Plant canopies: bio-monitor and trap for re-suspended dust particulates contaminated with heavy metals

Urban and peri-urban vegetation is being considered for air pollution abatement. Appropriate plants with efficiency to adsorb and absorb air-pollutants are the prerequisite for green space development. The contributions of surface morphology towards plant’s ability to function as dust particulate adsorber and distribution of trace elements over the leaves are investigated in the present study. Dust interception efficiency was estimated for two roadside plant species named Ficus benghalensis, and Polyalthia longifolia. Leaves of both the plants are capable of capturing dust in the range of 0.12 mg/cm² to 1.89 mg/cm² on either of the leaf surfaces. However, variation in dust capturing capacity between the plants was observed. Leaf surface characters such as roughness, length, frequency of trichomes and frequency of stomata played a significant role in capturing re-suspended dust. Frequency (2 to 4 per 0.0004 cm²) and length (152.5 to 92.1 cm) of trichome showed negative co-relation trend, where as frequency and size of stomata showed positive co-relation trend. Elemental analysis by Scanning Electron Microscope attached with Energy Dispersive X-Ray Spectrometer (SEMEDS) indicated the presence of elements such as Sodium (Na), Magnesium (Mg), Aluminium (Al), Silicon (Si), Chlorine (Cl), Pottasium (K), Calcium (Ca), Iron (Fe), Zinc (Zn) and Arsenic (As). The results support the fact that plant canopies can be used for mitigation and bio-monitoring of air pollution as well.