Emission characteristics and high-resolution spatial and temporal distribution of pollutants from motor vehicles in Chengdu, China

Abstract

The establishment of the air pollutant emission inventory of urban motor vehicles is the key to control motor vehicle pollution; therefore, the purpose of this paper is to develop an air pollutant emission inventory of urban motor vehicles in Chengdu. The IVE model localization including the actual measurement correction was completed, the motor vehicle emission factors on various types of roads in Chengdu's different development areas were calculated, and the 1 km × 1 km on-road mobile source emission inventory for the year of 2016 was established in the bottom-up method based on the collected data on road network, traffic flow, vehicle driving cycle, the vehicle population in Chengdu, etc. The inventory showed that the CO, VOCs, NOx, SO2, PM10 and NH3 emissions of Chengdu's on-road mobile sources had reached 432.2 kt, 44.8 kt, 72.4 kt, 0.4 kt, 11.3 kt and 6.2 kt respectively in 2016. Light-duty vehicle, medium-duty vehicle, and heavy-duty vehicle were the major contributors to CO emissions, and their CO emissions accounted for 44%, 14% and 11% of the total CO emission respectively; VOCs mainly came from light-duty vehicle, motorcycle, and heavy-duty truck, the VOCs emissions of which accounted for 49%, 19% and 10% of the total VOCs emission respectively; NOx and SO2 mainly came from light-duty vehicle and heavy-duty truck, the NOx emissions of which accounted for 25% and 48% of the total NOx emission, and the SO2 emissions of which accounted for 70% and 14% of the total SO2 emission respectively; in addition, the heavy-duty truck caused PM10 emission accounting for 78% of the total PM10 emission, while the light-duty vehicle caused NH3 emission accounting for 81% of the total NH3 emission. The spatial distribution of on-road mobile source pollutant emissions showed that emissions were concentrated in the downtown with a decreasing trend from the downtown to the suburbs and the outer suburbs. Based on the 95% confidence intervals, the uncertainties of CO, VOCs and NOx emission estimations were relatively low with relative errors ranging from - 68% to 87%, 58%–84% and 97%–75%. Considering the uncertainties of the traffic flows and emission factors, the on-road mobile source emission inventory shall be further improved to provide important scientific research supporting for the prevention and control of air pollution in Chengdu.