Chemical composition, sources, and health risks of PM in small cities with different urbanization during 2020 Chinese Spring Festival.

To investigate the impact of quarantine measures and fireworks banning policy on chemical composition and sources of PM and associated health risks in small, less developed cities, we sampled in Guigang (GG), Shaoyang (SY), and Tianshui (TS), located in eastern, central, and north-western China, in 2020 Spring Festival (CSF). Mass concentration, carbonaceous, metals, and WSIIs of PM were analyzed. The study found high levels of PM pollution with the average concentration of 168.05 µg/m in TS, 134.59 µg/m in SY, and 125.71 µg/m in GG. A negative correlation was found between the urbanization level and PM pollution. Lockdown measures reduced PM mass and industrial elements. In non-control period (NCP), combustion and fireworks were the major sources of PM in GG and TS, and industry source accounted for a significant proportion in the relatively more urbanized SY. Whereas on control period (CP), soil dust, combustion, and road dust were the main source in GG, secondary aerosols dominated in SY and TS. Our health risk assessment showed unacceptable levels of non-carcinogenic and carcinogenic risks over the study areas, despite lockdown measures reducing health risks. As and Cr(VI), as the major pollutants, their associated sources, industry sources, and fireworks sources, posed the greatest risk to people at the sampling sites after exposure to PM. This work supports the improvement of PM control strategies in small Chinese cities during the CSF.