Investigation On The Characteristics Of Air Pollution In Typaical Indoor And Outdoor Environment

People spend most of their time in built-environment in modern society. Study on the transportation characteristics of air pollutants in and out buildings has special significance for controlling and improving indoor or outdoor air quality. Therefore, some important problems about air pollution features in outdoor typical street canyons, relationships of pollutants between indoor and outdoor building environment, and pollutants dispersion characteristics in typical enclosure spaces are investigated and analyzed systemetically by employing numerical simulation and field measurement.The field measurement data shows that tree planting along street canyons is as important as buildings on the block effect of air contaminants dispersion. Therefore, ratio of the height of restrictive objects (buildings or tree planting) to the distance of them to the center of motor vehicles driveways, ratio of height to distance (H/D), is introduced to denote the constraint effect of street canyon obstacles. The total effective ratio of height to distance (H/DT) of the local street canyon monitoring site is equal to the maximum among those of all the individual restrictive objects (Hi/Di). On the condition of calm wind, the higher the H/DT, the stronger the restriction effect of the objects to the disadvantage of air contaminants dispersion.The total air exchange rateηt and local air exchange rateη1 are introduced to evaluate the air exchange level of street canyons. The numerical simulation results show that air flow structure, velocity gradient distribution and air exchange level are tremendously changed by buildings layout. Especially, when the buildings are stagger arrangement, and there are more interspaces, larger interspaces width among upwind buildings, the local air exchange rateη1 of street canyon will be larger, which is good for the air exchange and pollutants dilution. Particles average deposition rate on each surface of street canyons is mainly associated with flow field, particle diameter and location of the surface. About distribution of particles deposition rate on surfaces of street canyons, the largest ones appear near the edges of buildings, and they decrease gradually from the edges to the center of surface. The remarkable gradient variation exists near the edges, while almost no gradient variation in the surface center.The field measurement data indicates that there is closely correlation between indoor and outdoor air contaminant concentrations, for the terrible obturation feature of rural building in the southwest of Shandong Province. The types of heating facilities, fuel type and habit of resident daily activity have great effects on the variations of pollutant concentrations indoor and outdoor. Fireworks during the Spring Festival can produce large number of particles and gaseous contaminants, and the consequent pollution level depend on their form and height of blowing up.The experiment data in climate chamber indicates that the correlation of particle concentration between indoor and outdoor of a building is greatly affected by ventilation type and particle size distribution. For example, particle concentration in a mechanical ventilation room is directly affected by the outdoor concentration. Indoor particle concentration of a natural ventilation room changes with a time delay comparing to outdoor concentration. The primarily efficient filter of air conditioning room has a little influence on the correlation of fine particle concentration between indoor and outdoor environment. The consistency of particle concentration curves indoor and outdoor of a heating room is the worst among which mentioned above.Displacement ventilation (DV) room is one of the typical enclosure spaces. The numerical simulation indicates that the aerosol source location, temperature and vertical location of the inlet supply air have strong impact on the spatial distribution and removal rate of indoor particles. When the aerosol source location is low, there will be the satisfying vertical concentration stratification. The temperature and vertical location of inlet supply air do not greatly affect the air distribution in the upper part of a DV room, but could significantly influence the airflow pattern in the lower zone of the room.Rail transit system is another typical enclosure space. The monitoring information of representative stations of Shanghai Rail Transit System shows that air pollutant concentrations outside the stations are related to local traffic environment and layout features of buildings around stations. CO2 concentration inside stations is connected with density of passenger flow, background concentration and ventilation system. However, CO and particle concentration inside stations are not associated with density of passenger flow, but with sources inside and outside stations as well as their ventilation system. Specially, the underground spaces of stations, halls of Shanghai Railway Station and South Station of line 3, are polluted seriously, and there could be CO sources in all probability. The variations of monitored parameters of air quality in carriages of Shanghai Rail Transit System differ from their kinds, traveling direct, weekends and workdays. The correlation level between the monitored parameters and density of passenger flow from the strongest to the weakest is CO2, temperature and humidity in proper sequence. However, particle concentration in carriages primarily depends on the background concentration, and influence the density of passenger flow is relativily weak. In addition, the monitored parameters in carriages on line 9 vary at different extent when the train travels from the over ground elevated road to subterranean tunnel. Under the condition of the same density of passenger flow, CO2 concentration in carriages of line 3 is about 3.6 times higher than that of line 9.