Chemical and optical phototransformation of dissolved organic matter

Dissolved organic matter represents the main reservoir of organic carbon in most aquatic ecosystems. In the present study, we determined the optical changes and the quantum yields of transient species formation for chromophoric dissolved organic matter (CDOM) samples undergoing photodegradation. The results show that the triplet states 3CDOM∗ are potentially key players in CDOM photodegradation and that such transformations are strongly influenced by small differences in CDOM sources and sinks. In contrast, OH radicals are very unlikely to play a key role in phototransformation. These results represent an important first step in combining optical and transient species analyses to understand photodegradation processes of dissolved organic matter.

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► Indirect phototransformation of dissolved organic matter causes both chemical and optical changes.
► Photo-induced changes in absorption and absorption slopes have spectral distributions.
► Triplet states 3CDOM* play a key role in CDOM photodegradation.
►  Small differences in sources and sinks influence photodegradation rates.