A Survey of N-nitrosamines in Namhan River and Natural Solar Photolysis of N-nitrosamines

This study aimed to evaluate the impact of sunlight on the behavior of N-nitrosamines in the Jugdangcheon stream, a tributary of the Namhan River. N-nitrosamines were monitored over four occasions in 2024, and experiments were conducted to investigate their decomposition under natural sunlight, considering variables such as radiation intensity and initial concentration. More than 50% of the concentrations of the eight types of N-nitrosamines detected at all sampling points were NDMA and NDEA. The analysis of samples collected in June revealed that the total concentration of N-nitrosamines decreased by 76% from the S1 to the S3 point. The results of the N-nitrosamines decomposition experiment under natural sunlight showed that, in November, when solar radiation intensity was the lowest, the reaction rate constants for the eight types of N-nitrosamines ranged from 0.018 to 0.025 min⁻¹ (average 0.020 min⁻¹). In contrast, in June, when solar radiation intensity was the highest, the reaction rate constants ranged from 0.042 to 0.053 min⁻¹ (average 0.048 min⁻¹). These findings are consistent with the results of previous UV-based experiments, and thus, it can be concluded that sunlight may be one of the factors influencing the variation in N-nitrosamine concentrations in the Jugdangcheon stream.