Insights into the photo-induced formation of reactive intermediates from effluent organic matter: The role of chemical constituents

In the present study, the formation of triplet states of organic matters (³OM^∗) from effluent organic matter (EfOM) under simulated solar irradiation was investigated. EfOM was separated into hydrophobic (HPO), transphilic (TPI), and hydrophilic (HPI) components. The quantum yield coefficients (ƒ_TMP) of³OM^∗were measured for each component and compared to those of reference natural organic matter (NOM). NaBH₄reduction was performed on the EfOM, and the effect of aromatic ketones moieties on triplet formation was also determined. Furthermore, the apparent quantum yield of¹O₂(Φ_1O2) and O₂^•−(Φ_O2•−) was measured. Our results suggested that the HPI fraction acted as a sink for³OM^∗. A linear correlation was observed between ƒ_TMPand Φ_1O2for NOM/EfOM, except for NaBH₄-reduced effluent and HPI components. Both ƒ_TMPand Φ_1O2were positively correlated with the contribution rates of NaBH₄-reducible moieties (aromatic ketones) toward³OM^∗. Aromatic ketones were primarily responsible for the production of³OM^∗from EfOM, whereas quinone moieties played a key role in the production of³OM^∗in NOM-enriched solutions. Understanding the role of chemical constituents on the photo activity of EfOM/NOM is essential for providing useful insights on their photochemical effects in aquatic systems.