Diurnal Variations of Tire Tread Concentration in Particulate Matter

Abstract

Department of Applied Chemistry, Faculty of Science and Technology, Keio University; Hiyoshi, Kohoku-ku, Yo kohama-shi 223 Japan The daily and weekly variations of the concentration of tire tread in the atmosphere were measured at the high density urban area in Shinjuku, Tokyo in summer and spring. The air samples were continuously collected through the monitoring periods with a 4-8 h sampling cycle to discuss the variations of the concentrations of tire tread in relation to a fundamental cycle of human activities. The concentration of tire tread in the urban air was clearly high in the day time compared to that in the night and higher weekdays than sunday. These tendencies are in accordance with a cycle of human activities or a cycle of daily life in the urban area. The concentration of tire tread in Hiyoshi, Yokohama located about 20 km from the center of Tokyo depends on the direction of the wind. Particularly, it was high when the wind came from the north-west and the north-east. The vertical distribution of tire tread in the atmosphere indicated that the particle sizes of tire tread are larger than those of suspended particulate matter other than rubber particles.