Evidence of heterogeneous Hono formation from aerosols and the regional photochemical impact of this Hono source

Large missing daytime HONO sources have been reported by many previous studies around the world. Possible HONO sources include ground heterogeneous conversion, aerosol heterogeneous formation, soil emission, and photochemical production. In this study, a consistent 1-D framework based on regional and 3-D chemical transport models (CTMs) was used to analyze the unknown daytime HONO sources in 14 cases worldwide. We assume that the source of HONO from aerosols is through NO2 hydrolysis (not including its oxidation products) and that non-local mixing effect is negligible. Assuming all the missing unknown HONO source is from the ground, it would imply a NO2-to-HONO ground heterogeneous conversion exceeding 100% in daytime, which is unphysical. In contrast, a strong R2 reaching up to 0.92 is found between the unknown HONO sources and the products of aerosol wet surface area and short-wave radiation (SWR). Because the largest unknown daytime HONO sources are found in China due to high concentrations of aerosols and NO2, we derive an optimized aerosol daytime HONO source formulation on the basis of these measurements. The 3-D CTM simulations suggest that in some regions of central, eastern, and southwestern (e.g., SiChuan province) China, the aerosol HONO source has the greatest effects on ozone (>10 ppbv) and OH (>200%) in winter. In January, the simulated particulate sulfate level over these three regions increases by 6 to 10 μg/m3 after including the aerosol-HONO source, which helps reduce the previous model underestimation of sulfate production in winter. Additional measurement studies that target the daytime HONO sources will be essential to a better understanding of the mechanisms and resulting effects on atmospheric oxidants

Aerosol · Air quality index · Atmospheric chemistry · Atmospheric sciences · Chemical transport model · Daytime · Geography · Meteorology · Mixing ratio · Ozone · Photochemistry · Sulfate · Air Quality and Health Impacts · Atmospheric chemistry and aerosols · Atmospheric Ozone and Climate · Chemistry · Environmental Science · Environmental Chemistry · Geology

• Impact of aerosol–meteorology interactions on fine particle pollution during China’s severe haze episode in January 2013

  Open Access•Jiandong Wang, Shuxiao Wang et al.•Environmental Research Letters•2014

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