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 (ƒTMP) of 3OM∗ were measured for each component and compared to those of reference natural organic matter (NOM). NaBH4 reduction was performed on the EfOM, and the effect of aromatic ketones moieties on triplet formation was also determined. Furthermore, the apparent quantum yield of 1O2 (Φ1O2) and O2•- (ΦO2•-) was measured. Our results suggested that the HPI fraction acted as a sink for 3OM∗. A linear correlation was observed between ƒTMP and Φ1O2 for NOM/EfOM, except for NaBH4-reduced effluent and HPI components. Both ƒTMP and Φ1O2 were positively correlated with the contribution rates of NaBH4-reducible moieties (aromatic ketones) toward 3OM∗. Aromatic ketones were primarily responsible for the production of 3OM∗ from EfOM, whereas quinone moieties played a key role in the production of 3OM∗ 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.