To study winter pollution characteristics and physicochemical properties of PM2.5 in a northwest industrial city, for example, Baiyin in Gansu Province, we used related instruments, such as single particle aerosol mass spectrometry to conduct real-time online PM2.5 chemical composition observations, compared with Lanzhou in the same period. The results showed that, during the observation, PM2.5 concentrations (44.89 μg·m-3) in Baiyin were significantly lower than the same period in Lanzhou (70.69 μg·m-3). However, the proportion of particles containing heavy metals (7.84%) was significantly higher than that of Lanzhou (2.92%), the chemical composition was complex, and PM2.5 was mainly contributed by particles with larger particle sizes. The particle size distribution range of Cu, Pb, and Zn particles in Baiyin was relatively wide, the number of Cu and Zn particles was higher, and the mixing ratio of particles was higher than in Lanzhou. The main pollution source was automobile exhaust 30.91% and a secondary inorganic source was 13.00%. The pollution event on January 4, 2020 was mainly caused by the increased contributions of automobile exhaust and secondary inorganic sources, and the poor meteorological diffusion conditions in the early stage. The control of PM2.5 pollution in Baiyin in winter should be dominated by emission reduction of automobile exhaust and secondary inorganic sources, and control of heavy metal pollution in the atmosphere should be strengthened.
Keywords: PM2.5; chemical composition; heavy metal; industrial city; mixing state.