- 1Nanyang Institute of Technology, Nanyang, China (wangwn@nyist.edu.cn)
- 2Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands.
- 3Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China.
- 4National Meteorological Information Center, China Meteorological Administration, Beijing, China.
China is a significant region for crop cultivation. For a long time, there has been a common practice of burning crop residues during the post-harvest period (from May to October). The smoke emitted from straw burning contains both types of ozone precursors, including nitrogen oxides (NOx=NO+NO2) and volatile organic compounds (VOCs), and can be transported over long distances. During the transport process, secondary formation or consumption of ozone precursors occurs within the smoke plumes. After the smoke plume mixes with the atmosphere in the downwind urban area, it will lead to changes in the local ozone formation sensitivity. However, due to the nonlinear relationship between ozone and its precursors, the changes in ozone levels in downwind cities are not as straightforward as expected.
Here, we explore the temporal evolution of urban ozone and its precursors on smoke-affected days using multi-source satellite-derived fire event tracking datasets, which are screened by a semi-quantitative absorbing aerosol index (AAI), tropospheric NO2 and HCHO columns measurements from OMI, fire points from Himawari-8, and ground-level O3 monitoring dataset. We aimed to understand the associations between urban ground-level O3 concentrations and crop residue burning events in China. Our analysis revealed that no consistent changes were shown in urban O3 on smoke-affected days. In addition, there was an increase in NO2, while HCHO and O3 decreased in cities after mixing with smoke that had taken a long transport time. Our findings suggest that the O3 formation sensitivity within aged smoke tends to be controlled by VOC-limited regime. We hypothesize that the large amount of NOx carried by aged smoke consumes urban VOCs and O3, while producing NO2 locally. When fresh smoke, which is mainly controlled by the NOx-limited regime, enters urban environments rich in NOx, it leads to an increase in O3 concentration. Our analysis may contribute to an improved understanding of the influence of straw burning on urban ozone levels in China.
How to cite: Wang, W., van der A, R., Ding, J., Cheng, T., and Wang, C.: Exploring the effect of straw burning on urban ozone levels based on multi-source satellites in northern China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1314, https://doi.org/10.5194/egusphere-egu25-1314, 2025.
