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A few days ago .I received a call from my sister in Tehran. It was night time in Tehran, so by using her camera she showed me a few lights on a camp on the mountains of northern Tehran that I used to go most weekends. Mountain climbing is a weekend habit of many people in Iran.
She called me again yesterday and said that she was surprised that she was not able to see those lights any more. Also, she said that the temperature has dropped and the city is very cold.
So I did a literature review of the current problem of the pollution in Tehran and found out that the problem is much worse than what I thought. Climate change and government's poor regulation has done its job.
Tehran, the capital of Iran, is located in the north of the country with a population of about 8.5 million. The population can reach over 12.5 million during the day, with people from nearby cities commuting daily to Tehran for work. There are more than 17 million vehicular trips per day in Tehran, and many of the vehicles have outdated technology. Thus, the air in Tehran is amongst the most polluted in the world. Topography and climate add to the pollution problem. Tehran is at a high altitude and is surrounded by the Alborz Mountain Range, which traps polluted air. Temperature inversion, a phenomenon particularly occurring during the winter months, prevents the pollutants from being diluted. Several recent trends indicate that reducing air pollution will not be straight forward: rapid population growth (partially due to migration from other cities), industrial development, urbanization, and increasing fuel consumption are pressure points for clean air in Tehran. To design an effective approach to air pollution management, it is important to diagnose the problem, determine its sources, and identify affordable and sustainable solutions.
Tehran with higher levels of sulfur dioxide than India and Bangladesh. In the 50s, 60s and 70s, along with a rapid population growth of Tehran, automobile ownership raised dramatically. Establishment of Iranian car production factories like Iran Khodro and Pars Khodro, and also foreign car import caused massive inflow of cars into the streets of Tehran.
On the other hand, many industrial factories were established in the same period of time around Tehran, especially in south, south west, and west of the city. Cars and factories have a major role in the dangerous pollution in Tehran. However, some other factors like land-use planning, urban form and weak public transit encourage residents to use personal automobiles. In addition to the mentioned factors, the geographical characteristics of the location of Tehran make the air pollution problem of the city harder to solve.
The studies show how geographical specifications of Tehran like direction of wind, rainfall, inversion, topography, and so on, affect the quality of air. Among these factors, it seems that the wind direction and topography, which work together, have the most influential role in the in the air pollution of Tehran . A BBC report (in Persian) says that 27 people a day die in Tehran from air pollution-related diseases. The north of the city is blocked by Alborz Mountain and the eastern and south eastern parts of the city are captured by some shorter heights like Bibi Shahrbanoo Mount in the south-east.
The dominant wind of Tehran blows from west to east. And most of the industries of Tehran are placed in west and south west. So the wind brings the pollutants to the city and there is no escape way through the eastern heights. In the meantime, if there were a way out in the eastern mounts, the western winds could clean a part of the emissions of the automobiles.
Shortage of rainfall of Tehran is another factor that could have reduced the pollution. In Tehran, in every 3 days of fall and winter, there is a probability of a rainfall greater than 5 mm. It is believed that rainfall of more than 5mm is effective in washing the air. The rain is less important in cleaning the air in comparison with wind, because the rain washes the air pollutions to the soil. But the wind directs the pollutant to the outer limits of the city.
The number of inversion and smog days of Tehran seems to increase every year and this is an alarming sign for the city and governmental authorities. Some strategies have been implemented but the number of dangerous or polluted days have not dropped during the recent years.
Information collected from the Green Prophet.
(Article changed on Nov 04, 2021 at 4:51 AM EDT)
(Article changed on Nov 04, 2021 at 4:53 AM EDT)
(Article changed on Nov 04, 2021 at 12:19 PM EDT)