CHARACTERISTICS AND INFLUENCING FACTORS OF ATMOSPHERIC NH3 POLLUTION IN SHIHEZI
Atmospheric ammonia(NH3)has an important impact on the formation of secondary aerosols.To investigate the characteristics of atmospheric NH3 pollution in Shihezi,the atmospheric NH3 concentration was observed continuously from December 2020 to November 2021,and the magnitude level,variation characteristics,and influencing factors of atmospheric NH3 in Shihezi were analyzed,in combination with the characteristics of atmospheric NH3 emissions and the characteristics of concurrent meteorological parameters.The results show that the annual average concentration of atmospheric NH3 in Shihezi was 21.0 μg/m3,the average concentration of atmospheric NH3 in the four seasons ranged from 20.2 μg/m3 to 21.7 μg/m3,with a small seasonal fluctuation.In winter,the main source of atmospheric NH3 in Shihezi was the escape of ammonia during the industrial flue gas denitrification process,and the continuous low boundary layer height and low wind speed in winter led to the deterioration of atmospheric diffusion conditions.The unfavorable diffusion conditions were an important reason for the accumulation of atmospheric NH3 concentration in winter.Increasing the control of ammonia escape during flue gas denitrification was beneficial to reducing the atmospheric NH3 concentration in Shihezi.The diurnal variation of atmospheric NH3 concentration showed a pattern of higher during the day and lower at night in Shihezi in all seasons,with the daily variation of atmospheric NH3 concentration being highest in spring and lowest in winter.The atmospheric NH3 concentrations in spring and winter showed a single-peak pattern,with dual peaks at 12:00 and 16:00,respectively,and summer and autumn atmospheric NH3 concentrations showed a multi-peak pattern,with maximum peaks at 11:00 and 13:00,respectively.Compared with other cities in China,the daytime peak of atmospheric NH3 concentration in Shihezi appeared 1 to 3 hours later.The quantitative evaluation of the influencing factors of atmospheric NH3 concentration by the random forest algorithm showed that the influence of meteorological factors on atmospheric NH3 in the four seasons reached 63.6％,58.8％,73.9％,and 64.5％,respectively,and meteorological factors were the main influencing factors of atmospheric NH3 concentration.
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