Xinran Zhang

Abstract Atmospheric nitrous acid (HONO) chemistry is of critical importance to air quality during polluted haze events, especially in China. However, current air quality models (such as WRF-CHEM, WRF-CMAQ, Box-MCM) generally underestimate the concentration of HONO, leading to a lack of fundamental understanding of haze pollution. Here, by combining field observations during haze events in Beijing and modeling results, we developed the new parameterization scheme for heterogeneous nitrogen dioxide (NO 2 ) reaction on aerosol surfaces with the synergistic effects of relative humidity and ammonia, which has not been considered in existing air quality models. Including NO 2 heterogeneous reactions into modeling significantly improves the estimation accuracy of HONO and OH levels, with the contribution reaching up to 91% and 78% during pollution episodes. The OH derived by HONO can partly explain high concentrations of particulate matter. Together, our work provides a new approach to illustrate the formation of HONO, OH, and haze with the consideration of heterogeneous NO 2 → HONO chemistry.

In this study, we first achieve effective generation of reactive chlorine species (RCS) by molecular oxygen (O2) activation on a copper chloride loaded hydrothermal carbonaceous carbon (CuCl-HTCC). O2 can be adsorbed and activated by the cuprous (Cu(I)) from the CuCl-HTCC, and then converted into superoxide radical-hydrogen peroxide-hydroxyl radical, and chloride on the surface of CuCl-HTCC can be converted to RCS. This system holds two advantages: (1) plenty of Cu(I) exists in CuCl-HTCC can contribute to O2 activation heterogeneously. Its efficiency is much higher than that of homogeneous reactions in which Cu(I) cannot exist stably; (2) this process is a rapid heterogeneous process. Cu(I) can contribute to RCS generation with very fast kinetic through multi-steps. As a result, 10 mg/L of pollutants like phenol or ibuprofen were almost completely degraded in 120 min. This is a new and efficient method for generating RCS through the O2 activation process.