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The Complexation Chemistry of Dissol...

Oldham, Veronique E.

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The Complexation Chemistry of Dissolved Manganese(III) in the Ocean And its Role in the Coupled Cycles of Carbon, Iron and Sulfur.

Record Type:	Electronic resources : Monograph/item
Title/Author:	The Complexation Chemistry of Dissolved Manganese(III) in the Ocean And its Role in the Coupled Cycles of Carbon, Iron and Sulfur./
Author:	Oldham, Veronique E.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2017,
Description:	234 p.
Notes:	Source: Dissertation Abstracts International, Volume: 79-02(E), Section: B.
Contained By:	Dissertation Abstracts International79-02B(E).
Subject:	Chemical oceanography. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10258361
ISBN:	9780355260328

The Complexation Chemistry of Dissolved Manganese(III) in the Ocean And its Role in the Coupled Cycles of Carbon, Iron and Sulfur.
Oldham, Veronique E.

The Complexation Chemistry of Dissolved Manganese(III) in the Ocean And its Role in the Coupled Cycles of Carbon, Iron and Sulfur. - Ann Arbor : ProQuest Dissertations & Theses, 2017 - 234 p.

Source: Dissertation Abstracts International, Volume: 79-02(E), Section: B.

Thesis (Ph.D.)--University of Delaware, 2017.

Manganese (Mn) speciation is dominated by dissolved Mn(II), Mn(III) and solid Mn(III/IV) oxides in seawater. Soluble Mn (dMnT) speciation has been re-evaluated in the last decade to include Mn(III)-L in low O 2 environments. The same ligands that bind iron(III) [Fe(III)] can also bind Mn(III). Therefore, in the marine environment, Mn(III) may have a profound impact on the bioavailability of dissolved Fe, which often requires organic complexation for uptake. In oxic waters, dMnT speciation is still thought to be dominated by dMn(II), and the presence of Mn(III)-L has not yet been assessed in oxic environments because of current detection limits for dMn speciation (50 nM).

ISBN: 9780355260328Subjects--Topical Terms:

516760
Chemical oceanography.

The Complexation Chemistry of Dissolved Manganese(III) in the Ocean And its Role in the Coupled Cycles of Carbon, Iron and Sulfur.
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100 1 $a Oldham, Veronique E. $3 3346510
245 1 4 $a The Complexation Chemistry of Dissolved Manganese(III) in the Ocean And its Role in the Coupled Cycles of Carbon, Iron and Sulfur.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2017
300 $a 234 p.
500 $a Source: Dissertation Abstracts International, Volume: 79-02(E), Section: B.
500 $a Adviser: George W. Luther.
502 $a Thesis (Ph.D.)--University of Delaware, 2017.
520 $a Manganese (Mn) speciation is dominated by dissolved Mn(II), Mn(III) and solid Mn(III/IV) oxides in seawater. Soluble Mn (dMnT) speciation has been re-evaluated in the last decade to include Mn(III)-L in low O 2 environments. The same ligands that bind iron(III) [Fe(III)] can also bind Mn(III). Therefore, in the marine environment, Mn(III) may have a profound impact on the bioavailability of dissolved Fe, which often requires organic complexation for uptake. In oxic waters, dMnT speciation is still thought to be dominated by dMn(II), and the presence of Mn(III)-L has not yet been assessed in oxic environments because of current detection limits for dMn speciation (50 nM).
520 $a Speciation assays were performed in contrasting redox environments: the Chesapeake Bay (seasonally anoxic bottom waters), the St. Lawrence Estuary (SLE) (air saturated O2 in surface waters, decreasing to 55 muM at the sediment-water interface), and a coastal waterway in Delaware, bordered by wetlands (air saturated O2 in surface waters). These systems provide unique O2 gradients to examine Mn biogeochemistry and its role in the cycles of C, Fe and S. I show that Mn(III)-L complexes are ubiquitous in the oxic marine environment (up to 99.9% of dMnT), much like their Fe(III)-L analogs, which dominate dFe speciation. I measured dMn speciation and Mn(III)-L conditional stability constants (Kcond), by competition with an added porphyrin ligand, where weak complexes are outcompeted by the added porphyrin (logKcond13.2).
520 $a In the Chesapeake Bay, I show that strong Mn(III)-L complexes make up to 80% of dMnT in areas of low/no oxygen, and in the presence of equimolar concentrations of a reducing agent, H2S. The reductive dissolution of MnOx produces Mn(III)-L in this system, and chemical reduction (by HS-) or ligand-promoted reduction may be responsible. In low O2 regimes, the stabilization of dMn(III) is favorable, thus, the increase in oxygen minimum zones due to changing climate regimes could lead to greater stabilization, cycling and transport of Mn(III)-L. I show that the suboxic portion of the water column in the Chesapeake Bay is an intense zone of Mn cycling, where Mn oxides can form at non-detectable dissolved O2 concentrations, and where Mn oxidizers and reducers may coexist.
520 $a I found that Mn(III)-L complexes made up to 99.9% of dMnT in the surface waters of the Broadkill River, DE and up to 86% in the SLE, indicating, for the first time, that Mn(III)-L complexes are also stable in oxygenated waters. In the SLE, dMn fluxed out of the sediments as dMn(II) (0.43 mmol m-2 day-1) and oxidation processes dominate Mn(III)-L production in the water column. The vertical profile of dMnT was 20-80% higher in the lower SLE than in 1974, corresponding to lower dO2 in the system. Here, dMnT was much higher in bottom waters (~2 microM), with Mn(III)-L stabilized 50 m above the sediment water interface (200 nM, 60% of dMnT). However, in the nearby Saguenay fjord, Mn(III)-L was not only entering via sediment flux and subsequent stabilization by ligands, but also through surface waters (60 nM Mn(III)-L, 65 % of dMn T), indicating that terrestrial ligands stabilize Mn(III).
520 $a Terrestrial-type ligands were also found to stabilize Mn(III)-L in the surface samples of dMn along a salinity gradient in the Broadkill River, a coastal waterway bordered by salt marshes. Here, high Mn(III)-L corresponded to high humic material, as indicated by characteristic UV absorption peaks. Additionally, an assay of ligand character was made after precipitating humic matter, and confirmed that Mn(III)-L complexes had ligands of humic character. Thus, humic material serves to bind Mn(III), which transports both Mn(III) and organic matter to the coastal ocean, indicating that estuarine export, rather than removal may be dominating these types of systems.
590 $a School code: 0060.
650 4 $a Chemical oceanography. $3 516760
690 $a 0403
710 2 $a University of Delaware. $b Marine Studies. $3 1270038
773 0 $t Dissertation Abstracts International $g 79-02B(E).
790 $a 0060
791 $a Ph.D.
792 $a 2017
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10258361