Studies on Atmospheric Purification as a Function of Buffer Planing Belts on Roadsides

Experiments on Trapping Particulates by Foliage

Abstract

Lately, particulate pollutants that are exhausted by motor vehicles have become an issue. The author made some experiments on trapping the particulates by foliage for explaining the atmospheric purification as a function of buffer planting belts on roadsides. The site of the experiments were near the eastern portal of Nihonzaka tunnel of Tomei-expressway, and ring road Route 7 and 8 in Tokyo. The results of this paper are summarized as follows:
The quantity of particulates trapped by foliage was related to property of the leaves. Small leaves with complicated structure such as serrations, veins and downs were better for increasing of the quantity.
As a result of long term experiments at Tomei-expressway, the quantity was related to the exposed term, and their regression equation was a linear one with a high correlation coefficient in spite of passable rainfall and wind during the term.
And the quantity was related linearly to a concentration of particulate pollutants in the air near the foliage. For that reason, it is necessary for increasing the quantity that the planting site is as near as possible to the source of the pollutants and the polluted air is positively induced into the foliage.
Based upon the results, the quantity of particulates trapped by the buffer planting belt that does not have dense foliage was estimated by computer. At normal atmospheric condition and for a normal arterial road with four lanes, the value obtained was approximately 20kg/year in case of the planting belt of 20m×500m (1ha).