Investigations On The Relationships Of Indoor And Outdoor Air Pollutant Concentrations During The Evolution Process

Ambient air pollution has received more and more attentions in many scientific fields with increasing in urbanization and industrialization in China. Traffic emission is believed as the main air pollution source in the urban environment in current days, and it is identified that outdoor air pollutants have many influences on indoor air quality (i.e., IAQ). Because most of the people spend 70%~90% of their time indoors in cities, the relationship between indoor and outdoor air quality should be investigated comprehensively, and practical models should be obtained for IAQ predicting and controlling.A series of experimental and theoretical investigations have been done on the relationships between indoor and outdoor pollutant concentrations in the present paper in Shanghai city and Xi'an city. Three rooms with natural ventilation and eleven streets (includes two streets which the viaducts crossed) are selected as sampling points, CO concentration and aerosol particle number concentration are employed as the test parameters for gaseous and particulate pollutants, respectively.The testing results show that street structure, local velocity of urban wind, traffic intensity and green plant pattern can affect the dispersion and the distributions of CO. By analyzing the models presented in literatures, OSPM and SRI model can be modified for the prediction of the variations of CO in street canyons. The so called K theory of atmospheric diffusion is used for discussing the vertical distribution of CO in street(includes the viaduct-crossed streets), and the results indicate the vertical concentration distribution of CO in both types of the street can be predicted as exponential functions of dimensionless height. The patterns of green-plants in cities is of more importance to urban air environment and landscape, but most of the models predicting the diffusion of traffic gaseous pollutants which be used currently do not consider the influences of the plant canopies. Gaseous pollutant distribution in typical streets in Xi'an city are monitored by employing CO as an environmental tracer in the present paper. The patterns of green areas and the diffusion of pollutants are also discussed by analyzing thetesting data, and some ideas for green ecological design in urban street is recommended.The evolution characteristics of outdoor and indoor CO concentration are compared and discussed in natural ventilating rooms. Considering mass balance of pollutant materials, a theoretical formulation is derived for describing time variation of CO concentration in indoors by introducing mixing factor and decay rate. The result confirmed that the decay effect of gaseous pollutants should be take into account for calculating CO concentration in ventilating rooms, and if no source exists in such rooms, indoor CO concentration will be the same as in outdoor with a relatively long time ventilation cause.Indoor to outdoor ratio (i.e., I/O ratio) of particle number concentration are found in the range from 0.276( 0.126) to 0.952( 0.198) in natural ventilating rooms in Xi'an city, I/O ratio will reduce with the increase of particle size. There is no time delay in the variation of particle concentration from outdoor to indoor, and a fine linear relation can be determined between I/O concentrations. When particle loss in room be considered, a formula can be obtained for predicting indoor particle numbers of different sizes, and the values calculated agree well with the tested data.