Air pollution characteristics, health risks, and typical pollution processes in autumn and winter in a central city of China

By combining atmospheric environment observational data, we expounded the characteristics, types, and potential source regions of air pollution in Zhengzhou using the characteristic radar chart, potential source contribution factor analysis, and concentration weighted trajectory analysis. We also calculated the excess risk (ER) of death caused by excessive air pollutants and explored a typical pollution process. The results showed that the average PM_2.5 concentration in autumn (October and November 2020) (55.5 μg/m³) was lower than that in winter (December 2020 and January 2021) (83.5 μg/m³), and January was the month most seriously affected by dust pollution. Secondary pollution was mainly concentrated in December and January, while dust pollution was mainly concentrated in October and January. Dust pollution was mainly affected by long-distance transport in the northwest, and the remaining pollution (except comprehensive pollution) was mainly affected by short-distance transport in the eastern cities (Jining and Xuzhou). The ER values were mainly attributed to excessive PM₁₀, PM_2.5, and NO₂. Secondary pollution and dust pollution were the main contributors to ER. During the typical pollution process, in the dust period (stage I), air masses were mainly affected by long-distance transport in the northwest, which displayed higher wind speed and lower relative humidity. Moreover, the PM_2.5/PM₁₀ value was below 0.4. During the heavy PM_2.5 pollution period (stage III), air masses were mainly affected by local transport in the northeast, which displayed lower wind speed and higher relative humidity. This period showed clear secondary pollution and more severe motor vehicle emissions.