Distribution of Heavy Metals and Organic Compounds: Contamination and Associated Risk Assessment in the Han River Watershed, South Korea

Given water pollution increases in aquatic ecosystems resulting from industrialization and rapid urbanization, appropriate treatment strategies to alleviate water pollution are crucial. The spatiotemporal distribution, sources, and potential risk of heavy metals and organic compounds were determined in surface water from the Han River watershed (n = 100) in wet and dry seasons. The inductively coupled plasma mass spectrometer (Cr and As), mercury analyzer (Hg), and ultra-high performance liquid chromatography tandem mass spectrometer (organic compounds) were used to analyze the target compounds. Total concentration and detection frequency were in the order: Cr (2.375 µg/L, 100%) > As (1.339 µg/L, 100%) > Hg (0.007 µg/L, 100%) for heavy metals, and carbofuran (0.051 µg/L, 75%) > bisphenol A (0.040 µg/L, 47%) > quinoline (0.020 µg/L, 32%) for organic compounds. The target compounds showed the highest concentration in the area near industrial facilities. High concentrations and risk levels of all target compounds, except quinoline, were observed during the wet season. Principal component analysis indicated anthropogenic activities were the primary source of pollution. Cr showed the most prominent environmental impact in the wet season, suggesting its ecological risk. Additional monitoring is required for clear risk pollutant assessments in aquatic ecosystems to aid policy implementation.