Characteristics of regional transport during two-year wintertime haze episodes in North China megacities

摘要

A three-dimensional air quality model coupled with an on-line source-tagged module was adopted to investigate the source-receptor relationship in North China during the winter of 2017 and 2018. The total contribution of cities located along transport pathway (the "2 + 26" cities) accounts for most of the fine particulate matter (PM2.5) across this region both on average and during haze episodes. Regional joint prevention and control strategies are crucial to both routine and emergency environmental governance. Compared to primary PM2.5, secondary compounds may be transported across greater distances and impose notable effects in downstream areas. In regard to the secondary inorganic aerosols (SIA) in Beijing during haze episodes, regional transport plays a more important role than do local emissions. The contribution of the transport of particle-phase secondary pollutants is comparable to that of the transport of gas-phase precursors during haze episodes. Control measurements of gas-phase precursors in upstream areas are also important, and they benefit the reduction in the total PM2.5 level.