Author

Fan Wang

Date of Award

Summer 2020

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

John L. Ferry

Abstract

Hydrogen peroxide is a reduced form of dioxygen produced in natural waters from a manifold of abiotic and biological processes. Hydrogen peroxide is highly redox active and it often serves to initiate the formation of reactive oxygen species in the environment. It typically exists in natural waters at concentrations ranging from as low as ~ 1 nanomolar in “blue water” marine environments to as high as 10 micromolar near actively effluxing sediments. It has the potential to cause significant toxicity in aquatic organisms, which have evolved a collection of antioxidant enzymes including peroxidase, catalase, and superoxide dismutase. Work in this thesis is focused on the interaction of hydrogen peroxide and the peroxidase enzyme at redox interfaces, including the sediment/water column interface, saturated and unsaturated vadose zone, and pseudointerface in dense cyanobacterial communities. Initial field work shown documents the importance of oxic/anoxic interfaces at sediment surfaces as abiotic factors that force enhanced formation of peroxidases relative to total biomass in the system. This is shown in a detailed characterization of a field site disturbed by the storm surge of a passing hurricane; a “pump and probe” experiment that briefly transformed a salt marsh dominated by tidal water movement to a continuously submerged environment. The effect of such disruptions was further explored by examining the effect of naturally occurring levels of peroxide and peroxidase on anthropogenic contaminants in the presence of varying salinity and varying levels of biogenic dissolved organic carbon. At concentrations of peroxide and peroxidase representative of those in natural soils model contaminants were effectively condensed to high molecular weight, insoluble polymers. Resulting immobilization was explored further at higher concentrations of the two species to explore their potential as remediation agents for the purposeful removal of organic contaminants in groundwater. Although increasing salinity, corresponding to the coastal flooding described in the earlier field work, had little effect on net removal the addition of biogenic natural carbon, it had statistically significant and positive effects on contaminant removal. Work in the thesis also examined the role of dense cyanobacterial mats, separate from sediments, in promoting the formation of peroxide and peroxidases. Field examination of the harmful algal bloom Microseira wollei showed no peroxide but high levels of a novel peroxidase; sufficient levels to account for the difficulty in peroxide detection. The mats were characterized for peroxidase content and it was determined that sufficient peroxidase was present to afford the cyanobacteria a plausible defense mechanism for exogenous peroxycarbonate that is often applied as an algaecide for Microseira species and other harmful algal blooms. Microseira wollei peroxidase was also evaluated for its ability to affect organic contaminants, including some algaecidal agents.

Available for download on Monday, August 15, 2022

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