Question

Photochemical smog consists of

• A. $O_3,S{O}_2$ and hydrocarbons
• B. $O_3$, PAN and $N{O}_x$
• C. $S{O}_2,C{O}_2$ and hydrocarbons
• D. $S{O}_2$, PAN and smoke

Answer 1

Answer: (B)

$O_3$, PAN and $N{O}_x$

Photochemical smog is the result of sunlight induces chemical reaction between the primary pollutants to form the secondary pollutants. This produces an effect of smoke and fog. The primary pollutants like volatile organic compounds, hydrocarbons, oxides of nitrogen, oxides of sulphur react with water vapours and oxygen in the presence of sunlight to form the ozone, peroxyacetyl nitrate and nitrous oxides. These secondary pollutants persist in the environment and decrease the visibility other than causing the deficiency of oxygen. Their presence induces severe respiratory illness in humans and animals and also affect the physiology of plants.

Hence, the correct answer is 'O${}_3$, PAN and NO${}_x$'.