[摘要] Aerosol number size distributions have been measured since 5 May 1997 inHelsinki, Finland. The presented aerosol data represents size distributionswithin the particle diameter size range 8-400nm during the period fromMay 1997 to March 2003. The daily, monthly and annual patterns of theaerosol particle number concentrations were investigated. The temporalvariation of the particle number concentration showed close correlationswith traffic activities. The highest total number concentrations wereobserved during workdays; especially on Fridays, and the lowestconcentrations occurred during weekends; especially Sundays. Seasonally, thehighest total number concentrations were observed during winter and springand lower concentrations were observed during June and July. More than80% of the number size distributions had three modes: nucleation mode(
30nm), Aitken mode (20-100nm) and accumulation mode(
90nm). Less than 20% of the number size distributions hadeither two modes or consisted of more than three modes. Two differentmeasurement sites were used; in the first (Siltavuori, 5.5.1997-5.3.2001),the arithmetic means of the particle number concentrations were 7000cm
,6500cm
, and 1000cm
respectively for nucleation,Aitken, and accumulation modes. In the second site (Kumpula,6.3.2001-28.2.2003) they were 5500cm
, 4000cm
, and 1000cm
.The total number concentration in nucleation and Aitken modeswere usually significantly higher during workdays than during weekends. Thetemporal variations in the accumulation mode were less pronounced. The lowerconcentrations at Kumpula were mainly due to building construction and alsothe slight overall decreasing trend during these years. During the sitechanging a period of simultaneous measurements over two weeks were performedshowing nice correlation at both sites.
