Mixed and intensive haze pollution during the transition period between autumn and winter in Beijing, China

In the Northern China Plain (NCP), extreme haze events with high concentrations of fine particles occur frequently during the winter but rarely occur in autumn. In this study, we present a synthetic analysis of particulate constituents during the historically polluted transition period of autumn–winter in 2018, revealing that mixed-type haze episodes are the result of regional transport, homogeneous/heterogeneous conversion, and sandstorm...