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Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures
Published on: January 7, 2019
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Dissolved Organic Matter Photoreactivity Is Determined by Its Optical Properties, Redox Activity, and Molecular
Stephanie M Berg1, Kristine H Wammer2, Christina K Remucal1,3
1Environmental Chemistry and Technology Program, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States.
Environmental Science & Technology
|April 11, 2023
Summary
Predicting photochemical reactive intermediates from dissolved organic matter (DOM) is complex. This study links DOM composition to the formation of triplet-state organic matter, singlet oxygen, and hydroxyl radicals, revealing distinct molecular origins for each.
Area of Science:
- Environmental Chemistry
- Photochemistry
- Organic Geochemistry
Background:
- Predicting the formation of photochemically produced reactive intermediates (PPRI) from dissolved organic matter (DOM) is challenging due to DOM complexity and varied formation mechanisms.
- Understanding PPRI formation is crucial for predicting DOM photoreactivity in aquatic and wastewater systems.
Purpose of the Study:
- To investigate the role of DOM composition in photoreactivity.
- To relate quantum yields of key P P R I (excited triplet-state organic matter, singlet oxygen, hydroxylating species) to DOM characteristics.
- To determine if bulk properties or molecular-level composition better predicts PPRI formation.
Main Methods:
- Analysis of 48 freshwater and wastewater DOM samples.
- Spectroscopic techniques (UV-vis) and Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) for DOM characterization.
- Measurement of quantum yields for triplet-state organic matter (fTMP), singlet oxygen (Φ1O2), and hydroxylating species (Φ•OH).
- Correlation analysis and multiple linear regressions linking DOM properties to quantum yields.
Main Results:
- fTMP and Φ1O2 trends correlated with bulk DOM properties (UV-vis spectra, electron-donating capacity (EDC)).
- No single bulk property could predict Φ•OH formation.
- Molecular-level analysis revealed distinct DOM fractions responsible for Φ•OH and 1O2 formation.
- Complementary analytical techniques are necessary for comprehensive DOM characterization.
Conclusions:
- DOM composition significantly influences the photoreactivity and PPRI formation.
- Excited triplet-state organic matter and singlet oxygen originate from similar DOM fractions, predictable by bulk properties.
- Hydroxyl radical formation is linked to a distinct molecular subset of DOM.
- Integrated analytical approaches are essential for accurately predicting PPRI formation from complex DOM.
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