Characteristics of air pollution distribution in naturally ventilated underground parking garages in Xi'an city
Objective To understand the spatial and temporal distribution characteristics of particulate matter(PM),total volatile organic compounds(TVOC)and benzene,toluene,xylene(BTX)concentrations in the typical underground parking garages(UPGs).Methods Natural ventilation UPGs in Xian city were monitored in four seasons,and the relationship between PM,TVOC and BTX concentrations in UPGs and internal and external environmental factors was statistically analyzed.Results UPGs'PM pollution was severe in winter,with higher concentrations at the exit.TVOC and BTX pollution was severe in summer,with higher concentrations at the core of the traffic.The diurnal variation of pollutants indicated that concentrations were higher in the afternoon and evening.There was a significant relationship between pollutant concentrations and exit vehicle flow(P＜0.01).Conclusion Seasonal variations of PM2.5 and PM10 concentrations in UPGs are mainly influenced by outdoor particulate matter concentrations,and the indoor physical environment is an important factor in generating seasonal variations of BTX.Traffic activities are the main source of BTX.Daily variations of indoor pollutant concentrations are mainly dependent on traffic volumes.The correlation between BTX and TVOC suggested that internal motor vehicle activity emissions may be a major source of pollutants from UPGs.
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