[Characteristics of Secondary Inorganic Ions in PM and Its Influencing Factors in Summer in Zhengzhou].

Nitrate (NO), sulfate (SO), and ammonium (NH) are important components of PM, and studying their characteristics and influencing factors is essential for the continuous improvement of air quality. A series of online instruments were used to analyze the chemical components of PM in Zhengzhou in the summer of 2020. The results showed that the average (PM) was (28 ±13) μg·m, showing a daily variation characteristic of high at night and low during the day. The main concentrations of NO, SO, and NH were (7.8 ±6.7), (7.2 ±3.7), and (5.5 ±3.1) μg·m, accounting for 22%, 21%, and 16% in PM, respectively. The proportions of NO (27%) and SO (23%) in PM, respectively, increased with the increase in PM and O concentration. In addition, the proportions of NO and NH increased under low wind speed, high humidity, low temperature, and rainfall conditions. Moreover, the proportion of NO showed a daily variation characteristic of high at night and low during the day, whereas the opposite was true for SO. The gas-particle partitioning process of NHNO was the main factor affecting the concentrations of NO and NH in PM. Low temperature, high humidity, and high aerosol water content concentrations favored the partitioning of HNO and NH to the particulate phase. High pH also favored the partitioning of gas-phase HNO to NO; however, it was not conducive to the partition of NH to NH. These trends partially explained the increase in the concentration and proportion of NO in PM under different scenarios.