Photochemical reactions involving dissolved organic matter (DOM) yield a suite of photochemically produced reactive intermediates (PPRI). These species affect contaminant fate in aquatic environments and participate in reactions involving the flux between dissolved and atmospheric carbon. To investigate relationships between DOM composition and mechanisms for PPRI formation, we combine extensive water sampling with detailed DOM characterization and evaluation of photoreactivity. We sampled oligotrophic, mesotrophic, and eutrophic lakes, dystrophic bogs, rivers and streams impacted by agricultural runoff and wastewater effluent, and waters in highly urbanized watersheds. DOM characterization includes molecular analysis using Fourier-transform ion cyclotron resonance mass spectrometry and bulk analyses including ultraviolet-visible spectroscopy and measurements of electron-donating capacity. Chemical probes are used to quantify steady-state concentrations formed during irradiation and quantum yields for triplet-state DOM (3DOM), singlet oxygen (1O2), and radical species (e.g., hydroxyl radical; ●OH). Surrounding landcover has significant impacts on DOM composition and on resulting PPRI formation. Samples from developed landscapes including agricultural and urbanized watersheds have higher quantum yields for 3DOM and 1O2, while water bodies receiving significant DOM inputs from forests and wetlands generate higher steady-state concentrations of PPRI and have higher quantum yields for ●OH. Quantum yields for 3DOM and 1O2 formation correlate strongly in waters, while ●OH shows opposing relationships to DOM character. Electron-donating capacities provide evidence that these trends are likely due to the mechanism of ●OH formation.

Dissolved organic matter composition and electron-donating capacity determine photochemical reactivity of diverse waters

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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