Group 1 - The air quality in Beijing is currently at a moderate pollution level, primarily due to PM2.5, with similar pollution observed in eastern China [1] - Since December 14, air quality has deteriorated in the Beijing-Tianjin-Hebei region and surrounding areas due to reduced wind, increased humidity, and temperature inversions [1][2] - The current pollution process is attributed to unfavorable meteorological conditions combined with high emissions from various industries, leading to the accumulation and transformation of pollutants [2] Group 2 - In the Beijing-Tianjin-Hebei region, the activity level in the thermal power and heating sector has increased by approximately 20 percentage points compared to pre-heating season levels [2] - Key industries such as steel, petrochemicals, and construction are maintaining high operational levels, contributing to persistent PM2.5 pollution [2] - The proportion of nitrates in PM2.5 has exceeded 30%, indicating that emissions from key industries and diesel vehicles are significant contributors to pollution [2] Group 3 - In response to the pollution, 86 cities in the Beijing-Tianjin-Hebei, Yangtze River Delta, and central Yangtze River regions have activated early warning responses [2] - Specific measures include differentiated control strategies for industrial enterprises based on environmental performance, such as production halts and emission limits [2] - In Hubei province, nitrogen oxide emissions from industrial sources decreased by 10.1% as part of the coordinated response to pollution [3] Group 4 - Air quality in cities like Ezhou, Xiangyang, and Suizhou improved from heavy to moderate pollution levels by December 18 [3] - Public health recommendations include minimizing outdoor activities and using public transportation to reduce traffic emissions during poor air quality [3] - Air quality is expected to gradually improve in the Beijing-Tianjin-Hebei region starting December 20, with further improvements in the Yangtze River Delta and central Yangtze River regions on December 21 [3]