Associations between Environmental Persistent Free Radicals, Reactive Oxygen Species, and Oxidative Potential in Atmospheric Aerosols

Environmentally persistent free radicals (EPFRs) and reactive oxygen species (ROS) play critical roles in the oxidative toxicity of atmospheric particulate matter (PM). This study analyzed size-resolved PM from four functional zones─ocean, traffic, construction, and canteen─in Xiamen to investigate the characteristics of EPFRs, ROS, and oxidative potential (OP). Research results show that the canteen zone exhibited the highest EPFR concentrations (9.12 × 1013 spins/m3), which is related to cooking fume emissions and gas combustion. EPR results showed oxygen-centered radicals (g > 2.0040) dominating traffic and ocean PM, whereas construction and canteen samples contained mixed radical types with broader line widths. Aqueous extracts of PM generated substantial amounts of hydroxyl radicals (·OH) and organic radicals (·R). OPmDTT for samples in the four areas is 24.22(±4.90) nmol/min/μg (canteen), 5.90(±2.13) nmol/min/μg (traffic), 6.24(±2.60) nmol/min/μg (construction), 22.21(±13.69) nmol/min/μg (ocean). Canteen and ocean aerosols exhibited relatively high OP despite lower transition-metal content, indicating the involvement of EPFRs and organic components beyond classical metal-driven pathways.