Study On The Intensity And Diffusion Of Traffic Pollution Sources At Urban Road Intersections Under Low Temperature Conditions

With the rapid economic development and the continuous improvement of people’s living standards,people have put forward higher requirements for the environmental space in which they live.The increase in the motor vehicle population contributes to road environmental pollution.In order to effectively control road environmental pollution and improve people’s living environment.Because the low temperature condition of motor vehicle almost only occurs in winter in cold city,this paper analyzes the background of winter in cold regions.Aiming at the common problems of serious traffic congestion,high idle rate,concentrated and difficult diffusion of motor vehicle emissions in winter of cold regions,this paper studies the emission source model and line source model of urban road motor vehicle emissions,and conducts case analysis and model verification.Based on the analysis of the technical level and emission characteristics of motor vehicles,the emission characteristics of traffic pollution in winter of cold region are analyzed.This paper analyzes the influence of traffic characteristics,turbulence zone,obstacles on roadside and building volume on line source mode in winter of cold region.The influence of signal timing parameters and main evaluation indexes on the intensity of emission sources at urban road intersections is analyzed.In terms of the research on the line source mode of road traffic pollution,the paper based on the characteristics of atmospheric low frequency of wind speed and street valley aspect ratio in the cold region road,according to the relationship of the road width,road length,average speed,traffic volume,wind speed,wind direction and the diffusion parameters,the influence of headway of transverse longitudinal diffusion parameters is analyzed.According to its diffusion characteristics,the exhaust gas diffusion area is divided into primary diffusion area and mixing area,and its diffusion parameters are calibrated respectively.Introducing the turbulence diffusion correction term affected by headway into the original,in order to achieve the accuracy of using line source models to calculate the pollutant concentration and reverse source strength.In terms of the research on the emission source intensity model of urban road intersection,based on the analysis of applicability of strong emission source model of urban road traffic pollution source,this paper selects the CAL3 QHC model for improvement and comparison.According to the characteristics of severe traffic congestion,high idle rate,concentrated and difficult diffusion of motor vehicle emissions in winter of cold regions,this paper improves the driving state of motor vehicle assumed by the original model from idle state and free flow state to acceleration state,deceleration state,idle state and free flow state.Then the emission of four driving states are calibrated through the actual measurement of typical road intersections and bench experiments in cold cities,and the vehicle emission factors of idle state and free flow state are corrected by using the IVE model.The improved CAL3 QHC model is closer to the actual situation,which reduces the error of the model calculation and thus improves the accuracy of the emission source intensity model.the method of line source model amendment and the improvement measures of Urban Road intersection emission source intensity model proposed in this paper are of great significance for the accurate measurement of urban road pollutant emission intensity,and help to provide a more targeted management strategy basis for the traffic management department.According to the study of urban road traffic pollution in cold regions winter in China,this paper puts forward the correction method of line source and the improvement measures of urban road intersection emission source intensity model,which is of great significance to the accurate measurement of urban road pollutant emissions intensity has important significance and help to provide more targeted traffic management strategy for the traffic management department.