Photochemical fate of emerging pollutants in the urbanized river: effects of antropogenic and natural water components

Emerging contaminants (ECs) in freshwater ecosystems are increasing with urbanization. Although some of ECs are listed as specific pollutants according to the European Water Framework Directive, there is relatively little information on the photochemical fate of various ECs. In this study, simultaneous degradation of six model ECs was investigated in both synthetic solution and Ergene River water samples by exposing them to the simulated solar light. This study was not only focused on the photodegradation of spiked ECs to the river water, but also the contaminants already found in river water. The laboratory experiments were conducted in a way to explore the direct and indirect photolysis pathway. To clarify the effects of water components on the photodegradation kinetics of model ECs in eight river water samples, which were obtained from the region far away from industrial activities, but close to the agricultural and residential activities, were characterized with organic and inorganic parameters. The detected ECs, which were four industrial pollutants and two pesticides in the river water samples regardless of the sampling site, were persistent to photodegradation while the complete degradation of ciprofloxacin, clothianidin, imazamox, imidacloprid, tetracycline and triclosan spiked at 100 mg L-1 concentration was achieved within 300 min irradiation time with 1360 W m-2 light intensity even in the water matrix receiving the effluent of a wastewater treatment plant. Direct photolysis was a significant pathway for ciprofloxacin, tetracycline and triclosan. The different optical properties both river water samples and ECs have the contribution on their photodegradation rate constants.