[Pollution Characteristics and Influencing Factors of PM_2.5 in Shanxi Province Based on Wavelet Transform]

Based on the daily average concentration of PM_2.5, social influencing factor data, and meteorological data of 11 cities in Shanxi Province from 2015 to 2019, the concentration period of PM_2.5 was determined using wavelet transform. The correlation between PM_2.5 and social influencing factors and meteorological factors was explored respectively through Spearman correlation and the wavelet coherence spectrum, and the main influencing factors of long-term and short-term management and control of PM_2.5 were determined. The results showed that the concentration of PM_2.5 in Shanxi Province showed an upward trend from 2015 to 2017, with an average annual increase rate of 4.3% and a downward trend from 2018 to 2019, with an average annual decrease rate of 4.2%. The average concentration of PM_2.5 showed a "U" distribution, with the highest value in January (95 μg·m^-3) and the lowest in August (34 μg·m^-3); the average value in winter was approximately twice that in summer. The ρ(PM_2.5) in southern cities such as Linfen was 62 μg·m^-3, and the average value in Datong and other northern cities was 45 μg·m^-3, which was high in the south and low in the north. There were significant periodic changes in PM_2.5 concentration in the 11 cities, including a long period of approximately 293 d and a short period of approximately 27 d. Among them, the energy consumption level and industrial structure were the strong driving factors affecting the PM_2.5 concentration in the long period of Shanxi Province. In the short period, it was greatly affected by the change in atmospheric circulation, and different cities were affected by typical meteorological factors. Linfen, Yuncheng, Datong, Shuozhou, and Xinzhou were vulnerable to wind speed; Jinzhong and Luliang were vulnerable to temperature; and Taiyuan, Jincheng, Yangquan, and Changzhi were uniquely and significantly affected by relative humidity. Therefore, industrial structure adjustment and energy structure adjustment are key to the long-term control of atmospheric PM_2.5 and the long-term improvement of air quality in Shanxi Province. The differential impact of different urban meteorological factors on PM_2.5 should be considered when carrying out short-term regional joint prevention and control.