Observation of particulate pollutants retained on Populus tomentosa and Pinus tabulaeformis leaves in urban environment.

This study aims to observe particulate pollutants retained on Populus tomentosa and Pinus tabulaeformis leaves in different environments of Beijing. Populus tomentosa. and Pinus tabulaeformis are representatives of broad-leaved and coniferous tree species, respectively. In this study, PM2.5 particles retained on the leaf surfaces of the two tree species at two sites were identified, counted, and analyzed by using an environmental scanning electron microscope (ESEM) and an X-ray energy dispersive spectrometer (EDS) in June and October, 2014. The results showed that PM2.5 is the main component of total particulate matters and these particles were mostly retained on the adaxial surfaces of Populus tomentosa leaves and the flat surfaces of Pinus tabulaeformis leaves. More particles were intercepted by Pinus tabulaeformis than by Populus tomentosa in per unit of leaf area. The number of PM2.5 from Xizhimen samples was more than that from Olympic Forest Park samples, and more particles were retained on leaves in October than in June. The components of PM2.5 at Xizhimen mainly contained aluminosilicate particles, soot aggregates particles and fly ash particles. The sulfur content of PM2.5 from Xizhimen samples was higher than that from the Forest Park samples. The stomata of Xizhimen leaf samples are smaller but more than those of Olympic Forest park samples.