Measurement Of Pollutant Emission From Urban Public Transportation System And Health Effects Of Health Risk Exposure Assessment

With the rapid progress of urbanization in China,the population of cities and towns is increasing,and the total demand for travel is increasing rapidly.In order to meet the travel needs of urban residents and relieve traffic pressure,governments at all levels have put forward relevant policies and measures of"giving priority to the development of public transport".Although these measures effectively promote the development of urban public transport industry and alleviate the pressure of urban passenger transport to a certain extent,due to the characteristics of large passenger volume,long operating mileage and frequent acceleration and deceleration of public transport vehicles in China,a large amount of exhaust gas has been produced in the whole public transport system,which has a serious impact on the urban atmospheric environment and the health of residents.Therefore,it is necessary to further study the pollutants in public transport.Based on the calculation of public transport pollution emissions,the main influencing factors of pollution emissions are analyzed,and the health risks caused by pollution emissions to urban residents are explored.On this basis,the relevant policy recommendations for public transport emission reduction and sustainable development are put forward.According to the research objectives,firstly,through the comparative analysis of the domestic and foreign scholars'calculation methods of vehicle pollutant emissions,the driving mileage method is selected to quantify the pollutants emitted by public transport.At the same time,in order to analyze the change mechanism of public transport pollution emissions,the related theory and modeling steps of system dynamics are introduced,and the scenario analysis of pollutants discharged by public transport is carried out by using this method.In order to further explore the impact of public transport pollution emissions on the health of urban residents,the exposure dose model and standard deviation index are introduced to explore the exposure dose and standard deviation index of pollutants.The variation of exposure dose in different population.By using the above methods,it is found that during the research period(2010-2017),CO accounted for the largest proportion of taxi pollution emissions,which was always around 50%,followed by NO_X,PM10 and PM2.5;and the most NOX emission from bus pollution was followed by CO,PM2.5 and PM10,and the emission of NO_X showed an upward trend,while the emission of the other three pollutants showed a downward trend and then an upward trend.Scenario analysis shows that CO emissions from public transport will show a steady downward trend in the next decade;NOx emissions will be more stable in the low-speed development scenario,declining slightly in the stable development scenario,and the fastest in the high-speed development scenario;PM2.5 and PM10 emissions change in the same trend,with the increase of development speed,the decline rate of PM2.5 and PM10 emissions is also increasing.The impact of CO,NOx,PM2.5and PM10 from public transport on young and middle-aged people is the greatest,followed by that on middle-aged and middle-aged students.The exposure doses of four pollutants vary greatly among different groups of people,and these differences change smoothly between2010 and 2017.Since then,the health risk exposure differences among the three groups have been decreasing.Based on the analysis of the results of the study and calculation,this paper puts forward relevant suggestions on public transport pollution reduction from four aspects:government level,traffic operation,practitioners and the general public.