The Effects of Atmospheric Pollutants

Sulfur dioxide

When fuels containing sulfur are burned, the sulfur atoms are oxidised. They react with oxygen in the air to form sulfur dioxide gas:

Sulfur + Oxygen → Sulfur dioxide

S + O2 → SO2

In the atmosphere, sulfur dioxide can undergo further oxidation to form sulfur trioxide gas. This gas dissolves in rainwater to form acid rain, producing sulfuric acid (H2SO4). The process involves two reactions:

1. Sulfur dioxide + Oxygen → Sulfur trioxide

2SO2 + O2 → 2SO3

2. Sulfur trioxide + Water → Sulfuric acid

SO3 + H2O → H2SO4

Acid rain is a type of rain that has a high level of dissolved acidic compounds in it. There are many problems associated with acid rain, including:

  • Causing the pH of water bodies to drop, which can result in the death of fish and other aquatic life
  • Damaging buildings and statues
  • Polluting crops

Oxides of Nitrogen

Oxides of nitrogen are pollutants typically produced inside vehicle engines and then released. For example, the high temperatures in cars cause nitrogen to react with oxygen in the air to produce a range of molecules. We call these molecules oxides of nitrogen or NOx.

Nitrogen + Oxygen → Oxides of Nitrogen

N2 + O2 → NOx

NOx gases react with other pollutants in the atmosphere to form photochemical smog, which can affect the health of individuals, especially those suffering from asthma.

Both sulfur dioxide and oxides of nitrogen contribute to acid rain.

An illustration of the effects of acid rain. Dry deposition shows dust particles being deposited. These pollutants are transformed into acidic particles that harm plants. Meanwhile, water from the ocean is depicted evaporating and later condensing back as acidic rain.