The determination and prediction of the apparent reaction rates between excited triplet-state DOM and selected PPCPs

To determine and predict the reaction rate between 3 DOM* and PPCPs in various water bodies, this study defines a reaction rate coefficient ( α 3 DOM ∗ ) to describe the reaction between 3 DOM* and PPCPs. As the values also included the inhibition effect of DOM's antioxidant moieties, the calculation of α 3 DOM ∗ is inconsistent with that of a bimolecular rate constant via the steady-state kinetic method. The α 3 DOM ∗ values of 12 selected PPCPs were determined in two DOM solutions and ten DOM-containing water samples collected from typical surface water bodies in Beijing. The Pearson coefficients between nine predictors including the absorbance ratio (E2/E3), specific absorption coefficient at 254 nm (SUVA 254 ), fluorescence index (FI), biological index (BIX), humification index (HIX), pH, total organic carbon (TOC), total fluorescence intensity (TFI) and TOC normalized TFI (TFI/TOC) and α 3 DOM ∗ were examined. Correlation patterns for sulfonamides, β-blockers and diclofenac supported the electron transfer pathway, and was distinctly different from those appeared for FQs where quenching effect played a main part. TFI and TFI/TOC were recognized as the most useful surrogates in empirically predicting α 3 DOM ∗ . For PPCPs that went through the electron transfer pathway, α 3 DOM ∗ could be well fit to the Rehm-Weller model assuming a proportional relationship between TFI and △G et . For FQs, α 3 DOM ∗ was found to linearly correlated with TFI/TOC. The α 3 DOM ∗ values determined in this study enrich the database of PPCPs photolysis parameters, and the correlation analysis provides reference for forecasting PPCPs fate in the aquatic environment.