Characterization of the Air Quality Index for Urumqi and Turfan Cities, China

This study investigated the atmospheric PM2.5, PM10, SO2, NO2, CO, and O3 in Urumqi and Turfan cities from 2015 to 2017. In addition, six AQI categories and AQI values and seasonal changes in the major pollutants in Urumqi and Turpan were studied. In the three-year (2015–2017) study, in Urumqi, the average proportion of grades I, II, III, IV, V, and VI in spring were 16.3%, 59.7%, 16.0%, 5.33%, 2.67%, and 0%, respectively, were 12.0%, 82.7%, 5.33%, 0%, 0%, and 0% in summer; were 13.3%, 65.7%, 16.3%, 3.33%, 1.33%, and 0% in fall, and were 0.667%, 14.3%, 22.3%, 15.3%, 33.7%, and 13.7% in winter. In the Turpan region, the mean proportion of Grade I, II, III, IV, V, and VI pollutants were 0%, 61%, 21.3%, 8.00%, 2.33%, and 7.33% in spring, respectively; were 0.67%, 74.7%, 20.0%, 2.00%, 0.67%, and 2.00% in summer, were 1.33%, 59.7%, 42.3%, 7.67%, 0.33%, and 2.00% in fall, and were 0%, 11.0%, 35.3%, 29.3%, 20.3%, and 4.00% in winter. In the three-year (2015–2017) study, based on the results of the survey, it was determined that two cities have the best air quality in summer and the worst air quality in winter. In Urumqi, when the AQI was between 101–150, the main air pollutants in 2015 were PM2.5 and PM10. In 2016, the main air pollutant was PM2.5, and in 2017, the main air pollutants were PM2.5 and PM10. In Turpan, the main air pollutants in 2015 were PM2.5 and PM10, were PM2.5, PM10, and O3 in 2016, and was PM10 in 2017. When the AQI was between 151 and 200, in Urumqi, the main atmospheric pollutant in the three-year period was PM2.5. In Turpan, the main atmospheric pollutants in the three-year period were PM2.5 and PM10. When the AQI was between 201 and 300 in Urumqi, PM2.5 was the main atmospheric pollutant from 2015–2017. In Turpan, the main atmospheric pollutants in the three-year period were PM2.5 and PM10. To summarize, in both Urumqi and Turpan, PM2.5 and PM10 were the most predominant air pollutants causing high AQI values. More attention should thus be paid to the sources and reduction of these pollutants.