all decreasing, especially the latter two pollutants. The variation
trends of PM
10
and PM
2.5
are fluctuating, but the overall pollution situation has been greatly improved. Besides, the six air pollutants have obvious seasonal variation characteristics. The main reason is that coal is used for heating in winter in northern China, and the air flow rate is slower than other seasons due to the phenomenon of atmospheric inversion. Besides, O
3
pollution in summer and autumn is obviously differ
I2017-2021呼和浩特空气质量状况及变化趋势分析-14009字.docx