Coordinated Control of PM_2.5 and O₃ and Its Impacts in China

Fine particulate matter (PM_2.5) and surface ozone (O₃) pollution have become two of the most important challenges facing air quality improvement in China. Although strict emission control policies have substantially reduced PM_2.5 concentrations in recent years, O₃ pollution has emerged as a major obstacle to achieving further improvements in atmospheric environmental quality [1]. The formation of O₃ is governed by complex nonlinear photochemical processes involving precursor emissions, meteorological conditions, and regional transport [2]. Meanwhile, interactions between PM_2.5 and O₃ further increase the difficulty of coordinated pollution control [3]. Beyond impacts on air quality, PM_2.5 and O₃ pollution poses significant threats to human health, ecosystems, agricultural productivity, and sustainable development [4].

In this context, this Special Issue of Atmosphere entitled “Coordinated Control of PM_2.5 and O₃ and Its Impacts in China” provides a comprehensive collection of recent advances regarding the characteristics, mechanisms, and impacts of PM_2.5 and O₃ pollution in China. This Special Issue focuses on pollution sources, chemical mechanisms, health effects, environmental impacts, and monitoring and assessment approaches, aiming to promote a deeper understanding to guide coordinated air pollution management strategies. This Editorial summarizes the major contributions of the studies included in this Special Issue, identifies current knowledge gaps, and discusses future research priorities.

The papers included in this Special Issue provide important insights into the characteristics of the evolution and impacts of PM_2.5 and O₃ pollution from multiple perspectives. In the Yangtze River Delta, researchers investigated compound PM_2.5–O₃ pollution events during 2015–2024 using directed event-scale synchronization networks. The results revealed that compound pollution exhibited substantial temporal evolution and spatial connectivity, with pollution linkages among cities influenced by economic development, industrial structure, and regional interactions. These findings highlight that PM_2.5–O₃ pollution is not simply a co-occurring phenomenon but a complex regional network process requiring coordinated governance.

Another study explored the spatial correlation network of PM_2.5 pollution across China, showing that geographical proximity, industrial structure, vehicle ownership, and environmental regulation jointly shaped inter-regional pollution relationships. These results emphasize the importance of regional cooperation and integrated management in controlling air pollution. In addition, other researchers in this Special Issue investigated the ecological impacts and formation mechanisms of O₃ pollution. In southwestern China, researchers quantified O₃-induced forest losses and revealed substantial impacts on ecosystem productivity and economic benefits, indicating that elevated O₃ exposure may threaten ecological stability and carbon sequestration capacity. Another study demonstrated that stratospheric intrusion can considerably enhance surface O₃ concentrations in high-altitude urban areas, highlighting the importance of considering anthropogenic emissions and natural atmospheric processes in O₃ pollution assessment.

The health and agricultural consequences of O₃ pollution were further examined. A nationwide assessment quantified the impacts of surface O₃ exposure on human health and crop production, showing that long-term O₃ exposure was associated with considerable health burdens and that elevated O₃ concentrations caused serious yield losses in winter wheat and single rice. These findings demonstrate the necessity of implementing targeted O₃ control strategies in densely populated and major agricultural regions to protect public health and food security. Moreover, an evaluation of emission reduction measures during the 2023 Asian Games in Hangzhou indicated that O₃ remained an important contributor to health risks despite temporary air quality management actions, further demonstrating the complexity of multi-pollutant control.

Despite considerable progress, several knowledge gaps remain. First, more comprehensive source apportionment studies are needed to clarify the contributions of different emission sectors and environmental factors to compound PM_2.5–O₃ pollution [5]. Second, regional transport mechanisms and intercity interactions require further investigation to support effective cooperative control strategies [6]. Finally, the impacts of climate change on future PM_2.5 and O₃ pollution evolution remain uncertain, requiring integrated modeling approaches [7].

Future studies should focus on developing multidisciplinary frameworks that combine atmospheric observations, chemical transport models, climate projections, and health and ecological assessments [8]. Long-term monitoring networks and advanced evaluation methods are also essential for furthering our understanding of pollution trends and assessing the effectiveness of control policies [9,10].

In conclusion, this Special Issue provides valuable insights into the characteristics, mechanisms, and impacts of PM_2.5 and O₃ pollution in China. The included studies advance scientific understanding of coordinated pollution control and provide support for increasing air quality, protecting public health, and promoting sustainable environmental development.