Anti-smog guns

In news: Vehicle-mounted ‘anti-smog guns’ have begun their rounds in Delhi as air quality begins to take a turn for the worse.

• A Supreme Court order from 2020 mandated the use of anti-smog guns at large construction sites, road construction stretches and dust-prone traffic corridors.
• While only large construction sites of 20,000 sqm or more needed them last year, they have now been mandated by the Delhi government at smaller construction sites of 5,000 sqm or more.

About:

• In winter, conditions are dry and with repeated action on the top soil, dust gets lifted and is unable to settle due to low humidity.
• Anti-smog guns spray water in a fine mist to get suspended dust and particulate matter to settle.
• It uses water’s ability to remove pollutants called as wet scavenging.
• It is useful especially in emergency situations, where there is a fire or construction and demolition dust.
• CPCB’s guidelines on anti-smog guns: Water throw distance ranges from 30 metres to 100 metres depending on the device.

• Anti-smog guns can also be rotated.
• Treated waste water is not to be used in the anti-smog gun.

Concerns:

• There has been no thorough scientific analysis so far to determine what impact they have, and there could be some brief effect at best.
• Humidification may make the particles bigger and can lead to larger drops.
• It is not a permanent solution since water itself is an important resource. The guns use 40 to 250 litres of water per minute depending on the device.

Source: Indian Express

Previous Year Question

Q.1) Photochemical smog is a resultant of the reaction among (2013)

1. NO2, O3 and peroxyacetyl nitrate in the presence of sunlight
2. CO, O2 and peroxyacetyl nitrate in the presence of sunlight
3. CO, CO2 and NO2 at low temperature
4. High concentration of NO2, O3 and CO in the evening