Abstract
This paper presents daytime vertical profiles of the NOx concentration, and the number concentration and size distribution of fine particles near a major road in urban Tokyo during spring 2011. No significant height dependence was observed in the NOx concentration, presumably due to rapid diffusion. In contrast, the number concentration of particles under 0.5 µm diameter demonstrated an exponential decrease with increasing height above ground level. Vertical profiles derived from this study differ from those presented in previous studies, however, these differences may potentially be explained by the different tailpipe positions of Japanese and US heavy vehicles, as well as the meteorological conditions. This study demonstrates that in Tokyo, the fine particle concentration at 0.5 m above ground level was about 2.9 times higher than that at 2.0 m. The higher fine particle concentration immediately above ground level implies that children may be at greater risk of experiencing pollutant-related respiratory symptoms than adults.
Highlights
Exhaust from heavy vehicles contributes one of the major anthropogenic source of the gaseous pollutants CO, NOx and NMHCs, as well as fine particles
Several epidemiological studies into respiratory symptoms caused by inhaling anthropogenic fine particles have demonstrated that the prevalence of asthma may be related to regional motor vehicle traffic density and residential proximity to freeways (Holguin 2008; Patel and Miller 2009; Salam et al, 2008), while other studies reported that there was no evidence to suggest such a relationship (Waldron et al, 1995; Livingstone et al, 1996)
This study focuses on determining the vertical profiles of the NOx concentration and number concentration of fine particles within a busy urban street in central Tokyo
Summary
Exhaust from heavy vehicles contributes one of the major anthropogenic source of the gaseous pollutants CO, NOx and NMHCs, as well as fine particles. Several epidemiological studies into respiratory symptoms caused by inhaling anthropogenic fine particles have demonstrated that the prevalence of asthma may be related to regional motor vehicle traffic density and residential proximity to freeways The vertical distribution of particles does not indicate exponential decay with increasing distance from the emission source, the maximum concentration typically occurs close to ground level (
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