Portal de Periódicos da CAPES

Variation of concentration of ambient aerosols in Tokyo

1990; Elsevier BV; Volume: 24; Issue: 6 Linguagem: Inglês

10.1016/0960-1686(90)90047-q

1878-2124

Kazuhiko Miura, Toshio Sekikawa,

Air Quality Monitoring and Forecasting

The number concentration of aerosol particles dispersed in the urban atmosphere was measured at Kagurazaka in central Tokyo from January 1980 to December 1987. Aitken particle number concentrations were measured with a Pollak condensation nuclei counter and a diffusion battery. The characteristic radius was deduced, using the DeMarcus equation, from the measured concentrations. Mie particle number concentrations ranging from 0.055 to 2.5 μm in radius were measured with two optical particle counters. Slope and intercept of the Junge distribution were calculated for particles > 0.15 μm. The main results are as follows. (1) For these 8 yr, there are no long-term trends in the particle number concentrations, characteristic radius, and slope and intercept of the Junge distribution. (2) Aitken particle number concentrations show regular seasonal variations, with a maximum during winter and a minimum during summer. They also show regular diurnal variations, with an increase during daytime and a minimum in the early morning. Detailed discussions suggest that these variations are affected by anthropogenic sources and meteorological conditions. (3) Mie particle number concentrations show neither a clear seasonal nor diurnal variation. The variations are strongly dependent on meteorological conditions. Our careful analysis shows that wind speed is most important of the meteorological elements. Mie particle number concentrations decrease as wind speed increases, often by as much as two-thirds. This effect was observed for all wind directions.