The Relative Contributions of Mobile Sources to Air Pollutant Emissions in Tehran, Iran: an Emission Inventory Approach

Abstract

Tehran, a city with 8.5 million inhabitants, has suffered from rapid and unplanned urbanization in recent years resulting in substantial environmental impacts perhaps foremost of which is poor air quality. A major source of air pollution is emissions from mobile vehicles; therefore, having an accurate and comprehensive mobile source emission inventory is essential for decision-makers to develop mitigating strategies. The aim of this study is to determine the relative contributions of specific mobile sources to key air pollutants through the development of an emissions inventory for mobile sources in the city of Tehran using the International Vehicle Emissions (IVE) model. Tehran traffic data were acquired to obtain link level emission rates, using IVE emission rates. The developed emission inventory was evaluated using Tehran gasoline sales data. The results indicate that the sources of carbon monoxide (CO), volatile organic compound (VOC), nitrogen oxide (NO x ), and sulfur oxide (SO x ) emissions are mainly passenger cars. The contribution of emissions of CO, VOCs, and particulate matter (PM) from motorcycles to the total traffic emissions is more than 15, 31, and 12 %, respectively. Despite the fact that medium and heavy-duty vehicles (minibuses, buses, and trucks) only comprise 2.4 % of the Tehran fleet, they contribute more than 41, 64, and 85 % of the NO x , SO x , and PM emissions, respectively. Analyzing the distribution of the aggregated emission of pollutants shows that emissions are mostly higher in central zones due to the high traffic rate of passenger cars, taxis, motorcycles, and buses.

Temporal variations of ambient air pollutants and meteorological influences on their concentrations in Tehran during 2012–2017

“…Tehran as the capital and most populous city of Iran has faced intense ambient air pollution, particularly criteria air pollutants (PM 10 , PM 2.5 , O 3 , NO 2 , SO 2 and CO), in the last two decades due to unsustainable development of industrialization and urbanization, the ever-growing automotive fleet and their emissions alongside ineffective national ambient air quality standards and Middle Eastern dust storm [3][4][5][6] . In fact, ambient air pollution in Tehran has become one of the most challenging environmental issues for Iranian central government, authorities, policy-makers, Tehran citizens, national and international researchers 3,[7][8][9] . It is estimated that approximately 98% of CO, 75% of PM 2.5 and 46% of NO X are emitted from mobile sources in Tehran 4,10 , confirming the need for appropriate sustainable control policies and regulations against vehicular traffic, such as mandatory applying state-of-the-art technologies to reduce road traffic-related emissions, and more effective and serious implementation of transportation policies 4 .…”

“…Similar to other O 3 -precursors (NO X and CO) in Tehran, VOCs are mainly emitted from mobile sources (approximately 86%) 4,13 . To date, numerous investigations have been conducted in Tehran that have focused on various issues of ambient air pollution, including investigation of chemical characterization of ambient particulate matter 14,15 and their toxicological effects 16 , ambient particulate matter source apportionment 10 , health effects of ambient air pollutants 3,17 and emission inventory of ambient air pollutants 7 . Although remarkable investigations have been conducted, a comprehensive and in-depth understanding temporal variability of all criteria air pollutants as well as the meteorological influences on their concentrations using a robust method remains unclear in Tehran to date.…”

Sources and Temporal Variations of Coarse Particulate Matter (PM) in Central Tehran, Iran

“…Ambient PM sampling was performed at two residential sampling locations in central Tehran. [39,41,45]. Therefore, both of the sampling sites of this study are exposed to all of the abovementioned sources, as identified by our previous PM 2.5 source apportionment study [46,50] at the same sampling sites.…”

“…Therefore, both of the sampling sites of this study are exposed to all of the abovementioned sources, as identified by our previous PM 2.5 source apportionment study [46,50] at the same sampling sites. In addition, considering that the vast majority of the Tehran population lives in/near the city center [39], it can be argued that our sampling sites properly represent the population exposure to major sources of air pollution in the metropolitan area of Tehran. Figure 1 illustrates the map of the study area with the locations of our sampling sites.…”

“…Tehran, the capital of Iran with a population of nearly 9 million residents [36], has experienced several severe episodes of air pollution during the past few decades [37]. The large number of mobile sources (more than 4 million vehicles) in that megacity, as well as its proximity to a large number of industrial units have led to serious air pollution challenges in Tehran [38,39]. This situation is further exacerbated by the topography of the area, being surrounded by Alborz mountains to the north and east.…”