京津冀空气污染过程仍在持续，三大原因导致本轮污染

Group 1 - The air pollution process in the Beijing-Tianjin-Hebei region and surrounding areas is ongoing, with PM2.5 levels worsening, reaching moderate to heavy pollution levels in central Beijing-Tianjin-Hebei [1] - On November 4, 15 cities in the region experienced light PM2.5 pollution days, with Beijing's PM2.5 concentration rapidly increasing from the early hours of November 5, peaking at 163 micrograms per cubic meter, indicating short-term heavy pollution [1] - Meteorological conditions such as weak southeast winds, ground inversion, and high humidity fog are contributing to the pollution, with relative humidity exceeding 90%, which promotes the chemical transformation of pollutants [1] Group 2 - The intensity of pollutant emissions in the region remains high, with nitrogen oxides and other gaseous pollutants undergoing significant secondary transformation under humid conditions, exacerbated by ongoing heating and high levels of vehicle and machinery activity [2] - During high pollution periods, nitrate compounds dominate the particulate matter composition in Beijing, accounting for 51.8% of the total [2] - Pollution transport from northern Anhui, where straw burning has been prevalent, has also contributed to the increased PM2.5 levels in the Beijing-Tianjin-Hebei region [2] Group 3 - Forecasts indicate a slight alleviation of pollution in the northern region from November 6 to 7, with a systematic improvement expected from November 8 to 12 [2] - Air quality in Beijing is expected to gradually improve over the next two days, with a complete turnaround anticipated by November 9 [2]