Abstract:The indirect photodegradation behavior and mechanism of SCP were studied by using CDOM that as the main photosensitizer. The effects of CDOM composition, salinity and pH on indirect photodegradation of SCP were analyzed. When CDOM concentration increased, the indirect photodegradation rate of SCP accelerated obviously. Upon irradiation, CDOM produced a variety of active substances, and the different active substances had different contribution rates to the indirect photodegradation of SCP, especially the 3CDOM* played a major role in the indirect photodegradation of SCP and its contribution rate was up to 77.94%. The CDOM used in the experiment was composed of four components, including three terrestrial humus (C1, C2, C3) and the marine humus (C4). The order of the correlation between the SCP removal rates and the four fluorescence components was C3>C2>C4>C1. The correlation between four fluorescence components and [3CDOM*] were also ranked as the former. C3 and C2 components had a significant correlation with [3CDOM*] (R2>0.97), that demonstrated the C3 and C2 components made great contributions to the production of [3CDOM*]. Salinity and pH value had significant effects on indirect photodegradation of SCP. When the salinity of the solution was equal to 15‰, the SCP indirect photodegradation rate reached a maximum. In the low salinity range (0~15‰), the promotion effect of ionic strength was greater than the inhibition effect of inorganic anions that made the indirect photodegradation rate greater with the increase of salinity. When the pH of the solution was equal to (5.00±0.10), the SCP indirect photodegradation rate reached a maximum. The indirect photodegradation rate of SCP slowed down with the increase of pH value of the solution, and the neutral and alkaline environments had negative effects on the indirect photodegradation of SCP.
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