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<p>Secondary aerosol is a major contributor to fine particulate matter (PM<sub>2.5</sub>) air pollution in Beijing-Tianjin-Hebei (BTH) region, and the spatial and temporal variations of which in BTH was still not well known. In this study, the concentrations of Primary PM<sub>2.5</sub> (PPM) and Secondary PM<sub>2.5</sub> (SPM) in 13 cities of the BTH regions were divided and qualified using the approximate envelope method (AEM) from March 2017 to February 2023, and the long-term trends and drivers of PPM and SPM were discussed. Over the six-year period, PM<sub>2.5</sub> concentrations in the BTH region show an overall decreasing trend, but the decreasing trend has leveled off in recent years. Specifically, PPM showed a continuously and rapidly downward trend in the BTH region, with an annual reduction rate of 2.57&#xa0;µg·m<sup>− 3</sup>/year, while lower decrease trend was found for the SPM (1.96&#xa0;µg·m<sup>− 3</sup>/year). After removing the effects of seasonal and short-term meteorological factors, the results obtained using the time series decomposition better reflect the evolutionary trends of PPM and SPM, which suggested that the decline of PPM and SPM are both mainly contributed by the primary emission reduction from the south-central region of BTH during the autumn and winter seasons, although the SPM seems to also affected by the special topography that favor for the regional transport and secondary transformation of primary pollutants, thus partly explains the slowing down of the decreasing trend of PM<sub>2.5</sub> in recent years. This work provides an observation-based assessment to better understand the rapid changes in primary and secondary aerosol distributions in the BTH region.</p>

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Spatial Distribution Characteristics of Secondary PM2.5 in Beijing-Tianjin-Hebei Region Based on Time Series Decomposition

  • 期刊论文

  • 发表日期：

    2025年3月6日

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  • Qing Yao,
  • Jing Ding,
  • Zi-rui Liu,
  • Xu Yang,
  • Ying-xiao Tang,
  • Zi-yin Cai,
  • Su-qin Han

摘要

Secondary aerosol is a major contributor to fine particulate matter (PM2.5) air pollution in Beijing-Tianjin-Hebei (BTH) region, and the spatial and temporal variations of which in BTH was still not well known. In this study, the concentrations of Primary PM2.5 (PPM) and Secondary PM2.5 (SPM) in 13 cities of the BTH regions were divided and qualified using the approximate envelope method (AEM) from March 2017 to February 2023, and the long-term trends and drivers of PPM and SPM were discussed. Over the six-year period, PM2.5 concentrations in the BTH region show an overall decreasing trend, but the decreasing trend has leveled off in recent years. Specifically, PPM showed a continuously and rapidly downward trend in the BTH region, with an annual reduction rate of 2.57 µg·m− 3/year, while lower decrease trend was found for the SPM (1.96 µg·m− 3/year). After removing the effects of seasonal and short-term meteorological factors, the results obtained using the time series decomposition better reflect the evolutionary trends of PPM and SPM, which suggested that the decline of PPM and SPM are both mainly contributed by the primary emission reduction from the south-central region of BTH during the autumn and winter seasons, although the SPM seems to also affected by the special topography that favor for the regional transport and secondary transformation of primary pollutants, thus partly explains the slowing down of the decreasing trend of PM2.5 in recent years. This work provides an observation-based assessment to better understand the rapid changes in primary and secondary aerosol distributions in the BTH region.