Abstract:

 Using the air pollutants’ concentration data at 6 monitoring points of Yinchuan and the corresponding meteorological data in 2013, characteristics of the air pollutants’ concentrations and its relationship with the meteorological conditions were analyzed. The results show that annual average PM₁₀ and PM_2.5 concentration are 0.7 times and 0.4 times greater than the standard value. Annual mean SO₂ and NO₂ concentrations both exceed in a certain degree, while CO and O₃ do not exceed the standard values. Concentrations of SO₂, NO₂, PM₁₀, PM_2.5 and CO are high in January, February, November and December, while that of O₃ is high in May and October. There are two high peaks a day for SO₂, NO₂, PM₁₀, PM_2.5 and CO concentrations in one day, i.e. from 09:00 to 12:00 and from 21:00 to 00:00. However, the maximum O3 concentration generally occurs at 15:00. All pollutants concentrations generally show a seasonal quasi 7-day cycle and a yearly quasi 30-day cycle. Frequency of air quality with good grade accounts for 56 %, while those with light pollution and excellent air quality are 26 % and 12 % respectively. The primary pollutants are PM₁₀, PM_2.5 and SO₂. Wind speed has a significant negative correlation with SO₂, NO₂ and CO concentrations, while it has a significant positive correlation with O3 concentration. Effect of wind speed on PM₁₀ and PM_2.5 concentrations is complex. When wind speed is less than a certain value, it is beneficial to PM₁₀ and PM_2.5 diffusion. On the other hand, when wind speed reaches a certain level, it can lead to increase concentrations of PM₁₀ and PM_2.5. Precipitation has good cleanup effect for pollutants, especially for SO₂, while it had a weak effect on O₃.

Key words: Yinchuan, Air pollutant concentration, Meteorological condition