The Establishment Of China’s Vehicle Emission Inventory Based On Urban Traffic Characteristics

With the acceleration of urbanization and the increasing improvement of people’s living standards,the rapid increase in the number of vehicles has become the cause of the "urban disease" of the current traffic congestion.It is also one of the important sources of the current atmospheric compound pollution.Guided by the goal of joint prevention and control of regional particulate matter and ozone,accurate quantification of vehicle air pollution emission inventories has become one of the key means to refine urban air pollution control.China’s vast territory spans nearly 50 degrees from south to north,thus the regional economic development is extremely uneven.Meanwhile,the traffic characteristics among cities are also obviously different.These make it difficult to accurately quantify China’s vehicle emission inventory.In view of this,through analyzing the environment,road traffic and motorcade information of 338 cities in China,this study uses sensitivity analysis to identify the key factors that affect vehicle emissions;uses K-means cluster analysis to identify the distribution characteristics of key factors in each city,and proposes a Chinese city classification system based on urban traffic characteristics;uses the motor vehicle emission factor model COPERT 5 to build an emission factor database based on the city classification system;then establishes the vehicle emission inventory and at last,the uncertainties and quality of the inventory are evaluated.The main conclusions are as follows:(1)Temperature,vehicle speed,accumulated mileage and vehicle emission standards are the main influencing factors of vehicle emissions.Based on these four main emission influencing factors,338 prefecture-level cities in China show 63 types of urban traffic characteristics classification.(2)For cities with different traffic characteristics,the CO emission factors of the same vehicle type have the largest difference,while other pollutant emission factors have relatively small differences.Taking the National III emission standard petrol passenger car as an example,for cities that belong to different urban traffic classification systems,the difference of CO emission factors can be up to 476%,which of VOCs emission factors can be up to 224%,and the NOx emission factors 144%.(3)The vehicle emission inventory established from the classification of urban traffic characteristics shows that in 2017,the emissions of SO2,CO,NOx,VOCs,PM10,PM2.5,NH3 and CH4 in China were respectively 10.22 Gg,9315.75 Gg,5365.33 Gg,1410.95 Gg,325.85 Gg,226.03 Gg,140.38 Gg and 172.49 Gg.(4)China’s vehicle emission structure shows the aggregation of vehicle type and geographical space.In terms of vehicle type,passenger cars and motorcycles are the main contributors to CO,VOCs and CH4 emissions,and heavy trucks are the main contributors to NOx,PM10 and PM2.5 emissions.In terms of geographical space,it has a central city agglomeration effect.The three city clusters around Bohai Sea,the Yangtze River Delta,and the Pearl River Delta are the major contributing regions.(5)Based on the characteristics of urban traffic,China’s vehicle emission inventory established in this study has a good comparability with other studies in terms of the total amount of emissions.At the same time,it can identify the emission characteristics of vehicles at the city scale in a more precise way,and provide ideas for the establishment of vehicle emission inventory with methodology and basic parameter selection.Also,it can reduce the uncertainty of vehicle emission inventory at the national scale.