Nitrogen oxides (NOx) and Sulphur dioxide (SO₂) are the primary atmospheric pollutants contributing to acid rain. In the atmosphere, these gases react with water vapor, oxygen, and other substances to form nitric acid (HNO₃) and sulphuric acid (H₂SO₄). These strong acids then dissolve in precipitation, such as rain, snow, or fog, leading to acid deposition.
Carbon monoxide (CO): This gas is a toxic air pollutant primarily resulting from incomplete combustion. However, it is not acidic and does not participate in the chemical reactions that form the strong acids responsible for acid rain.
Ozone (O₃): Tropospheric ozone is a secondary pollutant and a greenhouse gas, formed through photochemical reactions. While it is an important atmospheric constituent, it does not directly contribute to the formation of nitric acid or sulphuric acid, which are the main components of acid rain.