Acid rain causes extensive damage to buildings and structural materials of marbles. This attack on marble is termed as stone leprosy.
CaCO₃ + H₂SO₄ ⟶ CaSO₄ + H₂O +CO₂↑

The heating up of earth through the greenhouse effect is called global warming. Although the greenhouse effect is a naturally occurring phenomenon, it is intensified by the continuous emission of greenhouse gases into the atmosphere. During the past 100 years, the amount of carbon dioxide in the atmosphere increased by roughly 30 percent and the amount of methane more than doubled. If these trends continue, the average global temperature will increase which can lead to melting of polar ice caps and flooding of low lying areas. This will increase incidence of infectious diseases like dengue, malaria, etc

Thus Greenhouse effect may be denned as the heating up of the earth surface due to trapping of infrared radiations reflected by earth's surface by CO₂ layer in the atmosphere.

When ultraviolet radiations reach dioxygen molecule: in stratosphere, two free oxygen atoms are produced. II These oxygen atoms combine with dioxygen I molecule and forms ozone
\(O_{2(g)}\xrightarrow{UV}O_{}(g)+O_{(g)}\)
\(O_{(g)}+O_{2(g)}\overset{UV}\leftrightharpoons O_{3(g)}\)

Since the photochemical smog is formed as a result of photochemical reaction between oxides of nitrogen: and hydrocarbon, hence it is name so.