Photodegradation of acebutolol in natural waters: Important roles of carbonate radical and hydroxyl radical

Acebutolol (ACE) has been widely used for the treatment of cardiovascular disorders, and its photochemical fate in natural waters is a matter of concern due to its ubiquitous occurrence and its toxicity to aquatic organisms. In this study, the photodegradation of ACE in river water and synthetic waters were investigated under simulated sunlight irradiation. The results demonstrated that ACE photodegradation rate in river water was 3.2 times higher than that in pure water. Then the influences of HCO3- , NO3- and DOM on ACE photolysis were investigated under their concentrations similar with the ones in river water. ACE photodegradation was significantly enhanced in the presence of HCO3- alone, and the scavenging experiments and the electron paramagnetic resonance experiments together proved that HCO3- could be oxidized by triplet-excited state of ACE to generate CO3 center dot-, which subsequently played a key role in ACE degradation. The presence of both NO3- and DOM also increased the ACE photodegradation rates, and center dot OH and 3DOM* were found to be involved in the degradation. In addition, when DOM was added to a solution with HCO3, the enhancement effect of HCO3- on ACE photodegradation was weakened due to the scavenging of CO3 center dot- by DOM combined with the light screening effect of DOM.