Effects of different external factors on urban roadside plants for the reduction of airborne fine particulate matters.

With the progress of urbanization and industrialization in China, the consumption of fossil fuels blows up. The burning of fossil fuels releases large amounts of particulate matter, leads to smog, and the air quality is gradually getting worsen. Previous studies have shown that vegetation can effectively reduce airborne particles with different size fractions. And large amounts of previous studies pointed to the adsorption ability of urban forest for particles larger than 2.5 μm. The capacity of roadside plants for the capture of fine particles, especially for those smaller than 2.5 μm has been rarely reported. In this study, five external factors including leaf orientation, leaf height, planting location, planting form, and pollution concentration were tested to evaluate their impact on the dust retention capacity of different roadside plants. The results indicate that significant interspecies was found between tested plant species, and with the change of different external factors, the capturing capacity for the same roadside plants varied. The change of leaf orientation has limited effects on the amount of captured fine particles for the tested plants. While, the amount of captured particulate matter by leaves was inversely proportional to its growth height. Plants locating in the central of the road showed significantly higher capturing capacity than they, when they was set alongside the road. The total amount of captured fine particle by locating in the central green belt of road was about 5 times higher than it when it was planted in the green belt alongside the road. In addition, the correlation between the capturing capacity of roadside plants and its distance to the street curb was found to be negative.