The influence of exhaust gas from automobiles on ambient quality was investigated by measuring the variation of nitrogen oxides (NOx) concentrations around the arterial road. The NOx concentrations were measured continuously for two weeks in February 1999 in both sides of the two arterial roads in Kawasaki City, Kanagawa Prefecture. In order to obtain the spatial distribution of nitrogen dioxides (NO2) concentration, about 70 passive samplers of the molecular diffusion type were deployed on each of the 25m spaced grid points of the field experimental area. The NO concentration at the curbside was about 70ppb and decreased by about 30% at 25m from the road. The rate of concentration decrease was lower for NO2 than for NO. The NO2 concentration decreased by 10% at 25 m from the road. A statistical analysis was performed for the data obtained from the field experiment. This analysis has revealed that the variation of NOx concentrations with the perpendicular distance was significant. (A)
Abstract