Characteristics Of Atmospheric Particle Number Concentration And Size Distribution In Indoor Environment In Jinan

An observation was conducted in five typical indoor environments during spring and winter2010in Jinan, which is one of the most polluted populous areas in China. In this paper, we presented the characteristics of particle number concentration and size distribution, in order to show the aerosol pollution feature in indoor environment.In all sites, particle numbers were distributed in Aitken mode (20-100nm), accounting for approximately60%of the total. The level of particle number concentration was comparable to the developed countries, while the mass concentration was about an order of magnitude higher, which is due to the different size distribution of particle number concentration. In all sites, the particle surface concentration was distributed in accumulation mode (100-1000nm), accounting for more than85%. The total particle surface concentration in winter was significantly higher than the spring, indicating the worse indoor air quality in winter. In all sites, the particle volume concentration was distributed in accumulation mode, with higher percentage in winter than spring. In winter, under the condition of high outdoor pollution level on accumulation particles, the volume concentration distributed much less in the coarse mode (more than1000nm), indicating that the indoor mechanical activities such as walking or cleaning had a small contribution. In spring, the outdoor pollution level on accumulation mode particles was relatively lower, so the contribution of indoor human mechanical activities was bigger. In the classroom, the use of chalks can produce particles in coarse mode, resulting in the comparable volume distribution in accumulation mode and coarse mode.The diurnal variations of different size-bin particles as well as the related gaseous pollutants showed quite different patterns in different sites, because their indoor particle source and outdoor environment were different. There was no significant indoor particle source in the dining hall, and the nucleation particle reached its peak value at noon, while the Aitken mode particles had two obvious traffic-hour-peaks at about8:00and18:00. Similarly, the indoor air quality was mostly controlled by the outdoor’s in the commercial office. The nucleation mode particle had a peak at noon, and there were two traffic-hour-peaks, however, the occasional tobacco smoking made the20-200nm particles continue to elevate at10:00to11:00, after the traffic rush hours. The cooking activity made the particle sources in the dining hall much more complex. Besides the peak value of nucleation mode particles at noon, and the traffic-hour peaks in the morning and afternoon, there were also three cooking-peaks for both nucleation mode and Aitken mode particles in about7:00,12:00and18:00. The nucleation mode particles in the classroom reached its peak value at noon, and there was only one traffic-hour-peak because of the change of the outbound traffic during the weekends and Tomb-sweeping Day. The diurnal variation pattern in the office was quite special, with an all day long high level of Aitken mode particles because of the extreme outdoor weather condition, and there was neither peak hour at noon for nucleation mode particles, nor the traffic-hour-peak for Aitken mode particles.Different indoor particles sources were observed, and their contribution to the indoor air quality was analysed. The walking and cleaning the shopping mall made the volume concentration of coarse mode particles rise to5-7times higher, however, its contribution to the total volume concentration was limited. The printer use in the commercial office could emit a huge number of20nm particles and thus had a serious risk to human health; tobacco smoking could greatly change the size distribution of indoor particle number and volume concentration, and had a serious impact on the indoor air quality for hours.A particle growth event was observed with a3.4nm h"1growth rate, which is comparable to previous studies. During a long stretch of non-haze days with low relative humidity and high wind speed, a continuously high level of ultrafine particles was observed, and traffic exhaust played an adverse role in the total number concentration under this special condition.