CHEMICAL CONTROLS ON THE BIOTIC AND ABIOTIC RELEASE OF CHROMIUM AND VANADIUM
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Date
2024-03-25
Authors
Balogun, Fatai
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Contamination of ground and well water by Cr and V from anthropogenic and geogenic sources has gained considerable attention over the last few decades due to environmental and public health concerns. The specific threat of Cr and V contamination is dictated by their redox speciation. In the natural environment, redox active phases such as ubiquitous Iron and manganese (oxyhydr)oxides are known to modulate mechanisms responsible for the mobility and bioavailability of Cr and V. Also, Cr and V availability is dependent on the reactivity of natural organic matter, which may serve as a major reductant of oxidized species, sorbent, and facilitator of mineral dissolution. Despite this knowledge, the specific constraints on the mechanisms of Cr and V oxidation, release, and retention by different organic carbon types, Fe and, Mn(oxyhydr)oxides in model and natural systems are not well understood. Accordingly, the objectives of this work were to (1) gain a more detailed mechanistic understanding of how organic carbon proxies and Mn-oxide influence Cr oxidation and release; (2) determine the host phases for Cr and V in aquifer materials and quantify their adsorption capacities; (3) determine the impact of organic matter and Mn-oxide proxies on the biotic and abiotic release of Cr and V in aquifer materials. Our experiments showed that aliphatic citric acid produced 8.5 times less Cr(VI) than aromatic gallic acid. In chemically variable saprolites, the affinity for V was 8 – 11 times greater than for Cr. Amorphous phases were inferred to be the major host phases for Cr and V. Lastly, organic carbon abiotically released Cr and V from solid host phases, while Mn-oxide influenced the release of Cr and V only in Redlair saprolite. This work underscores the need to integrate organic carbon types and mineralogical controls into predictive models for redox-sensitive metal dynamics and environmental availability.
This dissertation includes previously published and unpublished coauthored material.
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Keywords
Chromium oxidation, Incubation, Manganese oxide, Organic acids, Spectroscopy, Vanadium