Nighttime NO loss and ClNO formation in the residual layer of a polluted region: Insights from field measurements and an iterative box model.

The heterogeneous reaction of dinitrogen pentoxide (NO) on aerosols is an important sink of nitrogen oxides (NO) in the polluted boundary layer, and the production of nitryl chloride (ClNO) can have significant effects on the atmospheric oxidative capacity. However, the heterogeneous loss of NO and the formation of ClNO are still not well quantified, especially in China. In a previous study, we measured ClNO and NO concentrations in several air masses at a high-elevation site in Hong Kong, and found the highest levels ever reported at one night.