China focuses on improving air quality via the coordinated control of fine particles and ozone

Fine particulate matter, referred to as PM2.5, and ground-level ozone (O3) are the main pollutants degrading the air quality of China’s cities and wider urban regions. Both have serious human health effects, such as heart disease, asthma, and lung damage.

The World Health Organization (WHO) provides clear guidelines regarding acceptable concentrations of PM2.5 and O3. However, despite some success in lowering PM2.5 levels following certain policy implementations, O3 levels in China have continued to rise, and not one city in China is meeting the WHO's targets for either of these two pollutants.

The ways in which PM2.5 and O3 are formed in the lower atmosphere are intricately linked, sharing common precursor compounds. In addition, once formed, the two pollutants interact with each other via various atmospheric pathways.

Much progress has been made in China to understand the sources of PM2.5 and O3 and how their concentrations vary in the air breathed by its urban populations. Nevertheless, many challenges and gaps in knowledge remain.

One clear message cutting through from scientists is that, rather than focusing separately on either PM2.5 or O3, coordinating their control is central to further improving China’s air quality. The approach is, quite literally, a breath of fresh air.

This special issue of Atmospheric and Oceanic Science Letters was organized to address the major scientific challenges that remain in  understanding the chemical and physical processes that contribute to the formation of PM2.5 and O3. In doing so, the door is then opened to developing strategies and policies towards their coordinated control and, ultimately, better air quality for China's urban populations.

"The issue is structured according to several different key themes", explains Prof. Likun Xue, a scientist based at Shandong University and one of the three Editors of the special issue. "There are papers on the spatiotemporal variability of PM2.5 and O3 pollution, the effects of heatwaves, the chemical mechanisms and sources of precursor compounds, and even the development of a new instrument for measuring O3 and its precursors".

Taking one of those themes as an example, like many forms of extreme weather, heatwaves are becoming more frequent and severe under climate change. This has a tangible impact on O3 pollution because of its temperature-driven chemical production. This link underscores the need for improved strategies to manage O3 as part of efforts to mitigate the effects of future climate change.

Overall, this special issue offers valuable insights into our current understanding of the elaborate mix of factors that interact to ultimately determine the formation and patterns of these two key air pollutants in urban China.

"Moving forward, the coordinated control of PM2.5 and O3 will be a critical part of China's efforts to reduce pollution and mitigate carbon under the country's 'Carbon Neutrality' framework," concludes Prof. Xue.

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