4. Regional impacts: risks to health and ecosystems

4.1 Acid rain

The term acid rain refers to the deposition of acidifying species on the ground: wet deposition of pollutants incorporated into precipitation (rain, snow, fog, etc.), dry deposition of gases and particles. The pollutants that cause acid rain are sulfur and nitrogen compounds. These gases chemically evolve in the air to form acids or their salts, which are found in clouds and precipitation. These compounds are also deposited on the ground, after possible chemical transformation, in the form of dry...