Aerosol Dynamics in an Urban Area Observed by Multipoint Measurement

Abstract

Air pollutant concentration in an urban area is determined by the reaction-diffusion system, which is usually non-linear. Thus, the concentration often shows complicated tempo-spatial variations. Although such variations were first recognized in the 1980's, there have been few observations since then because of technical insufficiency for the measurement. However, recent development of technology has enabled us to measure the air pollutant concentration which complicatedly varies in time and space.
In this study, we adapted a dust sensor for the field measurement. The sensor was originally designed as a built-in device in an air cleaner, and it had sufficiently high time resolution and was compact and inexpensive enough to conduct multipoint measurements of aerosol concentration. The tempo-spatial variations of aerosol concentration were measured at a heavily polluted intersection in Kawasaki City. The observed concentration distributions showed complex patterns being significantly different from those predicted based on a simple decay depending on the distance from the sources. We also proposed a method for correcting the interinstrumental discrepancy, which is a source of serious error in multipoint observations. In addition, some information was obtained on chemical composition of the aerosol particles.