[Regional Transport Matrix Study of PM_2.5 in Jingjinji Region, 2015]

By coupling particle source apportionment technology (PSAT) with a comprehensive air quality model with extensions (CAMx), the regional transport matrix of PM_2.5 was built for 13 cities in the Jingjinji Region in 2015. Results showed that the major contributor to PM_2.5 was local source emissions, contributing 21.49%-68.74%, The internal transport from in-region sources contributed 13.31%-54.62% and the external transport from out-region sources contributing 13.32%-45.02% were also significant. The spatio-temporal distribution of the PM_2.5 transport matrix was characterized by geographical, meteorological, and source patterns. Local emissions exerted the most significant impact on the central part of Jingjinji in winter, while regional transport contributed more to the southern region in other seasons. By assessing the input/output and activity of PM_2.5 transport, Langfang, Hengshui, Chengde, Qinhuangdao, and Xingtai were receptors; Tianjin, Cangzhou, Tangshan, Beijing, Shijiazhuang, and Handan were sources, and Zhangjiakou and Baoding had a balanced transportation mode. The seasonal matrix of PM_2.5 showed significant transport between Beijing and Langfang, Baoding, Chengde, Tianjin, Cangzhou, while the city list for Tianjin and Shijiazhuang differed slightly.