AIRPOLL-Beijing was a collaborative proposal prepared by leading UK and Chinese research groups for a detailed, integrated and wide-ranging study of air pollution sources and related phenomena in Beijing. The overarching aim was to systematically quantity the emission flux of particulate matter, ozone and nitrogen dioxide as well as their precursors (e.g. VOCs, NO, SO2 and NH3) from major sources and to authoritatively assess their contribution to ambient air pollutant concentrations in Beijing. This resulted in a major enhancement to knowledge of the sources of primary and secondary air pollutants in Beijing, and in the capability of models to predict air quality and to develop mitigation measures.

The specific objectives were:
(a) Delivery of comprehensive datasets on air quality and pollutant fluxes from two intensive urban atmospheric pollution measurement campaigns using ground-level and elevated sampling platforms within and close to Beijing.
(b) Provision of in situ characterisation in three spatial dimensions of the chemical and physical properties of urban atmospheric pollutants with a particular focus upon particulate matter, nitrogen dioxide and ozone, taking account of factors influencing population exposure.
(c) Comprehensive source apportionment of atmospheric pollutants at sites within and close to Beijing, using a variety of complementary receptor modelling methods with a thorough estimation of uncertainties.
(d) Making the first direct measurements of fluxes of a comprehensive range of pollutants using the unique 325m IAP meteorological tower in central Beijing, for comparison with existing and refined source emissions inventories.
(e) Estimation of the fluxes of nitrogen dioxide, sulphur dioxide and formaldehyde to the atmosphere from Beijing and the surrounding area, using earth observation data at an enhanced spatial resolution.
(f) Development of enhanced chemistry-transport models with online air pollutant source apportionment capability and a hybrid receptor and chemistry-transport pollutant source apportionment model for the greater Beijing urban area.
(g) Provision of a three dimensional source, sector and region-oriented source apportionment of atmospheric pollutants, including primary particles and their chemical constituents, secondary particulate matter and gaseous pollutants in Beijing and the North China Plain through CTM.
(h) Assessment of the performance of receptor models and chemical transport models in source apportionment of pollutants in Beijing and to harmonise the two independent approaches.
(i) Integration of results from the flux measurements, satellite retrievals, receptor models and chemistry-transport models to iteratively enhance the emissions inventory for Beijing and its surroundings, and hence optimise the performance of predictive models.
(j) Integration of these activities with other themes in the research programme concerned with atmospheric processes affecting air pollution, exposure science and impacts upon health, and interventions and solutions.

Beijing suffers from very high concentrations of airborne pollutants, leading to adverse health and wellbeing for over twenty million people. The pollutants likely to have the greatest effects upon human health are particulate matter, nitrogen dioxide and ozone. Both particulate matter and nitrogen dioxide are emitted directly from individual sources (primary contributions, many of which are not well quantified); and are formed in the atmosphere (secondary contributions, which are highly complex). Ozone is entirely secondary in nature, formed from reactions of precursor gases, whose sources and abundance are also challenging to constrain. These uncertainties hinder understanding of the causes of air pollution in Beijing, which is needed to deliver effective and efficient strategies for pollution reduction and health improvement.

AIRPOLL-Beijing project addressed this challenge, through identification and quantification of the sources and emissions of air pollutants in Beijing. The project sat within the NERC/MRC-NSFC China megacity programme, which includes projects addressing the atmospheric processes affecting air pollutants, human exposure and health effects, and solutions / mitigation strategies to reduce air pollution and health impacts. The project exploited the combined experience and expertise of leading UK and Chinese scientists, applying multiple complementary approaches. The project deployed multiple atmospheric measurement and analysis strategies to characterise pollutant abundance and sources, develop novel emissions inventories, and integrate these to produce new modelling tools for use in policy development. The project adopted a range of state-of-the-science approaches: -Receptor Modelling, where detailed composition measurements are used to infer pollutant sources from their chemical signatures, combining world-leading UK and Chinese capability. -Flux Measurements, where the total release of pollutants from all sources is measured, providing a key metric to refine emission inventories. The project combined near-ground measurements (using the unique Institute of Atmospheric Physics 325m tower in central Beijing), ground-based observations and fluxes derived from satellite observations. -3D spatial analysis, in which a novel sensor network will be deployed around central Beijing to measure pollutant fields. -Development of novel emissions inventories, which predicted the temporally- and spatially- resolved emissions of air pollutants from all sources, enhancing existing capability. -Development of new online modelling tools, within which to integrate emissions, atmospheric processing and meteorology to predict primary and secondary pollutant concentration fields.

AIRPOLL-Beijing integrated these approaches to provide thorough understanding of the sources and emissions of air pollutants in Beijing, at unprecedented detail and accuracy. While the project was a self-contained activity, key deliverables feed into Processes, Health and Solutions themes of the programme. This proposal seeks Newton fund support, part of the UK's Official Development Assistance (ODA) commitment. The project directly addressed ODA objectives, in the categories of (i) people (through the joint development of novel scientific approaches to the understanding of megacity air pollution), (ii) programmes (as all aspects of the project are joint UK-Chinese research endeavours) and (iii) translation (through provision of detailed air pollution source assessments, in support of assessment of health impacts and development of mitigation strategies). More generally, the project left a legacy of improved air pollution understanding and research capacity of the Chinese teams, and, through integration with other themes of the Megacities programme, underpin improvements in the health and welfare of the population of Beijing, and across China more widely - ultimately benefitting more th