Question

Consider the relevance of the following features for causing photochemical smog:

1. Air stagnation.

2. Abundant sunlight

3. High concentration of NO_x in atmosphere.

4. High concentration of SO₂ in atmosphere.

Which of the above features are correct?
1. 1, 2 and 4 only
2. 3 and 4 only
3. 1, 2 and 3 only
4. 1, 2, 3 and 4

Answer 1

Correct Answer - Option 4 : 1, 2, 3 and 4

Smog is a mixture of smoke and fog.

The photochemical smog is caused by interaction of some hydrocarbons and oxidants like SO₂ or NO_x under the influence of sunlight giving rise to formation of dangerous peroxy-acetyl-nitrate (PAN).

The main constituents are: Nitrogen oxide, PAN, HCs, Ozone and CO. 

The atmospheric conditions favourable for formation of photochemical smog are:

1. Presence of high concentration of hydrocarbons and NO_x in atmospheres.

2.  Air stagnation i.e.  Air pollutants are not dispersing.

3. Abundant sunlight.

Effects of photochemical smog:

1. Eye irritation – caused by PAN.

2. Vegetation Damage- caused by  PAN, NO₂.

3. Visibility reduction

4.  Cracking of rubber