In Focus: Smog @UpscExpress

In Focus: Smog

  • Very simply, smogis a type of air pollution that reduces visibility.
  • The term “smog” was first used in the early 1900s to describe a mix of smoke and fog, when smoke came from burning of fossil fuels like coal in thermal power plants.

Sulphurous Smog

  • It is also called “London smog”.
  • It results from a high concentration of sulphur oxidesin the air and is caused by the use of sulphur-bearing fossil fuels, particularly coal.
  • This type of smog is aggravated by dampness and a high concentration of suspended particulate matter in the air.

Photochemical Smog

  • Another type of smog is photochemical smog.
  • Photochemical smog is produced when sunlight reacts with nitrogen oxides (NOX) and at least one volatile organic compound (VOC) in the atmosphere.
  • Nitrogen oxides come from car exhaust, coal power plants, and factory emissions.
  • VOCs are released from gasoline, paints, and many cleaning solvents.
  • When sunlight hits VOCs and NOX, they form a combination of airborne particles and ground-level ozone which is called as smog.
  • Impact of Photochemical Smog:
    • The photochemical smog causes a light brownish coloration of the atmosphere, reduced visibility, plantdamage, irritation of the eyes, and respiratory distress. 
    • Ozone in the lower levels of troposphere can damage lung tissue, and it is especially dangerous to people with respiratory illnesses like asthma.
    • It can also cause itchy, burning eyes.
    • Smog is unhealthy to humans and animals, and it can kill plants.
    • It makes the sky brown or gray and reduces visibility.

In Focus: Smog Towers

  • A smog tower is a structure designed to work as a large-scale air purifier.
  • Smog towers are fitted with multiple layers of filters which trap fine dust particles suspended in the air as it passes through them.
  • Air is drawn through fans installed at the top of the tower, passed through filters, and then released near the ground.

Examples of Smog Towers:

  • Smog towers have been experimented with in recent years in cities of Netherlands, China, South Korea and Poland.
  • First Smog Tower of World
    • The first such tower was erected in 2015, in Rotterdam, Netherlands, created by Dutch artist Daan Roosegaarde.
    • It is a 7 metre-high ‘smog free tower’ which can filter 30,000 cubic metres of air per hour around it.

  • Smog Towers of China
    • Beijing has a smog tower.
    • Smog tower of Xian- The University of Minnesota has helped design a 100-metre high permanent smog tower in the Chinese city of Xian. This tower was completed in 2017, and is said to be the world’s biggest air purifier.

  • Delhi’s Smog Tower at Lajpat Nagar
    • The first ‘smog tower’ was installed at Lajpat Nagar Central Market of Delhi
    • It became operational in January 2020.
    • This smog tower has a height of around 20 ft.
    • It is estimated to purify the air within a circumference area of almost 500 meters to 750 meters. The purifier aims at treating 2,50,000 to 6,00000 cubic meter air per day and release fresh air in return.

About: Delhi’s Pollution Problem

  • Delhi and its suburbs have ranked among the most polluted cities in the world frequently since 2014, when the WHO declared Delhi the most polluted city in the world.
  • Pollution levels in Delhi increase dramatically during winter- on some days to nearly 10 times above the limits prescribed by WHO, posing a serious risk to vulnerable and also healthy populations.
  • However, an assessment by the CPCB shows that Delhi’s air quality has been improving every year since 2016, even as it remains above acceptable limits, as a result of the pollution control measures being taken
  • Causes of Air Pollution in Delhi
    • Delhi’s air pollution is largely because sources of emissions from construction work, industrial and vehicular pollution in and around the city.
    • The situation is aggravated at the start of winter by smoke from stubble-burning in northwestern states, coupled with unfavourable meteorological conditions, such as calm winds, low temperatures, and fewer sunny days.

  • Measures Taken for Mitigating Air Pollution in Delhi
    • Persuading farmers in Punjab and Haryana to use mechanical alternatives to stubble-burning.
    • Closure of thermal power stations in Delhi.
    • Making industries use piped natural gas, in addition to control measures taken under the Graded Response Action Plan (GRAP) when pollution levels spike.

Effectiveness of Smog Towers

  • Experts have claimed that the smog towers in Delhi would create “clean air zones” in the city.
  • An estimate made of their impact on air quality shows a tower would reduce 50% of the particulate matter load in an area of 1 kilometre in the direction of the wind, as well as 200 metres each along the sides of the tower and against the direction of the wind.
  • Delhi’s Environment Department is of the view these smog towers may not be useful for the whole city, but they can be useful in creating ‘clean air area’ zones in different parts of the city.
  • Another expert panel set up by the Centre’s Department of Science and Technology had estimated that 213 smog towers may be required across the whole city of Delhi.

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