An integrated study of air pollution processes in Beijing (AIRPRO)

UK principal investigator: Professor Alistair Lewis, University of York, and the National Centre for Atmospheric Science

Chinese principal investigator: Professor Pingqing Fu, Institute of Atmospheric Physics (CAS)

WP1: Oxidation chemistry

Identify the dominant oxidative degradation pathways in Beijing via hydroxyl (OH) and nitrate (NO 3) radicals and O3 reactions, and test these against explicit chemical mechanisms (the Master Chemical Mechanism (MCM)). Assessment of detailed gas and aerosol composition, and integrated chemical properties such as OH lifetime and ozone production efficiency, will help quantify rates of photochemical smog formation, disaggregate transport from processing of local emissions, and provide a reference for all model simulations with a range of scheme complexities.

WP2: Nitrogen budgets

Establish the total reactive nitrogen source and sink budget for Beijing, the role of nitrogen reservoir species in determining local and regional ozone concentrations and in controlling gas­to­particle transfer to aerosols. This will include an evaluation of the combined impact of anthropogenic (including agricultural) and biogenic (vegetation) emissions on the nitrogen budget via organic nitrate formation.

WP3: Aerosol Physical and Optical Properties

Develop a detailed description of physical and optical properties, pollution loadings and the influence of humidity tailored to the high haze environment of Beijing, and assess the impacts of aerosols on photochemical processes. The developments would be informed and evaluated via comparison with observations of optical and physical properties, including water uptake, using measurements made under a range of atmospheric conditions.

WP4: Secondary aerosols

Establish experimentally the contributions of secondary aerosols to haze abundance in Beijing and the rates of production from precursors such as SO2, NH4 and organic compounds. This objective will combine detailed gas phase observations of condensable gases from WP1 and 2 (both organic and inorganic) with measurement of their partitioning into PM, and abundance in PM via a range of experiment measurement techniques, both on and off­line.

WP5: Urban meteorology

Quantify the influence of tall buildings in Beijing on dispersion, flow, thermal mixing and urban surface­atmosphere exchanges, for the urban canopy layer (micro scale), above the roughness sub­layer (neighborhood scale) and the urban boundary layer (city scale). This will be achieved through a combination of field measurements, wind tunnel experiments and numerical modelling.

WP6: Feedbacks between haze, photochemistry and dynamics

Develop strategies to use the observational data from WP3 to study the links and feedbacks between the pollution particulate loading and the photochemical and dynamical processes that lead to the most severe build­up of pollution in inversion events, integrating fundamental understanding with local factors unique to Beijing.

WP7: Integration via multi­scale modelling

Exploit regional and urban­scale models to enhance process understanding using results from the WPs above. This will enable a seamless scale up of new understanding from detailed process models, via reduced chemistry schemes, to regional models, and permit simulation of regional to urban chemistry­aerosol­meteorology­ haze interactions. The insights gained from comparison with observations will be used to guide model enhancements for improved model simulations at street level, a necessity for exposure studies.