Redox and photochemical reactivity of dissolved organic matter in surface waters

A major objective of this research was to investigate the redox reactivity of dissolved organic matter (DOM) fluorophores in field and laboratory studies. Parallel factor analysis (PARAFAC), a statistical modeling approach, was used on a dataset of DOM excitation-emission matrices (EEMs) collected from diverse locations to identify the steady state fluorophores present in DOM. The spectral characteristics of the identified fluorophores as well as their reactivity upon microbial and electrochemical reduction were studied and compared to model quinones. Results suggest that about 50% of DOM fluorescence is due to redox active "quinone-like" moieties. In diverse surface waters, DOM fluorophores were found to shift consistently across redox gradients.; The subsequent objective of this thesis was to apply the new insight on DOM fluorophores to the photoreactivity of the DOM. It was found that fluorophores associated with microbially-derived organic matter are more photo-labile than terrestrially-derived DOM fluorophores. Further, the investigation of the photoreactivity of DOM fluorophores combined with traditional DOM characterization helped identify major controls on the chemical character of DOM across the Alaskan Arctic.