Acid rain contains acids that form up in the atmosphere when gas emissions such as, nitrous oxide and sulfur oxide combine with water vapour. About 70% of acid rain comes from sulfur dioxide (SO2) which dissolves into water (H2O) to form sulfuric acid. The rest of the gasses come from nitrous oxides (NOx) which are made up of various forms of nitrogen (NO2 + NO3). These gasses are caused by burning fossil fuels mainly coming from power stations and motor transport. .
Acid rain causes acidification of lakes and streams and contributes to damage of trees, soils and living organisms which live in the earth and lakes. Acid rain accelerates the rotting of building materials. Prior to falling to the earth, sulfur dioxide (SO2) and nitrous oxide (NOx) gases contribute to poor visibility and harm public health.
Acid rain has two varieties of deposition: wet and dry. Wet deposition relates to acidic rain, fog and snow. Whilst acidic water flows over and across the ground, it affects a variety of plants and animals. The intensity of the effect relies on many elements, including how acidic the water is, the chemistry and insulating capacity of the soils affected, and the types of fish, trees, and other living things that depend on water. Dry deposition relates to acidic gasses and particles. Approximately half of the acidity particles in the atmosphere dries and falls back to earth. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. When this happens, the wasted water adds to those acids to the acid rain, making the mixture more acidic than the falling rain alone.
Because acidic pollution is transboundary, there is no clear relationship between how much pollution a country emits and how much is deposited there. Throughout Europe, the dominating wind direction is mostly westerly or southwesterly. Therefore, much of the pollution is emitted in the UK and travels across the North Sea and is deposited in Scandinavia.