Core Viewpoint - The PM2.5 pollution in the Beijing-Tianjin-Hebei region and surrounding areas has intensified since October 23, with a significant increase in pollution levels due to high emissions and adverse meteorological conditions [1][2][3]. Group 1: Pollution Trends - The region experienced a transition from "good air quality" to the first regional PM2.5 pollution event of the autumn-winter season, with PM2.5 concentrations peaking at 123 micrograms per cubic meter in Baoding on October 25 [2][5]. - The pollution spread from northern Henan to cities along the Taihang Mountains, with Baoding and Langfang reaching moderate pollution levels [2][3]. - As of October 28, the hourly PM2.5 concentration in Hebi reached 174 micrograms per cubic meter, indicating severe pollution [2][3]. Group 2: Causes of Pollution - High levels of regional pollution emissions have been maintained, with heavy-duty truck traffic increasing by 6% compared to the previous year, and 253 fire points detected in the region [3][4]. - The composition of PM2.5 during high pollution periods showed that over 40% was nitrate, indicating that industrial and diesel vehicle emissions are significant contributors [3][4]. Group 3: Meteorological Conditions - Adverse meteorological conditions, including stagnant air, high humidity, and temperature inversions, have exacerbated pollution levels, leading to a "cumulative - brief relief - intensification" pattern [4][5]. - The region experienced weak southerly winds and high relative humidity, which contributed to the accumulation of pollutants [4][5]. Group 4: Future Outlook - Air quality is expected to gradually improve starting October 30, with cities in the region implementing pollution alerts and control measures [5][6]. - The forecast indicates that from October 30 to November 2, air quality will improve to good levels due to the influence of cold air [6].