Abstract
<title>Abstract</title> <p> This study explored the oxidative potential (OP) of PM <sub>2.5</sub> and its source-specific drivers in an industrial region influenced by petrochemical and steel-related emissions. The chemical and cellular OP were assessed using dithiothreitol (DTT) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, respectively, referred to as quinone-normalized DTT oxidative potential (QDTT-OP) and MTT-based oxidative potential (MTT-OP). The composition of PM <sub>2.5</sub> was primarily dominated by secondary inorganic aerosols and organic carbon, while QDTT-OP exhibited greater temporal variability compared to MTT-OP. Positive matrix factorization (PMF) identified five major sources: vehicle emissions, petrochemical combustion, coke/steel combustion, secondary sulfate, and secondary nitrate. Source profiles revealed that petrochemical combustion was rich in organic markers, whereas coke/steel combustion was characterized by combustion-derived polycyclic aromatic hydrocarbons and related tracers. Multiple regression analysis highlighted distinct source contributions to OP. Petrochemical combustion emerged as the dominant driver of MTT-OP, indicating a strong influence of organic-rich emissions on cellular oxidative responses. Conversely, coke/steel combustion showed the strongest association with QDTT-OP, underscoring the significance of metal-rich industrial emissions in chemical oxidative activity. Normalized regression coefficients further emphasized this contrast. These findings demonstrate that OP is strongly dependent on both source and assay, highlighting the importance of multi-metric approaches and targeted emission control strategies in industrial environments. </p>