Spatiotemporal variations of PM2.5 and PM10 concentrations between31 Chinese cities and their relationships with SO2,NO2,CO and O3

The variations of mass concentrations of PM,PM,SO,NO,CO,and Oin 31 Chinese provincial capital cities were analyzed based on data from 286 monitoring sites obtained between March 22,2013 and March 31,2014.By comparing the pollutant concentrations over this length of time,the characteristics of the monthly variations of mass concentrations of air pollutants were determined.We used the Pearson correlation coefficient to establish the relationship between PM,PM,and the gas pollutants.The results revealed significant differences in the concentration levels of air pollutants and in the variations between the different cities.The Pearson correlation coefficients between PMs and NOand SOwere either high or moderate(PMwith NO:r=0.256-0.688,mean r=0.498;PMwith NO:r = 0.169-0.713,mean r = 0.493;PM2.5 with SO:r= 0.232-0.693,mean r=0.449;PMwith SO:r = 0.131-0.669,mean r=0.403).The correlation between PMs and CO was diverse(PM:r = 0.156-0.721,mean r=0.437;PM:r=0.06-0.67,mean r= 0.380).The correlation between PMs and Owas either weak or uncorrelated(PM:r--0.35 to 0.089,mean r=-0.164;PM:r=-0.279 to 0.078,mean r=-0.127),except in Haikou(PM2.5:r=0.500;PM:r-0.509).