COVID-19管控前后不同污染阶段PM2.5中二次无机离子变化特征

为探讨新冠肺炎疫情(COVID-19)管控前后不同污染阶段PM_2.5中二次无机离子变化特征，使用高分辨率(1 h)在线仪器对2019年12月15日至2020年2月15日郑州冬季气象、污染气体浓度和PM_2.5中水溶性离子水平进行在线监测，分析此次COVID-19管控前后霾过程的成因、大气污染物的日变化特征和在霾不同阶段下大气污染物的分布特征.结果表明，郑州主要受到高压脊控制，天气形势稳定，有利于大气污染物累积，二次无机气溶胶(SNA,包括SO₄^2-、NO^-₃和NH⁺₄)是水溶性离子的主要组分，占比高达90%以上，COVID-19期间居家隔离措施对霾不同阶段下大气污染物的分布特征产生不同的影响，COVID-19期间PM_2.5在干净、发生和消散阶段的浓度比COVID-19前有所提高，但是发展阶段明显降低，居家隔离明显使PM_2.5高值降低了；NO₂、SO<...

Changes in Secondary Inorganic Ions in PM2.5 at Different Pollution Stages Before and After COVID-19 Control

To investigate the change characteristics of secondary inorganic ions in PM_2.5 at different pollution stages before and after COVID-19, the online monitoring of winter meteorological and atmospheric pollutant concentrations in Zhengzhou from December 15, 2019 to February 15, 2020 was conducted using a high-resolution (1 h) online instrument. This study analyzed the causes of the haze process of COVID-19, the diurnal variation characteristics of air pollutants, and the distribution characteristics of air pollutants at different stages of haze.The results showed that Zhengzhou was mainly controlled by the high-pressure ridge during the haze process, and the weather situation was stable, which was conducive to the accumulation of air pollutants. SNA was the main component of water-soluble ions, accounting for more than 90%. Home isolation measures during COVID-19 had different impacts on the distribution characteristics of air pollutants in different haze stages. After COVID-19, the concentration of PM_2.5 in the clean, occurrence, and dissipation stages increased compared with that before COVID-19 but significantly decreased in the development stage. The home isolation policy significantly reduced the high value of PM_2.5. The concentrations of NO₂, SO₂, NH₃, and CO were the highest in the haze development stage, showing a trend of first increasing and then decreasing. The concentration of O₃ was lowest in the pre-COVID-19 development stage but highest in the post-COVID-19 development stage. The linear correlation betweenNH₄⁺]/SO₄^2-] andNO₃^-]/SO₄^2-] at different time periods before and after COVID-19 was strong, indicating that the home isolation policy of COVID-19 did not change the generation mode of NO₃^-, and the corresponding reaction was always the main generation mode of NO₃^-. The correlation betweenexcess-NH₄⁺] andNO₃^-] was high in different periods before COVID-19, and NO₃^- generation was related to the increase in NH₃ or NH₄⁺ in the process of PM_2.5 pollution in Zhengzhou.