Date of Award

2016

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

College of Arts and Sciences

First Advisor

John Ferry

Abstract

The oxic portion of the biosphere is a metastable mixture of different oxidation states of carbon, sulfur and oxygen energetically poised from equilibrium by the net rate differentials between photosynthetic carbon fixation and its metabolic or abiotic oxidation. The direct reaction of dioxygen with reduced carbon or sulfur is spin forbidden and therefore kinetically slow, but ferric and ferrous iron species serve as catalysts for enabling their oxidation and therefore play critical roles in the environment. This thesis reports exploratory and hypothesis driven research that seeks a better understanding of the physical and chemical limitations on the effectiveness of iron to catalyze interaction between the different oxidation states of these elements. These include studies of the relationship between iron speciation and its ability to generate reactive oxygen species (Chapter 1); the role of heterogeneous iron oxide suspensions in controlling reactive oxygen species yield during the spontaneous reaction of Fe(II) and O2 (Chapter 2), an exploration of the system of natural iron-containing soils, sulfide and oxygen and how they produce superoxide and hydrogen peroxide (Chapter 3) and a preliminary report of reactive oxygen species and antioxidant enzyme formation in the salt marsh muds (Chapter 4). The results are showing that ferric iron catalyzed oxidation of hydrogen sulfide is an important reservoir for the generation of reactive oxygen species except for the photoinduced processes. The ferrous iron oxidation in the presence of ferric oxides shows a faster oxidation rate and produces a higher yield of reactive oxygen species, which is indicating the catalysis of the process by removing ferric species from the iron cycle.

Rights

© 2016, Shengnan Meng

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