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NO 2 is a significant primary atmospheric pollutant that plays a key role in atmospheric chemistry. It serves as a crucial precursor to photochemical smog, acid rain, and secondary particulate matter and is instrumental in determining the atmospheric oxidation capacity. In this review, we focus on the heterogeneous chemistry of NO 2, which has been demonstrated to significantly influence the sources and sinks of various nitrogen-containing species through field measurements and model simulations. We provide a comprehensive summary of laboratory studies investigating the reaction mechanisms and uptake kinetics of NO 2 in heterogeneous reactions. NO 2 can undergo disproportionation reactions on atmospheric particles. For instance, it may hydrolyze on wetted surfaces to form HONO and HNO 3, produce nitrate and NO on mineral dust, or generate nitrate and NOCl on sea salt. Additionally, NO 2 can be reduced to HONO on soot and Fe-bearing minerals or photocatalytically reduced to HONO and NO on photosensitive components. Furthermore, NO 2 can be photo-oxidized to nitrate or N 2 O 5 on illuminated TiO 2 . In addition, the synergistic effect of the heterogeneous reactions between NO 2 and SO 2 is discussed. The uptake coefficients of NO 2 on typical particles and the factors influencing these coefficients are also summarized. Finally, based on the current insufficient understanding of heterogeneous reactions of NO 2, we propose prospects for future research.
Xuan et al. (Fri,) studied this question.