Profiling the PM_2.5 mass concentration vertical distribution in the boundary layer

Abstract. Fine particles (PM_2.5) affect human life and activities directly; the detection of PM_2.5 mass concentration profile is very essential due to its practical and scientific significance (such as the quantification of air quality and its variability as well as the assessment of improving air quality forecast). But so far, it has been difficult to detect PM_2.5 mass concentration profile. The proposed methodology to study the relationship between aerosol extinction coefficient and PM_2.5 mass concentration is described, which indicates that the PM_2.5 mass concentration profile could be retrieved by combining a charge-coupled device (CCD) side-scatter lidar with a PM_2.5 sampling detector. When the relative humidity is less than 70 %, PM_2.5, mass concentration is proportional to the aerosol extinction coefficient, and then the specific coefficient can be calculated. Through this specific coefficient, aerosol extinction profile is converted to PM_2.5 mass concentration profile. Three cases of clean night (on 21 September 2014), pollutant night (on 17 March 2014), and heavy pollutant night (on 13 February 2015) are studied. The characteristics of PM_2.5 mass concentration profile at the near-ground level during the cases of these 3 nights in the western suburb of Hefei city were discussed. The PM_2.5 air pollutant concentration is comparatively large close to the surface and varies with time and altitude. The experiment results show that the CCD side-scatter lidar combined with a PM_2.5 detector is an effective and new method to explore pollutant mass concentration profile at the near-ground level.