An emission inventory update for Tehran: The difference between air pollution and greenhouse gas source contributions

摘要

Many highly populated cities are still struggling to reach clean air targets, while the zero greenhouse gas emission objectives may accelerate the path toward healthy air for all. Still, there is a fine line between intensive electrification's impact on greenhouse gas emissions and criteria air contaminants depending on the source of the electricity. In this study, the previous version of the emission inventory for Tehran was evaluated and recalculated in a detailed bottom-up approach to provide the most updated data on the contribution of stationary sources derived by power plants vs. mobile sources. The objectives were to update the emission inventory for improved policymaking, study the impact of changes in emissions in 4 years, provide a detailed methodology for cities highly impacted by transportation emissions, and exercise a simple yet effective modelling task for emission inventory evaluation. The study included all possible sources in the mobile sector with eight categories of fleet composition, industries, power plants, house heating, and point sources related to transportation such as terminals and gas stations. It also included exhaust, non-exhaust, and evaporative emissions for mobile sources. An intensive data collection campaign was launched to collect activity data. The traffic information was obtained from a travel-demand model and validated by traffic counting. The license plate registration database provided detailed fleet composition based on vehicle technology, fuel, age, and state of maintenance. The emission inventory calculated annual emissions of 478 kt for CO, 103 kt for NOx, 91 kt for VOCs, and 19 kt for SOx. TSP was estimated at 10.4 kt. NOx emissions were significantly increased from 87 to 102.6 ktonnes per year (17 increase) and were confirmed by an increase in the annual mean concentration of NO2 from 39.4 to 53.4 ppb (35 increase) between 2013 and 2017. A notable observation was the impact of house heating on CO2,eq emissions. More than 30 of CO2,eq emissions were from house heating (natural gas, predominantly methane) in a city where total air contaminant emissions are highly driven by the transportation sector. The result clearly shows the differences between zero-emission target paths for the two objectives of greenhouse gas emissions and air quality. An integrated approach is needed to develop policies that will lead o zero-emission GHG targets while keeping the air clean.