Spatial-Temporal Variability and Dust-Capture Capability of 8 Plants in Urban China

摘要

Urban plants have been proven to mitigate ambient particulate matter (PM), which can benefit urban planners in their attempts to control urban air pollution. In this study, PM depositions on the leaves of 8 tree species were quantitatively analysed in 7 functional areas of the city of Nanjing, China, over the course of one year. The results demonstrated that leaf PM included different particle size fractions (PM 10 and PM2.5), and differed among seasons and species. The highest amounts of total PM, PM 10, and PM2.5 were found in the industrial area, and the mean values were 80.24 mu g/cm(2), 52.14 mu g/cm(2), and 15.51 mu g/cm(2), respectively, and the highest accumulation of total PM (60.65 mu g/cm(2)), PM10 (37.29 mu g/cm(2)), and PM2.5 (11.23 mu g/cm(2)) occurred in winter. Significant differences were found between the tree species tested. Cedrus deodara exhibited high amounts of the total PM, PM10, and PM2.5 accumulations. This study examined the mass and quantity distribution of PM among tree species, and identified the particles combined with a scanning electron microscope (SEM). In terms of particle mass, 48% of the identified particles had a diameter of 10 mu m, and only 18.3% of them had a diameter of 2.5 mu m. In terms of particle number, the results indicated that 73% of them had a diameter of 2.5 mu m, and only 5.5% of them had a diameter of 10 mu m. To test the relationship between leaf traits and PM2.5 accumulation, results showed that stomata size, density, and hair were significantly related to the PM2.5 capture quantity. As far as we know, this is the first paper to present the mass and quantity distribution of the PM of different tree species in Nanjing. The results not only give comprehensive insights into the dust-retaining capability of tree species but also offer a selection of species for urban green areas where the goal is to mitigate urban airborne PM.