Research Of Relationship Between Indoor/Outdoor PM2.5 And Its Heavy Metal Elements Contents Of Residential Apartments

In the recent years, the haze has become a frequent air pollution phenomenon in China. Atmospheric PM2.5 pollution is very serious. Ambient PM2.5 can enter into the indoor environment by ventilation and infiltration of buildings. People spend more than 80%of their time indoors, so the indoor PM2.5 exposure is more dangerous to occupant health. Therefore, it is very necessary to explore the indoor air PM2.5 concentration level and its chemical compositions, which is important for the protection of indoor air quality and understanding the impact of particle pollution on occupant health.In the paper, field experiments were conducted in three residential apartments with different HVAC-filter systems in Nanjing which located in the hot summer and cold winter area. HI with centralized air conditioning system, H2 with independent air conditioner and household heating system, H3 without HVAC-filter system. In the winter and summer from 2014 to 2015, the indoor and outdoor daily average mass concentrations of Total Suspended Particles (TSP) at different size bins(PM2.5, PM205～5, PM5～10, PM10～100)were sampled and instantaneously indoor and outdoor PM2.5 concentrations were monitored in three residential apartments and the immediately outside of the buildings simultaneously. Indoor and outdoor particulate size bins distribution, PM2.5 temporal and spatial distribution, and the correlation between indoor/outdoor PM2.5 concentrations were explored. In addition,9 heavy metal elements including Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Pb in PM2.5 were analysed. Based on this, main sources of PM2.5 were explored by EF and PMF model.The research found that PM2.5 was the primary particulate pollutant with obvious contents of heavy metal elements in indoor and outdoor environment of tested residential apartments in Nanjing. The indoor and outdoor PM2.5 concentrations in winter were higher than that in summer. Meanwhile, indoor air PM2.5 concentrations in all tested apartments were obviously lower than that of outdoors.The results revealed that indoor and outdoor PM2.5 concentrations had obvious correlation(P<0.05). The highest indoor PM2.5 concentrations and heavy metal elements contents appeared in H3 which was without any HVAC-filter systems.The indoor and outdoor PM2.5 correlation in H3 was the highest as well which indicated the impact of outdoor air pollution on indoor environment in H3 was significant. The lowest indoor PM2.5 concentration and heavy metal elements contents appeared in H1 which was conditioned by centralized HVAC-filter systems. The influence of outdoor particles pollution on indoor PM2.5 in H1 was the lowest. PM2.5 source apportionment showed that the main pollution sources of indoor and outdoor PM2.5 in Nanjing were metallurgical chemical dust, soil/surface dust, coal, vehicle exhaust and refuse incineration.