Occurrence and Concentration of Micropollutants in the Middle-and Down-stream of Nakdong River

The Nakdong River runs through highly industrialized and populated areas and has thus been polluted with numerous anthropogenic chemicals. As a growing number of new chemicals have been developed and used, the complexity of pollution in the receiving water has increased. In this study, LC-HRMS-based quantitative analysis was performed on 174 micropollutants in order to understand the status of new trace pollutants occurring in the middle and lower sections of the Nakdong River. In this analysis, 106 substances were detected at concentrations above the LOQ. Benzotriazole, used as a rust inhibitor, showed the highest median concentration, followed by metformin and diethylene glycol dibenzoate, all with maximum concentrations above 1,000 ng/L. Among pharmaceuticals, metformin, valsartanic acid, metoprolol acid, and carbamazepine had high median concentrations. Similarly, high concentrations were observed for metolachlor ESA, 2-aminobenzimidazole, and flubendiamide among pesticides, and benzotriazole, diethylene glycol dibenzoate, and dimethyl phthalate among industrial agents and other substances. The sample collection point with the highest number of substances detected was point N3, which also showed the greatest sum of median concentrations. With respect to substance groups, the highest median concentration levels were found at N2 for pharmaceuticals, N1 for pesticides, and N3 for industrial chemicals. Among the detected trace pollutants, a total of 44 substances were selected as priority substances after considering domestic and international water quality standards, detection concentration and frequency, and toxicity. These substances are suggested for preferential monitoring and management in the middle and lower sections of the Nakdong River.