Significantly alleviated PM2.5 pollution in cold seasons in the Beijing-Tianjin-Hebei and surrounding area: Insights from regional observation - Yangxi Chu; Xiyuan Chi; Jinhong Du; Jingchun Duan; Chak K. Chan; Keding Lu; Lina Yin; Jihua Tan; Jingnan Hu; Fahe Chai (Atmospheric Research, 2024)