Association between time of day and carbonaceous PM2.5 and oxidative potential in summer and winter in the Suncheon industrial area, Republic of Korea

PM 2.5 samples were collected in Suncheon during the summer (June 2–11, 2023) and winter (January 15–21, 2024). The chemical composition analysis included carbonaceous components (OC, EC), secondary ionic components (NH 4 + , NO 3 − , SO 4 2− ), dithiothreitol - oxidative potential (QDTT-OP), and volatile organic compounds. Results showed higher summer PM 2.5 concentrations due to photochemical reactions and higher winter concentrations from heating and stable atmospheric conditions. The OC/EC ratio indicated greater secondary organic aerosol formation in summer. Oxidative potential (QDTT-OP v ) was higher in summer (0.12 µM/m³) than winter (0.09 µM/m³), correlating strongly with OC in summer. Health risk assessment of BTEX revealed higher concentrations in winter, with benzene as the primary contributor to lifetime cancer risk (LTCR). The cumulative hazard quotient (HQ) was higher in winter, indicating increased non-carcinogenic risk. The study highlighted that oxidative potential is more influenced by chemical composition than physical characteristics, suggesting that regulating PM 2.5 concentration alone may be insufficient. VOCs, as precursors of SOA, showed a positive correlation with QDTT-OP v , with benzene exhibiting the strongest correlation in winter. These findings emphasize the need for targeted management of specific PM 2.5 components to mitigate health risks effectively. Graphical Abstract