地下车库的污染物扩散英文文献和中文翻译
Since many of the big cities experience a general lack of suffi-cient parking spaces, an increasing number of new office and residential build-ings is provided with underground parking garages to solve the permanentparking problems. In small building units, a natural ventilation of the parkingarea is often preferred to other solutions for economical reasons. Several build-ing codes have been developed in Germany in order to ensure a safe air qualityin parking spaces as well as to avoid health risks in closed parking areas. Car-bon monoxide (CO) was chosen as leading pollutant for the assessment of airquality in underground garages because it can be measured easily. Besides, areliable and permanent CO-monitoring can be used for controlling mechanicalemergency ventilation systems in situations that are critical with respect to airquality and pollutant concentrations. However, newer studies give evidence that there is a possibility of reaching or even exceeding the threshold values for othercritical air pollutants inside and outside of the parking area though the CO-basedair quality demands are satisfied inside a naturally ventilated parking garage.Benzene (C6H6) represents another air pollutant critical to human health, whichis used for assessing the impact of the exhaust from underground parking ga-rages on air quality outside the parking area. Benzene was selected as secondleading component for two reasons. First, benzene was found to be a carcino-genic air pollutant, which requires low threshold values and a special assessmentof exposure time to avoid risks for human health. Secondly, benzene is perma-nently emitted from underground garages. Driving vehicles release benzene asone component of the vehicles exhaust. Significant amounts of benzene are alsoreleased by parking vehicles because of evaporation of fuel and the effect of‘tank breathing’. In a recent study (TÜV Nord, 1996), maximum sourcestrengths of up to 75 µg/s benzene per ventilation outlet of underground garageswith natural ventilation were estimated. In a similar study by BAUCH (1993),average concentrations of 9.5 µg/m³ benzene with peak concentrations up to 18.1µg/m³ and a 90th-perzentile of 15 µg/m³ were measured in the exhaust gas of anunderground parking area. Considering typical mean background concentrationsof 5 to 7 µg/m³ benzene in large cities and a threshold value of 10 µg/m³ ben-zene defined in Germany, it becomes evident that even small amounts of ben-zene emitted by naturally ventilated parking garages can cause exceedances ofthe threshold value given by environmental guidelines.In order to study the flow and pollutant concentrations patterns close to theair outlets of naturally ventilated underground parking garages, a set of illustra-tive wind tunnel experiments has been set up in the BLASIUS wind tunnel of theMeteorological Institute at Hamburg University. The primary goal was to visu-alize critical emission situations near simplified building structures as well as onbuilding surfaces. In addition, it was intended to provide a set of high qualityexperimental data, which can be used for testing the quality of numerical model-ling, applied to a particular urban-type dispersion problem.2.