A combination of bottom-up and top-down approaches for calculating of air emission for developing countries: a case of Ho Chi Minh City, Vietnam

A comprehensive emission inventory (EI) was conducted in Ho Chi Minh City (HCMC), the largest city of Vietnam rapid urbanization rate. In 2017, HCMC had 8.6 million inhabitants with a total of nine millions of private vehicles, 19 manufacturing and industrial zones, 30 industrial clusters, and numerous other factories and enterprises. All those sources could contribute to the high levels of emissions which caused the potentially negative impact on human health and environment. The aims of this study were (i) application bottom-up and top-down approaches to conduct a complete air emission inventory, (ii) development of spatial distribution of air emission, and (iii) estimation of emission forecast for HCMC by 2025 and 2030. A combination of bottom-up and top-down approaches was employed to conduct air pollution EI, in which EMISENS model was utilized to generate the EI for road traffic sources. The results showed that the motorcycles were the main reasons of emission in HCMC, contributing 90% of CO, 68% of non-methane volatile organic compounds (NMVOC), 63% of CH4, 41% of SO2, 29% of NOx, and 18% of patriculate matter (PM2.5). The emission forecasts for HCMC by 2025 and 2030 also were calculated based on the data of strategies and plans for socioeconomic development of HCMC. The results showed that the emissions of pollutants will increase around 30 to 50% by the year 2025 and from 40 to 65% by the year 2030. If the local government does not have any plan for the reduction of emissions (scenario of socioeconomic development as usual), the emissions will increase significantly.