Formation and Environmental Risk Assessment of Environmental Persistent Free Radicals and Reactive Oxygen Species on the Surfaces of Phenolic Compounds and Fe(III)-SiO Particulates

Environmental Persistent Free Radicals (EPFRs) are a class of novel pollutants with long lifespans and multi-medium migration characteristics. They can generate highly oxidative Reactive Oxygen Species (ROS), triggering oxidative stress in organisms and subsequently inducing toxicity and health hazards. Therefore, EPFRs and ROS have become key focal points in current environmental risk prevention and control. This study selects catechol (CT) and 4-tert-butylcatechol (TBC) as organic precursors, simulating the generation of EPFRs and ROS on the surface of Fe(Ⅲ)-SiO2 particles, revealing the harmful mechanisms by which both contribute to ecological environmental damage. Concentration gradient experiments show that with the increase in the concentration of phenolic precursors, the amounts of EPFRs and ROS generated also increase. Furthermore, TBC, which contains strong electron-donating groups, has a higher generation capacity than CT, indicating the significant impact of precursor concentration and chemical properties on the generation of EPFRs and ROS. Time decay experiments show that after 456 hours, the EPFRs generated in the CT and TBC systems still maintain high concentrations, indicating the environmental persistence of EPFRs. Toxicity equivalence assessment experiments indicate that the EPFRs generated by the CT and TBC systems correspond to inhaling 3.8-4.0 and 19.4-33.7 cigarettes, respectively, for an adult male at different concentration gradients, with TBC demonstrating stronger health risks. This study clarifies the concentration levels and influencing factors of EPFR and ROS formation on Fe(III)-containing particulate matter surfaces by CT and TBC, investigates the environmental behavior and health risks of CT and TBC, and provides a theoretical basis for assessing the ecological and environmental risks caused by the transformation of phenolic pollutants on particulate matter surfaces.