McFAN experiment: An integrated analysis of the multiphase chemistry experiment in Fogs and Aerosols in the North China Plain

Fine-particle pollution associated with winter haze threatens the health of more than 400 million people in the North China Plain. The Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain (McFAN) investigated the physical-chemical mechanisms leading to the haze formation with a focus on the contributions of multiphase processes in aerosol and fogs. We integrated multiple platform observations with regional and box models to identify the key oxidation process producing sulfate, nitrate and secondary organic aerosols, and their impact. A new environmental chamber was deployed to conduct kinetic experiments with real atmospheric compositions in comparison to literature kinetic data from laboratory studies. The experiments were carried out for multiple years since 2017 at the Gucheng site in the center of polluted areas and have performed experiments in the winter season. The location of the site minimizes fast transition between clean and polluted air masses (e.g., in Beijing), and helps to maintain a pollution regime representative for the North China Plain. The multi-year consecutive experiments documented the trend of PM2.5 pollution and corresponding change of aerosol physical and chemical properties, and allowed to investigate newly proposed mechanisms. The preliminary results show new proofs of the key role of aqueous phase reactions in regulating the aerosol compositions during haze events.

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