The dust retention effect of urban vegetation in Huizhou, Guangdong Province

Abstract

Urban vegetation plays an important role in improving the urban atmospheric environment. The dust retention capacities of four urban tree species (Ficus virens var. sublanceolata (Miq.) Corner, Ficus microcarpa, Ficus altissima, Bauhinia blaheana) in Huizhou, Guangdong Province have been determined. The heavy metal and sulfur content of foliar dust in different urban areas are compared. Total urban vegetation biomass in Huizhou was calculated by analysis of remote sensing images, whilst the total leaf area of vegetation in Huizhou and the amount of dust retention by the urban vegetation over a year has been estimated. The results indicated that the amount of dust retention by the four tree species increased with time before the foliar dust amount reached their maximum. Dust retention capacities between F. altissima, F. virens var. sublanceolata (Miq.) Corne and F. microcarpa, B. blakeana. were significant different by 1.2-2.44 times (P< 0.05), following the trend of F. altissima > F. virens var. sublanceolata (Miq.) Corner > F. microcarpa > B. blakeana. Trees species dust retention ability is especially related to their leaf area, leaf inclination angle, branch hardness, the angle of branch extension and so forth. Cr, Cu, Zn, Cd, Pb, S contents in foliar dust and the amount of foliar dust for a given tree species in urban areas demonstrated remarkable differences between landuse (p<0.05), decreasing in the following order; the industrial area (IA), the commercial and transport infrastructure (CTA), the residential area (RA), and the control area (CA). There were extremely high loadings of heavy metals in the foliar dust in the urban areas, with the pollution index following the trend according to landuse: IA > CTA > RA > CA. The overall aboveground biomass of urban vegetation in the Huizhou built-up area was estimated to be 3.2×10 5 t, and its total leaf area, 808.4 km 2. The dust retention capacity was calculated at 4430.7 t per year. It could potentially remove approximately 1.63 t, 2.70 t,5.54 t, 0.04 t, 1.84 t, 19.52 t of Cr, Cu, Zn, Cd, Pb and S from the atmosphere, respectively.