ABSTRACT
To avoid the spread of COVID-19, China has implemented strict lockdown policies and control measures, resulting in a dramatic decrease in air pollution and improved air quality. In this study, the air quality model WRF-Chem and the latest MEIC2019 and MEIC2020 anthropogenic emission inventories were used to simulate the air quality during the COVID-19 lockdown in 2020 and the same period in 2019. By designing different emission scenarios, this study explored the impact of the COVID-19 lockdown on the concentration of air pollutants emitted by different sectors (industrial sector and transportation sector) in Nanjing for the first time. The results indicate that influenced by the COVID-19 lockdown policies, compared with the same period in 2019, the concentrations of PM2.5, PM10, and NO2 in Nanjing decreased by 15%, 17.1%, and 20.3%, respectively, while the concentration of O3 increased by 45.1% in comparison;the concentrations of PM2.5, PM10 and NO2 emitted by industrial sector decreased by 30.7%, 30.8% and 14.0% respectively;the concentrations of PM2.5, PM10 and NO2 emitted by transportation sector decreased by 15.6%, 15.7% and 26.2% respectively. The COVID-19 lockdown has a greater impact on the concentrations of PM2.5 and PM10 emitted by the industrial sector, while the impact on air pollutants emitted by the transportation sector is more reflected in the concentration of NO2. This study provides some theoretical basis for the treatment of air pollutants in different departments in Nanjing.
ABSTRACT
Pollutants emitted from motor vehicles have become an important source of air pollution. Based on the traffic flow data of the expressways in Fujian Province, a high-resolution pollutant emission inventory of the expressways from January to July in 2020 was established by the bottom-up calculation method. The results show that under the influence of the COVID-19, the monthly average traffic flow and pollutant emissions of the expressways in Fujian province decreased firstly and then increased. Pollutant emissions reached the lowest in April, and quickly recovered to the pre-COVID-19 emission level in May. The pollutant emissions of the CO, HC, NOx, PM2.5 and PM10 in the middle stage of the COVID-19 decreased by 90.68%, 89.06%, 92.58%, 89.58% and 89.63%, respectively, compared with those in the post stage of the COVID-19. In the entire study period, different cities have different sharing rates of the pollutant emissions from motor vehicles, with Quanzhou, Fuzhou and Zhangzhou having higher motor vehicle emission sharing rates on the expressways. In terms of the vehicle types, the small passenger buses and the light trucks are the main contributors for CO and HC, and the heavy trucks and the light trucks are the main contributors for NOx and PM. In terms of the fuel types, the gasoline vehicle is the main source of CO and HC, and the diesel vehicle is the main source of NOx and PM. In terms of the emission standards, vehicles with China 3 and China 4 have the largest contribution rate to various pollutants. However, the spatial distribution of various pollutants is consistent, with the higher level emissions in the eastern coastal expressways, while the lower level emissions in the western inland expressways. From the spatial distribution of NOx emission intensity of Expressways in Fujian Province, the emission intensity of each section in March and April was at a very low level. Taking the main emission of the motor vehicle: NOx as a case, the Shenyang-Haikou Expressway section has the highest NOx emission intensity. Moreover, the Xiamen and Quanzhou sections of Shenyang-Haikou Expressway have relatively high exposure levels of motor vehicle pollution, while other sections have relatively low exposure levels. © 2022, Science Press. All right reserved.