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Geochemistry of manganese and iron a...

Trouwborst, Robert Elisa.

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Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones./
作者:	Trouwborst, Robert Elisa.
面頁冊數:	177 p.
附註:	Source: Dissertation Abstracts International, Volume: 66-12, Section: B, page: 6492.
Contained By:	Dissertation Abstracts International66-12B.
標題:	Geochemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3200548
ISBN:	9780542458132

Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones.
Trouwborst, Robert Elisa.

Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones. - 177 p.

Source: Dissertation Abstracts International, Volume: 66-12, Section: B, page: 6492.

Thesis (Ph.D.)--University of Delaware, 2006.

Manganese stabilizes suboxic regions by a vigorous cycle of oxidation and reduction reactions. During oxidation of Mn2+ to Mn(IV), the intermediate Mn(III) is formed, which can be stabilized by available complexing ligands. Since the presence of dissolved Mn(III) complexes in the marine environment was never investigated, their role in suboxic water was unknown. An electrochemical method was developed to analyze dissolved Mn(III) complexes in the marine environment and was applied to investigate the stable suboxic zone of the Black Sea and the dynamic suboxic region of the Chesapeake Bay for Mn(III) complexes. Mn(III) showed a maximum in the suboxic zone of the Black Sea and Chesapeake Bay, but was not observed in the oxic and sulfidic zones of the water column. Soluble Mn(III) formed a significant fraction (up to 100% in the Black Sea) of total soluble manganese. These high dissolved Mn(III) concentrations were found near the Bosporus inlet and were associated with oxygen-rich injections. The presence of Mn(III) indicates that it might facilitate upward transfer of electrons from hydrogen sulfide to oxygen and so stabilize the suboxic zone.

ISBN: 9780542458132Subjects--Topical Terms:

539092
Geochemistry.

Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones.
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245 1 0 $a Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones.
300 $a 177 p.
500 $a Source: Dissertation Abstracts International, Volume: 66-12, Section: B, page: 6492.
500 $a Adviser: George W. Luther.
502 $a Thesis (Ph.D.)--University of Delaware, 2006.
520 $a Manganese stabilizes suboxic regions by a vigorous cycle of oxidation and reduction reactions. During oxidation of Mn2+ to Mn(IV), the intermediate Mn(III) is formed, which can be stabilized by available complexing ligands. Since the presence of dissolved Mn(III) complexes in the marine environment was never investigated, their role in suboxic water was unknown. An electrochemical method was developed to analyze dissolved Mn(III) complexes in the marine environment and was applied to investigate the stable suboxic zone of the Black Sea and the dynamic suboxic region of the Chesapeake Bay for Mn(III) complexes. Mn(III) showed a maximum in the suboxic zone of the Black Sea and Chesapeake Bay, but was not observed in the oxic and sulfidic zones of the water column. Soluble Mn(III) formed a significant fraction (up to 100% in the Black Sea) of total soluble manganese. These high dissolved Mn(III) concentrations were found near the Bosporus inlet and were associated with oxygen-rich injections. The presence of Mn(III) indicates that it might facilitate upward transfer of electrons from hydrogen sulfide to oxygen and so stabilize the suboxic zone.
520 $a Early photosynthetic organisms are assumed to have played a major role in the formation of Precambrian Banded Iron Formations (BIFs) by either oxidizing iron directly or by producing oxygen during photosynthesis, which in turn oxidized the iron. Microbial mats at Chocolate Pots Hot Springs in Yellowstone National Park composed of oxygenic cyanobacteria and the anoxygenic phototroph Chloroflexus were studied as a model to discriminate the role of either process. Voltammetric microelectrodes were used to measure dissolved oxygen, manganese and iron simultaneously in situ with a 0.05 mm depth resolution. Oxygenic photosynthesis produced enough oxygen to remove all iron (II) from the mat at light intensities >85 W/m2. Incubation and in situ experiments indicated that direct iron oxidation facilitated by anoxygenic photosynthesis could produce at maximum 10% of the total iron oxidation. The Fe(II) oxidation rates caused by oxygenic photosynthesis measured in this study are sufficient to explain BIF formation.
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