Vertical distribution characteristics of PM in the surface layer of Guangzhou

Abstract Measurements of particulate matter (PM), i.e., PM10, PM2.5, and PM1, have been performed on the Canton Tower, a landmark building in Guangzhou, at heights of 121 and 454 m since November 2010, using a GRIMM 180 aerosol particle spectrometer (Germany). Analyses of data from November 2010 to May 2013 showed that the annual average values of PM10, PM2.5, and PM1 at the observation height of 121 m above the ground were 44.1, 38.2, and 34.9 μg/m3, respectively, and those at 454 m above the ground were 35.7, 30.4, and 27.5 μg/m3, respectively. By considering the values of the secondary concentration limits given in the Ambient Air Quality Standards issued in 2012, it was observed that the annual average values of PM10 at the observation heights of 121 and 454 m, as well as those of PM2.5 at 454 m, reached those standards. Furthermore, the over-standard amplitude of the annual average value of PM2.5 at the observation height of 121 m was 9.1%. During the observation period, the maximum daily average values of PM10, PM2.5, and PM1 at the observation height of 121 m were 183.3, 144.8, and 123.8 μg/m3, respectively, and those at 454 m were 102.8, 92.7, and 86.4 μg/m3. The daily average values of PM10 at the observation height of 454 m were not above the standards. The over-standard frequencies of the daily average values of PM10 and PM2.5 at the observation height of 121 m were 0.6% and 10.7%, respectively, and the over-standard amplitudes were 9.0% and 24.4%, respectively. The over-standard frequency of the daily average value of PM2.5 at the observation height of 454 m was 2.0%, and the over-standard amplitude was 10.4%. Accordingly, it can be stated that the air at the observation height 454 m above the ground did not reach the secondary limit of the new standards. The pollution was most serious during winter, and the air was relatively cleaner during summer. Overall, the vertical distributions of PM10, PM2.5, and PM1 decreased with height. The lapse rates showed the following sequence: PM10 > PM2.5 > PM1, which indicates that the vertical distribution of fine particles is more uniform than that of coarse particles; the vertical distribution in summer is more uniform than in other seasons.