This study examines the chemical nature and reactivity of dissolved organic matter (DOM) in the anoxic, sedimentary, fresh water, pore waters of Old Woman Creek (OWC), located in Huron, OH.
Chapter 1 offers an introduction to DOM, and describes it general chemical makeup with respect to its source materials (terrestrial vs. microbial, allochthonous vs. autochthonous). More importantly, Chapter 1 explains the enormous role DOM plays in an ecosystem, with particular emphasis on DOM’s potential application in the realm of environmental remediation and rehabilitation.
Chapter 2 examines pore water DOM reactivity in the context of Cr(VI) remediation by Fe(II)-DOM complexes. Model and natural systems are used to examine differences in DOM reactivity and the feasibility of Cr(VI) in a wetland environment. Generally, DOM complexed to Fe(II) increased Cr(VI) reduction dramatically as compared to Fe(II)-only and microbially-mediated reduction. Additionally, microbially-derived vs. terrestrially-derived DOM exhibited differential reactivities as a function chemical make-up. We also observed a non-3:1 Fe(II): Cr(VI) reduction stoichiometry cyclical reduction of oxidized Fe(III) back to Fe(II) by DOM.
Chapter 3 employs a relatively new diagnostic tool known as Parallel Factor analysis (PARAFAC) to characterize pore water DOM in terms of mathematically modeled fluorescing constituents. In turn, these components represent chemically meaningful entities which may be used to explain pore water DOM reactivity. We identified three such components which are described as “humic-like”, “fulvic-like” and “protein”, “tryptophan”, “quinone-like” based upon comparison to existing PARAFAC models.
Chapter 4 characterizes pore water DOM using UV-VIS and fluorescence spectroscopy and existing correlations with 13C-NMR-determined aromaticity and the McKnight fluorescence index (a source material index). As a result OWC pore water DOM is identified as being both terrestrial and microbial in origin – which in turn explains its reactivity observed in Chapter 1. Chapter 5 presents a summary of the conclusions of Chapters 2-4.
Overall, the goal of this study is to supplement existing pore water studies to better understand the reactivity of DOM in natural systems, such as wetlands, especially in the context of contaminant remediation.