ISSN: 2717-4417

Document Type : Research Paper


1 Assistant Professor, Department of Physical Geography, Faculty of Geography, University of Tehran

2 M.A. graduated of Climatology, Department of Physical Geography, Faculty of Geography,, University of Tehran

3 Assistant Professor in University of Tehran

4 Assistant Professor Department of Physical Geography, Faculty of Geography, University of Tehran



Today, urban development and air pollution are the most important issues concerning urban climate that can affect the quality of urban life. Despite the significant progress made in the fuel and engine technology, emission of pollutants in urban environments is still prevalent. As in many other countries, the environmental issue is particularly evident in the large cities of Iran such as Tehran, Tabriz, Isfahan, Shiraz, Arak, and Karaj. The rapid urbanization, industrialization, and increasing trend in the use of motor vehicles have caused numerous environmental issues, including the production and distribution of different types of air pollutant, especially in Tehran, the capital. Tehran’s confinement by mountains and meteorological factors such as temperature inversion, the persistence of high-pressure systems with cold air, and local winds exacerbate pollution. Hence, numerous studies have been conducted on air pollution in Tehran. The results have indicated that 73% to 85.5% of the air pollution observed at urban stations is caused by temperature inversions, which are influenced by high pressure and surface radiation. According to the above research, the key factors involved in the spread of pollution over the streets besides the spatial and natural factors that can affect the distribution of air pollutants (i.e. geographic location, topography, etc.) include the arrangement of the buildings, particularly in terms of street width and orientation, distance, and intersections. It should be noted given the significance of the issue that the pollution can have extensive effects although it occurs at the street level, due to the interaction of the dispersal and diffusion of pollutants through meteorological conditions (wind speed and direction and atmospheric stability), the configuration of buildings, and the orientation of streets. Therefore, the main purpose of this research was to specify the characteristics of pollutant flow and dispersion on urban passages in micro scale. For that purpose, the meteorological data, including air temperature, relative humidity, and wind speed and direction, were extracted from Iran Meteorological Organization (IMO) Geophysics Weather Station (the closest station to the area under investigation) for a 20-year statistical period (1991-2010). Two areas (1 and 2) in Municipal District 6 were specified as making up the area under study in this research. Then, the pollutant dispersion data were obtained based on the relationship between traffic volume and pollutant production during two winter and summer months (July and January) and at three times of the day (morning, midday, and afternoon). Finally, the distribution of air pollutants was simulated using the ENVI-met microscale model for building configuration and street orientation in the area under investigation. The results demonstrated that street and pathway orientation plays an important role in the accumulation or distribution of pollutants. Accordingly, the density of pollutants is higher in streets that are perpendicular to the prevailing wind direction. Furthermore, the concentration of pollutants in the main streets of the area under study exhibited a significant relationship with their directions. Pollutant concentration was moderate in streets with prevailing north winds, while the highest and lowest amounts of pollutant concentration were observed in streets with south and southwest winds, respectively. It can be concluded that consideration of the climate conditions in urban design and development (wind speed/direction in particular) can be effective in improvement of air quality in urban areas.

Air Pollution, Street Orientation, Wind Speed/Direction, Tehran, ENVI-met Model.


Main Subjects

Ali Akbari Bedokhti, A. and Z. Shariipour (2009). "Upper Air Meteorological Conditions and Air Pollution Conditions (Case Study: Tehran)." Environmental Studies 52: 1-14 [In Persian].
Asadi, M. (2009). "Explaining the role of public transport in a sustainable urban environment." M.Sc. Thesis, Faculty of Environmental Science, University of Tehran. [In Persian].
Boddy, J., R. Smalley, N. Dixon, J. Tate and A. Tomlin (2005). "The spatial variability in concentrations of a traffic-related pollutant in two street canyons in York, UK—Part I: the influence of background winds." Atmospheric Environment 39(17): 3147-3161.
Deljoo, A. (1999). "Investigation of temperature inversion and instability on Tehran." M.Sc. Thesis, Islamic Azad University. [In Persian].
Di Sabatino, S., R. Buccolieri, B. Pulvirenti and R. Britter (2008). "Flow and pollutant dispersion in street canyons using FLUENT and ADMS-Urban." Environmental Modeling & Assessment 13(3): 369-381.
EnsafiMoghaddam, T. (1993). "Investigation of Tehran air pollution and its relationship with temperature inversion." M.Sc. Thesis, Faculty of Human Sciences, Tarbiat Modarres University. [In Persian].
Eskani Kazazi, A. and M. Lale Siah Pirani (2010). "Synoptic analysis of Tehran air pollution." Journal of Geography No.2: 135-161 [In Persian].
Faraji, A. (1999). "Weather and Climatology." Carno Publications, Tehran [In Persian].
Fenger, J. (1999). "Urban air quality." Atmospheric environment 33(29): 4877-4900.
Hunter, L., G. Johnson and I. Watson (1992). "An investigation of three-dimensional characteristics of flow regimes within the urban canyon." Atmospheric Environment. Part B. Urban Atmosphere 26(4): 425-432.
Karra, S., L. Malki-Epshtein and M. K.-A. Neophytou (2017). "Air flow and pollution in a real, heterogeneous urban street canyon: A field and laboratory study." Atmospheric Environment 165: 370-384.
Kastner-Klein, P. and E. Plate (1999). "Wind-tunnel study of concentration fields in street canyons." Atmospheric Environment 33(24-25): 3973-3979.
KianMehr, A. and H. Bahraini (2016). "Investigation of the Effect of Direction and Wind Speed on Ventilation and Contaminants in Street Corridors." Environmental Science 14: 97-108 [In Persian].
Landsberg, H. E. (1981). The urban climate, Academic press.
Lateb, M., R. N. Meroney, M. Yataghene, H. Fellouah, F. Saleh and M. Boufadel (2016). "On the use of numerical modelling for near-field pollutant dispersion in urban environments− A review." Environmental Pollution 208: 271-283.
MacNaughton, P., S. Melly, J. Vallarino, G. Adamkiewicz and J. D. Spengler (2014). "Impact of bicycle route type on exposure to traffic-related air pollution." Science of the total environment 490: 37-43.
Mohammadi, H. (2011). "Urban Meteorology." Tehran Press, University of Tehran. [In Persian].
Panjahkoubi, P. (2011). "Analysis of Relationship between Tehran Air Pollution and Temperature Inversion." M.Sc. Thesis, Faculty of Geography, University of Tehran. [In Persian].
Pourdyhimi, S. (2011). "Climate in Sustainable Environmental Design (Application of Climatology in Environmental Planning and Design), Volume I: Large and Medium Scale." Shahid Beheshti University Press, Tehran. [In Persian].
Qasami, T., A. Ali Akbari Bedokhti, A. Sedaghatkerdar and F. Sahraian (2007). "Investigation of Synoptic Conditions in Several Critical Periods of Tehran Air Pollution." Environmental Science and Technology 9: 229-238 [In Persian].
Ranjbar Saadatabadi, A., A. Ali Akbari Bedokhti and S. Sadeghi Hosseini (2003). "Case Study of Thermal Island and its Numerical Simulation." Journal of Earth and Space Physics 31(No.1): 63-78. [In Persian].
Ranjbar Saadatabadi, A., Mohammadin Mohammadi, L. (2010). "A Study of Mean Synoptic Patterns Based on Occurrence of Different Concentrations of CO in Summer and Autumn Seasons in Tehran." Natural Geography Research(No.72): 111-127 [In Persian].
Safavi, Y. and B. Alijani (2006). "Study of Geographical Factors in Tehran Air Pollution." Geographical Researches(No.58): 99-112 [In Persian].
Saidnia, A. (1989). "Location of Tehran City." Journal of Environmental Studies(No.15): 1-10 [In Persian].
Shamsipour, A., A. (2012). "Climate Modeling; Theory and Method." University of Tehran Publications, First Edition, 2012. [In Persian].
Shamsipour, A. and J. Amini (2013). "Simulation of CO Distribution Pattern with Envi-Met Micro-Climatic Model on the Azadi-Tehranpars." Geography and Environmental Hazards(No.7): 85-103 [In Persian].
Shamsipour, A., A. Ashrafi, M. Alikhah Asl and K. Ashrafi (2015). "Modeling Particle Distribution Pattern in the South of Tehran (Case Study: Tehran Cement Factory) with AERMOD Model." Environmental Studies(No.4): 799-814 [In Persian].
Shamsipour, A., F. Najibzadeh and Z. Hosseinpour (2013). "Simulation of the Distribution Pattern of Tehran Meskaetropolitan Air Pollution in Windy Days." Geography and Environmental Hazards(No.4): 19-36 [In Persian].
Sharifi, M. (2009). "Investigation of air pollution caused by passenger terminal in the surrounding urban context." M.Sc. thesis, Faculty of Environment, University of Tehran. [In Persian].
Sini, J.-F., S. Anquetin and P. G. Mestayer (1996). "Pollutant dispersion and thermal effects in urban street canyons." Atmospheric environment 30(15): 2659-2677.
Tehran, C. o. S. a. P. o. (2013). "Investigating the Impact of Forms  of City on Air Quality (Tehran Case Study)."  Report No.22, Deputy of Studies and Planning of Infrastructure and Master Plan.
Vardoulakis, S., B. E. Fisher, K. Pericleous and N. Gonzalez-Flesca (2003). "Modelling air quality in street canyons: a review." Atmospheric environment 37(2): 155-182.
Wong, P. P., P.-C. Lai, R. Allen, W. Cheng, M. Lee, A. Tsui, R. Tang, T.-Q. Thach, L. Tian and M. Brauer (2019). "Vertical monitoring of traffic-related air pollution (TRAP) in urban street canyons of Hong Kong." Science of the total environment 670: 696-703.
Xie, S., Y. Zhang, L. Qi and X. Tang (2003). "Spatial distribution of traffic-related pollutant concentrations in street canyons." Atmospheric Environment 37(23): 3213-3224.
Yuan, C., E. Ng and L. K. Norford (2014). "Improving air quality in high-density cities by understanding the relationship between air pollutant dispersion and urban morphologies." Building and Environment 71: 245-258.