| In recent years,the emergence of underground garages has become the main way to solve the parking problem due to factors such as the continuous increase in the number of cars and the reduction of available urban land resources.However,the underground garage is in a closed or semi-closed state,which makes it difficult for pollutants to diffuse and leads to excessive air pollution,which has great health risks to human.In order to explore the pollution characteristics of gaseous pollutants in underground garages,this study conducted field tests of CO and VOCs in a hotel underground garage in Xi’an from September 2020 to January 2021.In this study,the temporal and spatial distribution characteristics of gaseous pollutants and the variation characteristics of influencing factors(vehicle flow,temperature and relative humidity)were analyzed,and the influence of influencing factors on the concentration of pollutants was discussed.The main conclusions are as follows:(1)In the underground garage,vehicles mainly enter from 8:00am to 9:00am,while vehicles mainly leave from 12:00am to 13:00am.Both weekdays and rest days,traffic peaks between 12:00 and 14:00 and 17:00 to 19:00.The traffic flow was the highest in September,which was 141±14 vehicles per day.The lowest was 113±22 cars/day in November;In October,December and January,there was little difference in traffic.And the traffic flow on rest days was higher than that on weekdays.(2)The temperature in the underground garage is always higher than the outdoor temperature,and the temperature inside the garage is relatively stable,always higher than 0℃;In the underground garage,temperature level in autumn is more evenly distributed,and in winter the average temperature of the entrance and exit is lower than the inside of the garage;Humidity decreases sequentially from September to January,and the relative humidity in the innermost part of the garage is higher than the entrance and exit and the center of the garage.(3)Both CO and VOCs pollutants in underground garages have certain vertical distribution characteristics:the pollutant concentration is the lowest at 0.3 m,while the concentration difference between 1.5 m and 2.0 m is not big,and the overall bottom is low and the top is high;There are also differences in the level distribution of CO and VOCs in different months:in September and October,the pollutant concentration of the garage entrance and exit<the most mile of the garage<the center of the garage,while from November to January it is the entrance and exit of the garage<the center of the garage<the most mile of the garage.(4)The concentration of CO and VOCs in the underground garage reached the maximum in September,8.05±2.17 mg/m~3 and 8.16±2.46 mg/m~3,respectively.The lowest values in November were 2.61±1.09 mg/m~3 and 2.21±1.26 mg/m~3,respectively.Moreover,CO and VOCs have obvious seasonal differences.The concentration of CO and VOCs in underground garage on weekdays is lower than that on rest days;The change trend of VOCs concentration in the day and night is different,because the main influencing factors have changed.(5)In the underground garage,CO and VOCs concentration showed a significant positive correlation(p<0.01),and there is a situation in the underground garage where CO does not exceed the standard while VOCs exceed the standard.Therefore,VOCs should also be used as one of the pollution indicators of the underground garage.In the underground garage,the vehicle emission source was larger in September and January.The concentration of CO and VOCs was significantly correlated with the number of vehicles in the garage(p<0.05),but not with the number of vehicles in the garage(p>0.05).Generally,the concentration of pollutants was positively correlated with the number of vehicles per hour.In addition,the temperature and humidity in the underground garage can affect the emission of pollutants.The results of Pearson correlation analysis and partial correlation analysis show that there is a strong interaction between temperature and humidity in the garage,that is,the emission of pollutants will increase with the decrease of temperature,but decrease with the decrease of humidity.(6)Combined with the field test of underground garage,natural ventilation can not meet the ventilation requirements of underground garage,so the control of pollutants in underground garages should be combined with mechanical ventilation on the basis of natural ventilation,and vents should be arranged at reasonable positions,to ensure the air quality of underground garage. |
PDF Full Text Request