Environmental photochemical fate of selected pharmaceutical compounds in natural and reconstituted Suwannee River water: Role of reactive species in indirect photolysis

Abstract

This study reports the impact of two reactive species, hydroxyl radical and singlet oxygen, on the photochemical degradation of three selected pharmaceutical compounds in natural and reconstituted solutions of Suwannee River water. Absolute bimolecular rate constants (M-1s-1) were determined for the reaction of hydroxyl radical and singlet oxygen with danofloxacin ((6.15±0.11)×109; (7.50±0.13)×104), fluvastatin ((6.96±0.16)×109; (1.64±0.18)×108), and paroxetine ((8.65±0.12)×109, (1.18±0.13)×108), respectively. For all three pharmaceutical compounds, the rate constants for reactions with the hydroxyl radical were similar; however, those for singlet oxygen varied by three orders of magnitude. In the waters studied, the steady-state concentration of the hydroxyl radical was on the order of 10-17-10-18M, and for singlet oxygen, 10-12-10-14M. The percent contribution of each species to the degradation of each pharmaceutical in each water matrix was calculated, and several trends were identified enabling a better understanding of the role of these reactive species.