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Updated: Jun 3, 2025

Production and Measurement of Organic Particulate Matter in the Harvard Environmental Chamber
Published on: November 18, 2018
Integrating the updated HONO formation mechanism to better understand urban O3 formation chemistry
Ze Qin1, Yanhui Liu2, Wenyu Bai2
1State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China; School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK.
Abstract:
As a vital precursor of hydroxyl radicals (OH), atmospheric nitrous acid (HONO) plays a significant role in tropospheric chemistry and the production of secondary pollutants. However, knowledge of its sources remains insufficient. To comprehensively investigate the HONO chemistry in polluted cities and alleviate O3 pollution, based on a comprehensive HONO-related field campaign in Zibo City, on the North China Plain, the parameterized formulas of additional HONO sources were validated in a box model (based on the default MCMv3.3.1) and the resulting chemical impact of HONO was determined. The results showed that the updated mechanism well reproduced the diurnal profile of observed HONO, and budget analysis revealed the predominant role of the NO2 photo-enhanced heterogeneous reaction on the ground surface in HONO formation, with contributions of about 70% during both high-O3 episodes and clean days. Underestimations of 32.1% in net Ox production rate and 28.5% in HOx concentrations were simulated by the default mechanism when HONO was not constrained, while the adoption of the updated mechanism reduced these underestimations to 5.3% and 5.4%, respectively. Additionally, sensitivity tests of NOx emission changes showed that the urban O3 photochemical regime was more inclined to NOx-limited after considering variations in HONO concentrations caused by changes in NOx concentrations. These results can contribute to more precise O3 pollution control strategies in urban areas, especially in regions lacking HONO observations.
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