Definition of Smog

A mixture of smoke and fog, caused by the burning of coal, vehicular emissions, and industrial fumes (primary pollutants).

Components of Smog

Soot particulates, smoke, sulfur dioxide (SO2), nitrogen dioxide (NO2), and other components.

Types of Smog

• Sulfurous Smog (London Smog)
• Photochemical Smog (Los Angeles Smog)

Primary Pollutants

Air pollutants directly emitted from a source, e.g., sulfur dioxide, nitrogen oxides, hydrocarbons.

Secondary Pollutants

Pollutants formed when primary pollutants react in the atmosphere, e.g., ozone, acid rain.

Formation of Secondary Pollutants

• Ozone: Formed when hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight.
• Acid Rain: Formed when sulfur dioxide (SO2) or nitrogen oxides (NOx) react with water.

Sulfurous Smog

• High concentration of sulfur oxides in the air, mainly from burning coal.
• Common in areas where coal is used as a primary fuel (e.g., London).
• Aggravated by dampness and suspended particulate matter.

Photochemical Smog

• Occurs in urban areas with high automobile emissions.
• Formed when nitrogen oxides (NOx) and organic compounds react with sunlight to form ozone.
•  Causes light brown coloration, reduced visibility, plant damage, eye irritation, and respiratory issues.

Chemical Reaction for Ozone Formation

Nitrogen Dioxide (NO2) + Sunlight + Hydrocarbons = Ozone (O3)

Impact of Ozone

Beneficial in the stratosphere but a greenhouse gas at ground level, contributing to global warming.

Haze

• An atmospheric phenomenon where dust, smoke, and dry particles obscure the sky.
• Similar to smog but without condensation.
• Sources include farming, traffic, industry, and wildfires.

Effects of Smog

• Toxic to humans, causing sickness, shortened life, or death.
• Reduces visibility and contributes to respiratory distress.
• Increases atmospheric pollution, especially during temperature inversion.
• Reduces precipitation and accentuates temperature inversions.

Temperature Inversion

Traps pollution close to the ground, exacerbating the effects of smog in cities like LosAngeles, Beijing, Delhi, and Mexico City.

Carcinogenic Components

Ozone (O3), Carbon monoxide (CO), and Sulfur dioxide (SO2) are carcinogens present in smog.

PRACTICE QUESTION

Q.Smog has emerged as a significant environmental and health challenge in urban areas. Discuss smog's causes and effects on the environment and human health. What measures can be taken to mitigate its impactin rapidly growing urban centers?(250 words)