Diffusion And Influence Factors Research On PM_2.5 Of Automotive Exhaust In Transport Microenvironments

Automobile exhaust particulate matters increased pollution of the urban environment, causing more and more management attention. Studies have shown that PM_2.5 are the main causes of urban haze weather. The rapid growth of car ownership in the city, so that automobile exhaust PM_2.5 become a major source of urban air pollutants in the environment. Different automobile exhaust PM_2.5 and other atmospheric PM_2.5 emission sources is that its diffusion by mouth to an exhaust pipe near the ground and then to the atmosphere, automobile exhaust PM_2.5 distribution of diffusion characteristics research and influencing factors for the evaluation of traffic pollution situation microenvironment and the degree of influence of atmospheric pollution can provide technical basis.Analysis of PM_2.5 sources and chemical properties, based on the actual air quality data, the formation mechanism of secondary particles and the main gaseous pollutants correlation study showed a strong correlation automobile exhaust is the main city of PM_2.5 source. For PM_2.5 concentration diffusion, the effects of weather conditions, emission intensity and other factors.Testing the concentration dates of gasoline vehicles emission PM_2.5 in the rear of exhaust port which axial direction and the radial direction of longitudinal plane in a fixed environment. Research on characteristics which diffusion of the concentration of PM_2.5 in the rear of exhaust pipe. Under the influence of flowing rate which exhaust of the test vehicle, the concentration of PM_2.5 which the lower area of the exhaust pipe was significantly higher than other regions, the concentration of PM_2.5 which changes between 10-190μg/m3. Overall trends:first rising, then decreased until finally stabilized the background concentration.The actual observed the concentration of PM_2.5, the traffic flow, geometry of the street, meteorological factors and other dates. Research on concentration of PM_2.5 diffusion distribution and the dependency status of influence factors in the larger traffic flow. Based on a large number of test data, analyzed the diffusion of PM_2.5 which mobile automobile exhaust from the road to the pedestrian area of activity is concentrated. From the quantitative point of view, apply the SPSS software to analysis the test data of all factors by using the multiple linear regression. Analysis on the impact of various factors on diffusion of pollutants. Wind speed, emission intensity of PM_2.5 and the geometry of blocks play decisive roles in the diffusion of PM_2.5. In the most concentrated area of residents, the geometry of blocks which impact on diffusion of PM_2.5 is the most intense.Using LM algorithm improves the standard BP neural network, the measured data as training samples of neural network and prediction model based on the concentration of PM_2.5 LMBP Neural Network. As the traffic microenvironment concentration of PM_2.5 are short-term forecasting, high real-time requirement of the predicted results. LMBP neural network can achieve fast training and accurately predicted, it can meet the short-term and real-time online prediction.