Airborne particles have a major impact on our planet’s atmosphere and the megacities of China – vast swathes of humanity living, working and breathing together in cities of up to 26 million inhabitants. Although air quality in Chinese cities has been steadily improving, the levels remain above WHO guidelines. Thus air pollution and its ensuing health issues are of paramount importance to the leaders of China’s biggest cities.
Delivering a comprehensive study five years in the making, more than 150 scientists from China and the UK have joined forces to understand the causes and impacts of air pollution in Beijing. Using novel observational and modelling tools, the Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) research programme has provided new insights on air quality and health as well as practical approaches to reduce pollution exposure and improve health, through a win-win British-Chinese partnership.
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Jointly funded by the Natural Environment Research Council (NERC), Medical Research Council (MRC), Newton Innovation Fund, and the National Natural Science Foundation of China (NSFC), the APHH-Beijing team has addressed key policy-relevant air pollution challenges, such as the role of road traffic and long-range transport in influencing air quality. The team has contributed to over 400 international peer-reviewed scientific journal papers and in their final report, among other things, reveal that:
- Sources of key air pollutants in Beijing’s city centre, including fine particles, nitrogen oxides (NOx), volatile organic compounds (VOC), and black carbon are much lower than predicted, but concentrations were very high, indicating they were created outside the city centre. Road traffic is not a major source of PM2.5, but remains a significant source of NOx.
- Beijing’s air quality has improved dramatically in the last few years, owing to the emission reductions following the implementation of clean air actions.
- Biomass and coal burning outside Beijing produce fine airborne particles (PM2.5) that are carried into the city by air masses along four main routes out of North Shanxi Province, Heze and the neighbouring cities of Tianjin and Tangshan. Cutting ammonia emissions could significantly reduce concentrations of PM2.5.
- Ozone pollution is high in summer and will worsen with future NOx and PM2.5 controls, unless key Volatile Organic Compound (VOC) emissions are regulated. VOCs from fuel evaporation, as well as domestic and industrial solvent consumption contribute most to local ozone formation.
- China’s clean energy transition for rural domestic use slashed ambient PM2.5 levels, but domestic solid fuel burning still created about 20% of ambient PM2.5 in 2012. Cooking oil emissions are a potential source of potentially hazardous fine particles in Beijing - suggesting a more stringent control of this local source may be needed.
- Citizens’ mental health begins to suffer when air pollution levels rise significantly. Negative emotions occurred when the Air Quality Index (AQI) of PM2.5 increases to about 150.
Professor Roy Harrison, from the University of Birmingham is lead UK principal investigator of the largest project within APHH-Beijing - ‘Sources and Emissions of Air Pollutants in Beijing (AIRPOLL-Beijing)’ - the most comprehensive air pollution measurement campaign ever mounted in China, which underpins improvements in health and welfare of Beijing citizens and people across China - ultimately benefitting more than a billion people.
“High levels of air pollution pose a serious health risk to inhabitants of many Chinese cities. We confirmed that Beijing’s air quality has improved significantly in recent years, but air pollution levels are still well above the WHO guidelines, leading to poor health and wellbeing for over 20 million people.
“Our measurement work in Beijing has given us a much greater understanding of air pollutants in Beijing – where the pollution is coming from and how much there is. This, in turn, allows us to make recommendations to policy makers and help them make the decisions that will reduce air pollution levels in Beijing and other cities across China.”
The scientists used the Institute of Atmospheric Physics’ (IAP) 325-meter meteorological tower to measure how pollution composition and levels change at different heights above the city – using multiple atmospheric measurement and analysis strategies to determine where the pollution is coming from and how much there is.
The APHH team developed a range of state-of-the-art scientific approaches to record emissions - integrating these to produce new modelling tools for use in policy development.
Receptor modelling allowed the scientists to record detailed composition measurements and infer pollutant sources from their chemical signatures - combining world-leading British and Chinese capability. Flux measurements recorded the total release of pollutants from all sources, providing a key metric to refine emission inventories that combines near-ground measurements, ground-based observations and fluxes derived from satellite observations.
A novel sensor network deployed around central Beijing measured pollutant fields to create a 3D spatial analysis of air pollution, whilst novel emissions inventories allowed prediction air pollutant emissions from all sources, enhancing existing capability. New online modelling tools enabled integration of emissions, atmospheric processing and meteorology to predict primary and secondary pollutant concentration fields.
Professor Zongbo Shi, from the University of Birmingham, is the science co-ordinator of APHH-Beijing.
“Our research programme generated a huge dataset on particulate and gaseous pollutants, health outcomes, social, economic and behavioural information, collected simultaneously in an area close to the city centre and in a rural location during two intensive campaigns.
“Analysing this rich dataset allows us to better understand how emissions, chemistry and meteorology interact to determine pollution levels during winter haze events and summer smogs and gauge their impact on physical and mental health.
“The programme has enhanced UK-China collaboration, trained the next generation of scientists, and created a legacy of enhanced scientific understanding for the future that will help citizens to take individual actions to improve their day-to-day lives.”
Whilst Birmingham environmental scientists played a pivotal role in the programme, the project’s greatest strength came from the close partnership between Chinese and British scientists. More than 150 experts from 11 Chinese and 18 British research institutions worked together as equal partners on challenges of global significance.
The UK-China team of scientists developed a range of eight policy suggestions, based on the research, which could be taken up by policymakers. These ranged from reducing emissions of particulate matter, VOCs and black carbon from outside Beijing city centre to combating the impact of air pollution on mental health by advocating the use of face-masks and air purifiers during pollution events for people with pre-existing conditions, the elderly and the young.
“APHH-Beijing has significantly advanced our understanding of air pollution in Beijing, supporting policy development to provide widespread human health improvements across a sizable number of people living and working in Beijing,” commented Professor Roy Harrison.
“We’ve engaged with policymakers from the beginning of the programme and some of our research outcomes, such as the updated high resolution emission inventories and air pollutant emissions from residential sources, have already contributed changes in environmental policy.”
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