Development of a quantitative structure-activity relationship model for mechanistic interpretation and quantum yield prediction of singlet oxygen generation from dissolved organic matter.

Singlet oxygen (O) is capable of degrading organic contaminants and inducing cell damage and inactivation of viruses. It is mainly generated through the interaction of dissolved oxygen with excited triplet states of dissolved organic matter (DOM) in natural waters. The present study aims at revealing the underlying mechanism of O generation and providing a potential tool for predicting the quantum yield of O (Φ) generation from DOM by constructing a quantitative structure-activity relationship (QSAR) model. The determined Φ values for the selected DOM-analogs range from (0.54 ± 0.23) × 10 to (62.03 ± 2.97) × 10. A QSAR model was constructed and was proved to have satisfactory goodness-of-fit and robustness. The QSAR model was successfully used to predict the Φ of Suwannee River fulvic acid. Mechanistic interpretation of the descriptors in the model showed that hydrophobicity, molecular complexity and the presence of carbonyl groups in DOM play crucial roles in the generation of O from DOM. The presence of other heteroatoms besides O, such as N and S, also affects the generation of O. The results of this study provide valuable insights into the generation of O from DOM in sunlit natural waters.