11月2日起，扩散条件转不利，区域污染持续积累升高。3日夜间，太行山前邯郸-石家庄-邢台-保定一 线，PM2.5达到良-轻度污染水平；4日在偏南风下，区域污染范围向北扩大并加重，4日夜间京津冀多 个城市达到轻度-中度污染水平。在此期间，北京PM2.5浓度逐渐升高，2日上午仍为个位数，至5日凌 晨上升至3级轻度污染水平。 气象条件偏不利，导致污染持续积累、传输。过程前期2-3日，区域受东部高压后部作用，地面大范围 偏南风，且出现较强的逆温，导致污染发生积累，并在南风下沿太行山向北传输。过程中期4-5日高压 系统减弱，区域进入低压系统控制，尤其是5日区域出现大雾天气，边界层低至300米，扩散条件较前期 进一步转差，高湿静稳条件下，颗粒物二次反应加强，导致PM2.5污染加重。 PM2.5组分中硝酸盐、均氯离子、有机物明显上升，区域燃烧源和二次源贡献突出。在北京PM2.5浓度 抬升期间，城区站点一二次组分浓度均同步上升，一次组分中钾离子、氯离子上升2-4倍，体现区域生 物质燃烧源影响；二次组分中硝酸盐也增加1倍，硝酸盐/硫酸盐比值上升，体现区域传输叠加二次转化 影响共同推动PM2.5持续升高。 最新预报显示，6-7日 ...

Core Viewpoint - The recent PM2.5 pollution event in the Beijing-Tianjin-Hebei region is attributed to adverse meteorological conditions and local pollution accumulation, with significant implications for air quality management and public health [1][2]. Group 1: Pollution Causes - The PM2.5 pollution process began on October 27 due to strong temperature inversion, high humidity, and southerly winds, leading to a rapid increase in PM2.5 levels from a good level to moderate pollution by the evening of October 28 [1][2]. - Autumn and winter seasons are prone to PM2.5 pollution due to stable weather conditions, low boundary layer heights, and increased humidity, which enhance secondary transformation reactions of PM2.5 [1][2]. Group 2: Pollution Characteristics - During the pollution event, multiple cities experienced heavy fog with visibility dropping below 200 meters, and relative humidity in Beijing approached saturation [2]. - The pollution was exacerbated by the transport of high-concentration pollution from southern regions, with over 70% of the PM2.5 contribution to Beijing attributed to regional transport [2]. Group 3: Mitigation Measures - In response to the pollution, cities in the region activated pollution alerts and implemented differentiated control measures as per the Air Pollution Prevention and Control Law [2]. - In Beijing, enforcement actions were taken to ensure construction sites manage dust pollution effectively, and transportation of construction waste was regulated to prevent spillage [2]. Group 4: Forecast and Recovery - A cold front is expected to arrive on October 31, bringing northerly winds that will improve visibility and air quality, restoring it to good levels by night [3].

Core Insights - The article discusses the recent increase in PM2.5 pollution in the Beijing-Tianjin-Hebei region and surrounding areas, highlighting the worsening air quality and the actions taken by local authorities to address the situation [1][2] Group 1: Pollution Causes - The primary reasons for the recent PM2.5 pollution include high regional emissions, with over 40% of PM2.5 consisting of nitrates, indicating significant contributions from industrial and diesel vehicle emissions [1] - Meteorological conditions such as stagnant air, high humidity, and temperature inversions have exacerbated the pollution levels, leading to a pattern of accumulation, brief relief, and intensification [1] - Local emissions combined with regional pollution have caused a rapid increase in PM2.5 concentrations in Beijing [1] Group 2: Response Measures - Cities in the Beijing-Tianjin-Hebei region have activated heavy pollution weather alerts based on air quality forecasts, implementing differentiated control measures [2] - As of the 28th, 17 cities in the region have legally initiated pollution alerts [2] - The China Environmental Monitoring Station predicts that air quality will improve in northern cities due to weak cold air from the northeast, while central and southern Hebei and northern Henan may still experience short-term moderate to heavy pollution [2]

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].