Detection of historical changes and trends of air quality is very beneficial in understanding the potential effect of past, current and future changes. In order to explore the changes in air quality under the combined influences of human activities and different dry and wet meteorological conditions in China, this paper adopts the air pollution index (API) method to reduce the dimensions of such data as SO₂, NO₂ and PM₁₀ monitored in 86 major cities each day. The changes of the air quality are analyzed in different time scales (dry season, rainy season and annual scale). Besides, a classification principle of air quality types is proposed in order to reveal the distribution characteristics of air quality types under different spatial and temporal conditions. The results show that: (i) the numbers of cities with improved air quality in China account for 62.8%, 48.8% and 57%, respectively, of the 86 cities in the annual scale, rainy season and dry season. (ii) The air quality fluctuates greatly in the dry season, while the improvements in air quality are gradually less significant from North China and Northwest China to their surrounding areas. (iii) China's air quality shows significant differences in different time scales. The total number of poor-quality type and slight-pollution type took up 56.98%, 65.11% and 24.42%, respectively, in the annual scale, in the dry season and rainy season. However, no poor-quality type is found in the rainy season. The characteristics and types of spatial and temporal changes in air quality revealed by the results can provide relevant useful information for air-quality managers based on various regions and time.

Zhihua Zhu. Temporal and spatial variation characteristics of air quality trends in China. Academic Journal of Environment & Earth Science (2023) Vol. 5 Issue 7: 1-12. https://doi.org/10.25236/AJEE.2023.050701.

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