Quantifying the particulate matter accumulation on leaf surfaces of urban plants in Beijing, China

Abstract

Particulate matter is potentially harmful to human health but green tree species act as air filters to adhere these particulates. The elemental composition, number density, and size fractions of particles on leaf surfaces of 14 urban green from Xizhimen overpass and the Olympic Forest Park in Beijing, China were examined by scanning electron microscopy and X-ray energy dispersive spectrometry. Particles that accumulated on leaves were comprised mainly of C, O, Si, Ca, Fe, and Pb. The number density of particles was 50,961.5 mm−2, and 52.9% and 25% of the particles were submicron (<1 μm) and fine (<2.5 μm), respectively. The densities and size fractions of the particles deposited on the adaxial and abaxial side of leaves were significantly different, and 24% of the particles were deposited on the abaxial side of leaves. The densities of the particles in four size fractions differed significantly among the species at the two sampling sites. Salix matsudana, Euonymus japonicus, Magnolia denudate, Sophora japonica, Amygdalus persica, and Salix babylonica efficiently captured all particle sizes on their leaf surfaces. S. matsudana, E. japonicus, M. denudate, S. japonica, Fraxinus chinensis, and Ginkgo biloba efficiently captured submicron and fine particles, which can have serious effects on human health. These differences among species provide more insight into the sink capacity of green tree species, and the efficiencies of plant species for trapping particulates can be used to guide urban tree planning and decrease air pollution.