Abstract:
Objective To investigate spatial-temporal distribution characteristics of air quality indexes (AQI) in 113 key cities for environmental protection in China.
Methods We collected daily AQI data and the concentration data on primary air pollutants (including particulate matter less than 2.5 microns in aerodynamic diameter PM
2.5,particulate matter less than 10 microns in aerodynamic diameter PM
10,sulfur dioxide SO
2,nitrogen dioxide NO
2carbon monoxide CO,and ozone O
3) from the 113 key environmental protection cities in China in 2014,and the spatio-temporal variation of air quality in the cities was analyzed.
Results In 2014,the air quality in the cities was the worst in the winter but the best in the summer.In the spring,the proportions of the days with PM
10 as a primary air pollutant were 60.0%,81.8% and 100.0% for the cities in North,Northeast,and Northwest China;in the summer,the proportions of the days with O
3 as a primary air pollutant were 54.6%,68.8%,27.3%,and 40.0% for the cities in Northeast,East,South,and Southwest China;the proportions of the days with PM
2.5 as a primary air pollutant were 93.8% and 81.8% for the cities in Central and Northeast China in the autumn and 100.0% and 96.9% for the cities in Northeast and East China in the winter.The regional air quality was gradually improved from the central regions (Beijing-Tianjin-Hebei province,Henan province,and Shandong province) to their surrounding cities.In 2014,the proportion of the days with good or excellent air quality (AQI ≤ 100) varied from 87.74% to 52.47% among all the cities and ranged in a decreased sequence for the cities in the South (83.74%),Southwest (78.56%),Northeast (68.24%),Northwest (67.23%),East (65.06%),Central (55.34%),and North China (52.47%).
Conclusion In the year 2014,PM
2.5 was still the primary air pollutant in China.Apart from controlling PM
2.5 pollution,we should also pay close attention to the control of PM
10 in the North cities in spring and O
3 in the cities in the Northwest,East,South,and Southwest China in summer.