Winter heating practices in Northern China directly linked to increased carbon air pollution

A new investigation into air quality in northern China has determined a strong connection between winter domestic heating and elevated levels of carbonaceous aerosol pollution. The study, led by researchers Yuewei Sun and Jing Chen at the State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Beijing Normal University, focused on Yuncheng, a city in the heavily polluted Fenwei Plain. The findings show that during the winter heating period, concentrations of organic and elemental carbon in fine particulate matter PM2.5 increased by over 58 percent.

A Tale of Two Cities

The research team collected and analyzed air samples in Yuncheng during the winter and summer of 2020–2021, specifically comparing the periods before and during the official domestic heating season. The mass concentrations of both PM2.5 and its carbon components were substantially enhanced once heating began. In contrast, a parallel investigation in Beijing during the same period showed no significant difference in pollution levels before and during its heating season. This difference is attributed to Beijing's complete transition from coal to natural gas for its central heating systems.

Identifying the Primary Source

Using a technique called positive matrix factorization, the scientists identified the specific sources of carbon pollution. In Yuncheng, emissions related to heating, such as residential coal combustion and biomass burning, were the dominant source of carbonaceous aerosols during the heating period, accounting for 50.9 percent of the total. This contribution rose to over 55 percent on the most polluted days. This finding confirms that how residents heat their homes is a major factor in the city's winter air quality.

Seasonal Shifts in Pollution Drivers

The study also revealed a clear seasonal change in the main sources of air pollution. While winter pollution was driven by heating, summer pollution in Yuncheng had different origins. During the warmer months, vehicular emissions, particularly from diesel engines, became the largest contributor at 49.6 percent. Secondary formation, a process where chemicals in the atmosphere react to form new particles, was another significant source in the summer, contributing 30.3 percent.

Pollution on the Move

The unique basin topography of Yuncheng often traps air pollutants, but the problem is not entirely local. The researchers used potential source contribution function analysis to track the movement of air masses. They found that during the heating period, carbonaceous aerosols were transported to Yuncheng from a large area to the northwest, including central Shaanxi province. This indicates that both local emissions and regional transport from widespread heating activities contribute to the city's severe winter air pollution.

A Blueprint for Cleaner Air

The noticeable difference in winter air quality between Yuncheng and Beijing demonstrates the effectiveness of clean energy policies. While Beijing's population and economic output are much larger than Yuncheng's, its air pollutant levels except for NO₂ were considerably lower due to the successful implementation of its Clean Air Action Plan. The researchers note that this "coal-to-gas" transition offers a clear path forward for improving air quality across northern China.

Policy and Economic Considerations

The authors conclude that promoting a transition to cleaner residential heating in Yuncheng and other similar cities would produce substantial environmental benefits. They acknowledge the economic challenges that less developed cities face in making such a transition. The study suggests that local heating policies should be developed based on economic conditions and consider factors like energy accessibility and affordability to ensure a successful and sustainable shift away from traditional coal and biomass burning for a healthier environment.

Corresponding Author:

Jing Chen

Original Source:

https://doi.org/10.1007/s44246-023-00078-w

Contributions:

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Yuewei Sun, Ke Xin, Jing Ai, Huiying Huang, Lingyun Zhang, Weihua Qin and Qing Yu. Research supervision and conceptualization were performed by Jing Chen. The first draft of the manuscript was written by Yuewei Sun and Jing Chen, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.