The characteristics of particulate matter during an air pollution process revealed by joint observation of multiple equipments

Abstract

During a particle pollution in Hefei, Anhui Province from November 25 to December 9, 2018, we used a set of particle monitoring devices with different principles installed on the top floor of a 5-story experimental building to observe the mass concentration, particle diameter distribution and chemical composition. The results show that this pollution process can be divided into three stages: accumulation, outbreak and dissipation. At the beginning of pollution outbreak, it can be observed through the lidar that particulate matter first appears in the upper part of the boundary layer, and then accumulates downward and develops into ground pollution. During the pollution outbreak, particulate matter with an equivalent diameter of 0.8–1.6 μm increases significantly, with an average increase of more than 50%. In the particle size spectrum, the full width at half maximum also increases, and the particle diameter at the peak is about 0.76 μm. Furthermore, the change in particle size over time shows that the number concentration of particles with smaller size grows before those with larger size. By identifying and comparing characteristic ions, we found that the increase in the number of sulfate particles and the increase of their size correspond well to the outbreak of pollution, and the rapid decline in the fraction of sulfate corresponds well to the dissipation of pollution too. Sulfate is the most sensitive factor in the pollution process. The EC is the main component throughout the pollution process, but EC responds more slowly to pollution changes than sulfate, it is important but less sensitive.