What is smog?
- Smog is air pollution that reduces visibility.
- It was first described over 5 decades ago as a mixture of smoke and fog, hence the name “smog”—but today it has a more specific definition and composition.
- Smog is made up of many chemicals including nitrogen oxides (NOx), sulphur dioxide (SOx), carbon monoxide (CO), and volatile organic compounds (VOCs), but the two main components of smog are particulate matter (PM) and ground-level ozone (O3).
- PM stands for particulate matter (also called particle pollution): the term for a mixture of solid particles and liquid droplets found in the air.
Particle pollution includes:
- PM10 : inhalable particles, with diameters that are generally 10 micrometers and smaller; and
- PM2.5 : fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.
- Today, most of the smog we see is photochemical smog. Photochemical smog is produced when sunlight reacts with nitrogen oxides 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 these chemicals, they form airborne particles and ground-level ozone which appears as smog.
What is a smog tower?
- A smog tower is a structure with numerous layers of filters that catch tiny dust particles(particulate matter), which acts as a large-scale air purifier.
- The air is sucked into the tower via fans at the top, processed through filters, and finally discharged near the ground.
- Carbon nanofibres are a crucial component of the large-scale filters in these towers.
- A smog tower would lower 50% of the particulate matter load in an area of 1 kilometre in the wind’s direction, as well as 200 metres along the tower’s sides and against the wind’s direction.
- It may also lower particulate matter of 10 micrometres (PM10) by up to 45 percent in an open field in calm weather, and PM2.5 levels by up to 25 percent in a 20-meter radius surrounding the tower.
Why in News?
The Chief Minister of Delhi is set to inaugurate the city’s first “smog tower” to help purify polluted air.
Need for a smog tower in delhi
- The World Air Quality report by Swiss technology company IQAir has named Delhi as the world’s most polluted capital in 2021.
- During winter, pollution levels in Delhi rise considerably, reaching roughly ten times the WHO’s recommended levels. This is worrisome as the city’s sources of emissions — construction, industrial, and vehicular pollution are very constant.
- Smoke from stubble-burning in northwest states exacerbates the situation, which is exacerbated by unfavourable climatic circumstances such as calm breezes, cold temperatures, and fewer sunny days at the onset of winter.