influence the formation of other metal complexes including Fe(III) and thus impact nutrient availability and uptake. Hence, humic ligands may play a greater role in dissolved Mn transport from coastal areas to the ocean than previously thought.
KW - Humic Material
KW - Manganese
KW - Mn(III)-L
KW - Organic Complexation
KW - Redox Chemistry
KW - Speciation
KW - St. Lawrence Estuary
KW - Trace Metal
KW - Water Column
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U2 - 10.1016/j.gca.2016.11.043
DO - 10.1016/j.gca.2016.11.043
M3 - Article
AN - SCOPUS:85006963749
VL - 199
SP - 238
EP - 246
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
SN - 0016-7037
ER -