为何秋冬季易发生PM2.5污染过程？

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].