Major influence of hydroxyl and nitrate radicals on air pollution by environmentally persistent free radicals

摘要

Environmentally persistent free radicals are pollutants recently detected in most environmental matrices such as fly ash, aerosols, soils and sediments. Their generation and transformation is poorly known, notably in the atmopshere. Here we modeled the effect of dioxygen O-2, hydroxyl radical (OH)-O-center dot, and nitrate radical NO3 on Cu(II)O surface-bound phenoxyl radical, using quantum chemical calculations and kinetics analysis. Results show that additional stabilization of the surface-bound phenoxyl radical is provided by the metal-oxide surface, implying that self-decomposition is not likely to occur. The addition reactions of hydroxyl and nitrate radicals with surface-mediated radicals are both thermodynamically and kinetically favorable, whereas the role of O-2 appears negligible. The tropospheric lifetime of the Cu(II)O-based surface-bound phenoxyl radical is only few seconds to about one hour, in agreement with experimental observations from the literature.