Q.Prepare a short table listing four major primary air pollutants. For each one, give its single dominant source and one significant health or environmental effect.

SO2 is a major air pollutant because it directly irritates lungs/plants and, once oxidised, forms acid rain, which damages ecosystems, crops and stone buildings.

Sulfur dioxide (SO2) is released mainly from the combustion of sulfur-containing fossil fuels (coal, diesel) in power plants, vehicles, and industries (e.g. smelting of sulfide ores). It is considered an air pollutant for several reasons:

1. Direct toxicity: SO2 irritates the mucous membranes of the respiratory tract, causing coughing, bronchitis, and worsening asthma; at high concentrations it can damage lung tissue.
2. Acid rain formation: SO2 dissolves in atmospheric moisture to form sulfurous acid, and is further oxidised (often catalysed by dust or ozone) to sulfur trioxide, which forms sulfuric acid: $SO_2 + H_2O \rightarrow H_2SO_3$ $2SO_2 + O_2 \rightarrow 2SO_3 \qquad SO_3 + H_2O \rightarrow H_2SO_4$ This acidified rain lowers the pH of soil and water bodies, harming aquatic life and vegetation. …