How do sulfur dioxide emissions turn into sulfuric acid in the atmosphere?

In the atmosphere, sulfur dioxide ($S{O}_2$) emissions contribute to acid rain through a series of chemical reactions involving water and oxygen.12

The process generally follows these steps:

• Oxidation: Sulfur dioxide reacts with oxygen in the atmosphere to form sulfur trioxide ($S{O}_3$). This can be represented by the chemical equation: $2S{O}_2+O_2\to 2S{O}_3$.345
• Hydration: Once formed, sulfur trioxide reacts with atmospheric water vapor to produce sulfuric acid ($H_{2}S{O}_4$). The reaction is: $S{O}_3+H_{2}O\to H_{2}S{O}_4$.345

Alternatively, sulfur dioxide can dissolve directly in atmospheric water droplets to form sulfurous acid ($H_{2}S{O}_3$), which can further oxidize to become sulfuric acid. These resulting acids mix with cloud moisture and fall to the ground as precipitation, lowering the pH of the rain. This process is a significant environmental concern, as the resulting acidity can damage forests, aquatic ecosystems, and human-made structures.3416