Atmospheric heterogeneous reaction of chlorobenzene on mineral -Fe₂O₃ particulates: a chamber experiment study

Despite the large emission of chlorinated volatile organic compounds (CVOCs) into the atmosphere, the ultimate fate of these compounds remains largely unknown. Herein, we explore the photochemical conversion of an important class of CVOCs, namely chlorobenzene (CB), on mineral a-Fe2O3 particulates under atmospheric relevant conditions. A series of chamber reactions composed of the CB with/without SO2 or NO2 are performed, followed by in situ diffuse reflectance infrared Fourier transform spectroscopy measurements and density functional theory calculations. We show that CB can be considerably degraded by a-Fe2O3 under light irradiation, whereas the reaction is markedly suppressed by adding SO2 or NO2 owing to their competitive adsorption and surface acidification. In particular, we discover that CB can be ultimately converted into polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) under dark state or light irradiation, suggesting a possible origin of atmospheric PCDD/Fs from this overlooked photochemical source.