TY - JOUR
T1 - Distribution of desferrioxamine-B-extractable soluble manganese(III) and particulate MnO 2 in the St. Lawrence Estuary, Canada
AU - Jones, Matthew R.
AU - Oldham, Véronique E.
AU - Luther, George W.
AU - Mucci, Alfonso
AU - Tebo, Bradley M.
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. We are also grateful to the captain and crew of the R/V Coriolis II for their hospitality as well as Gilles Desmeules for his help in acquiring water and sediment samples for this research.
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2019/1/20
Y1 - 2019/1/20
N2 - Soluble organically-complexed manganese(III) (Mn(III)-L) is an intermediate species in the manganese cycle. The reactivity of the complex(es) depends on the abundance and nature of the ligand(s), as well as its physicochemical environment. Currently, the strength of Mn(III)-L complexes is assessed by their ability to react either directly with a porphyrin complex, using the kinetics of its competitive ligand exchange reactions, or after being reduced to manganese(II). We present a new three-step technique that quantifies part of the Mn(III)-L pool which may represent a bioavailable and reactive fraction of the complexes. This technique relies on 1) ligand exchange of the dissolved complexes in a filtered field sample with the siderophore desferrioxamine-B (DFOB), 2) chromatographic separation and concentration of manganese(III)-DFOB from the aqueous matrix, and 3) quantification of the naturally ligated manganese(III) that was outcompeted by DFOB (Mn(III)-L DFOB ) at low concentrations by flow injection UV-Vis spectrophotometry. The formation of an extractable Mn(III)-L DFOB complex provides an operationally-defined benchmark by which to assess biological interactions and better understand the cycling of manganese(III) in the environment. The technique, with a detection limit of 0.09 nM, was applied to water samples collected in the St. Lawrence Estuary (SLE) and adjacent Saguenay Fjord in Canada. Mn(III)-L DFOB was ubiquitous at our study sites, but its concentration was low relative to total dissolved manganese (dMn T ) and particulate MnO 2 . Spatial variations of the dMn T speciation within the Saguenay Fjord suggest that Mn(III)-L forms from the reduction of MnO 2 . Likewise, variations of the dMn T speciation along a dissolved oxygen gradient in the SLE leads us to believe that Mn(III)-L DFOB likely represents a fraction of the total Mn(III)-L that cycles more readily in estuarine and marine systems.
AB - Soluble organically-complexed manganese(III) (Mn(III)-L) is an intermediate species in the manganese cycle. The reactivity of the complex(es) depends on the abundance and nature of the ligand(s), as well as its physicochemical environment. Currently, the strength of Mn(III)-L complexes is assessed by their ability to react either directly with a porphyrin complex, using the kinetics of its competitive ligand exchange reactions, or after being reduced to manganese(II). We present a new three-step technique that quantifies part of the Mn(III)-L pool which may represent a bioavailable and reactive fraction of the complexes. This technique relies on 1) ligand exchange of the dissolved complexes in a filtered field sample with the siderophore desferrioxamine-B (DFOB), 2) chromatographic separation and concentration of manganese(III)-DFOB from the aqueous matrix, and 3) quantification of the naturally ligated manganese(III) that was outcompeted by DFOB (Mn(III)-L DFOB ) at low concentrations by flow injection UV-Vis spectrophotometry. The formation of an extractable Mn(III)-L DFOB complex provides an operationally-defined benchmark by which to assess biological interactions and better understand the cycling of manganese(III) in the environment. The technique, with a detection limit of 0.09 nM, was applied to water samples collected in the St. Lawrence Estuary (SLE) and adjacent Saguenay Fjord in Canada. Mn(III)-L DFOB was ubiquitous at our study sites, but its concentration was low relative to total dissolved manganese (dMn T ) and particulate MnO 2 . Spatial variations of the dMn T speciation within the Saguenay Fjord suggest that Mn(III)-L forms from the reduction of MnO 2 . Likewise, variations of the dMn T speciation along a dissolved oxygen gradient in the SLE leads us to believe that Mn(III)-L DFOB likely represents a fraction of the total Mn(III)-L that cycles more readily in estuarine and marine systems.
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U2 - 10.1016/j.marchem.2018.11.005
DO - 10.1016/j.marchem.2018.11.005
M3 - Article
AN - SCOPUS:85057440532
SN - 0304-4203
VL - 208
SP - 70
EP - 82
JO - Marine Chemistry
JF - Marine Chemistry
ER -