NO3·-Initiated Gas-Phase Formation of Nitrated Phenolic Compounds in Polluted Atmosphere.

Abstract

Organic nitrogen (ON) compounds are key contents of particulate matter in the megacities of Asia. As a series of important ON, nitrated phenolic compounds (NPs) are of high concentration in the atmosphere, although their formation mechanism and role in particulate nucleation and growth are not fully understood. Herein, using a high level of quantum mechanical calculations, we explore the formation paths of NPs initiated by NO3· radicals, where some common atmospheric species, such as H2O, (H2O)2, NH3, and dimethylamine (DMA), can act as molecular catalysts. The kinetic study predicts that the formation rate of methyl nitrophenols with the assistance of DMA and (H2O)2 can reach ∼103 molecules·cm-3·s-1 in a polluted and humid atmosphere. The volatilities obtained from the empirical model show the formed NPs mainly belong to the intermediate and semivolatile organic compounds, which can participate in the growth process of aerosols rather than the early stage of cluster nucleation. Moreover, some NPs can be salified with atmospheric bases to further increase their contributions to the particulate formation.