One important environmental role of humic substances is their capacity as an electron acceptors and/or electron shuttles to ferric iron present as solid phase oxides. Evidence points to quinone-like moieties being the redox active moieties used by microbes in respiration. Concomitantly, the humic fraction contains the dominant fluorophores in many natural waters. There is similarity between the humic fluorophores and fluorescence spectra of model quinone compounds, with the more reduced species having red-shifted fluorescence spectra. Examination of spectra across redox gradients in aquatic systems shows that the spectra are also red-shifted under reducing conditions, such as anoxic bottom waters in lakes. This red-shift can be quantified based on the distribution of apparently oxidized quinone-like and more reduced, semi-quinone-like and hydroquinone-like fluorophores determined by PARAFAC. Because fluorescence spectroscopy can be applied at ambient DOM concentrations, fluorescence spectroscopy can provide insight into complex problems in environmental biogeochemistry.

Redox reactivity of humic substances in aquatic ecosystems: Multiple lines of evidence and the potential for understanding natural systems using fluorescence spectroscopy

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.