The Meteorological Characteristics Of Air Pollution In Northern Slope Of Tianshan Mountains

Based on the environmental monitoring data(concentration of PM_2.5,PM₁₀,SO₂,NO₂,CO,O₃)and the meteorological observation data?temperature,precipitation,wind,humidity,pressure?during 2015-2018 in Urumqi-Changji-Shihezi Area on the northern slope of Tianshan Mountains,the spatial and temporal distribution characteristics of air pollutants,the relationship between pollutant concentration and meteorological factors,the pollution circulation background and the meteorological conditions of different pollution were analyzed.The results showed as follows:?1?Atmospheric pollutants had significant spatial and temporal distribution characteristics in Urumqi-Changji-Shihezi Area.60%days reached the Grade II standards in Urumqi-Changji-Shihezi Area each year.The primary pollutant was PM₁₀,next was PM_2.5.The annual pollution days were 78-126 d,and the heavy pollution days were 19-45 d,mostly occurs in the heating period.Air pollution increased in 2015-2017 and decreased in 2017-2018 in Urumqi-Changji-Shihezi Area.PM_2.5,PM₁₀,SO₂,NO₂,CO concentrations were highest in winter and lowest in summer,but O₃ concentrations were highest in summer and lowest in winter.The annual distribution of the six atmospheric pollutants showed single-peak distribution,with the peak values of PM_2.5,PM₁₀,SO₂,NO₂,CO in January to February,and the peak values of O₃ in July.The concentrations of PM_2.5,PM₁₀,SO₂,NO₂,CO increased significantly in the heating period,which were 68?g/m³,79?g/m³,8?g/m³,19?g/m³,1.0 mg/m³ higher than that in the non-heating period.The ratio of PM_2.5 to PM₁₀ in non-heating period was 0.35,but increased to 0.63 in heating period.Air pollution showed the highest in the first day,with AQI at 228,and then the fifth day of the Lunar New Year.The spatial distribution of PM_2.5 and PM₁₀ were higher in plain,lower in mountain area,higher in north area and lower in south.For SO₂ was the highest in Changji,then in the north of Urumqi.For NO₂ was the highest in the center and then the south of Urumqi.For CO was the highest in Shihezi,then in the west of Urumqi.For O₃ was the highest in Tianchi and then in Shihezi.?2?The concentration of air pollutants in Urumqi-Changji-Shihezi Area were greatly affected by the change of meteorological elements.The pollutant concentration rose when temperature under-5?,wind speed under 1.5 m/s,humidity between 60%and 80%,pressure higher than 1040 hPa,and the moderate rain could dilute the pollutants.The diffusion capacity of pollutants was enhanced when the mixing layer higher than 500m,and the ventilation coefficient greater than 1500 m/s².The PM_2.5 concentration increased when the inversion intensity greater than 5?/?100m?and the static-stability index greater than 5.The correlation coefficient between PM_2.5 concentration and air temperature was 0.734,showed the strongest correlation.The principal component of pollution obtained by the PCA method was PM_2.5,and the meteorological elements was the stability index and the precipitation index,which could be used to measure the quality of air pollution diffusion conditions.?3?Air pollution were more likely to occur under certain weather conditions in Urumqi-Changji-Shihezi Area.In spring,air pollution in Urumqi-Changji-Shihezi Area occurred when a low trough in Lake Balkhash and a cold front on the ground in Northern Xinjiang,accompanied by dust.In winter,air pollution occurred with high pressure ridge in Xinjiang,at the rear of Mongolian High,or the westerly belt,and the saddle field,accompanied by fog or smog.Persistent serious air pollution in winter occurred on500 hPa Xinjiang high ridge,weak wind in the middle-level and the back of the ground high pressure,often accompanied by long-term inversion maintenance of boundary layer,the 70%-90%humidity and wind speed under 2 m/s.When the precipitation over 1.0 mm,temperature rise,and wind speed increase,AQI in Urumqi-Changji-Shihezi area decreased.