• the deposition of acidic components in rain, snow, dew, or dry particles.
• more accurate term is "acid precipitation."
• defined as any type of precipitation with a pH that is unusually low
The Causes:
• occurs when sulfur dioxide and nitrogen oxides are emitted into the atmosphere, undergo chemical transformations and are absorbed by water droplets in clouds
• then fall to earth as rain, snow, mist, dry dust, hail, or sleet.
• Dissolved carbon dioxide dissociates to form weak carbonic acid giving a pH of approximately 5.6 at typical atmospheric concentrations of CO2
• Therefore a pH of less than 5.6 has sometimes been used as a definition of acid rain
The Effects:
• increases the acidity of the soil, and affects the chemical balance of lakes and streams
• accelerates weathering in carbonate rocks and accelerates building weathering
• contributes to acidification of rivers, streams, and forest damage at high elevations
• When the acid builds up in rivers and streams it can kill fish
Problems:
• large fraction of which are formed from the same gases as acid rain (sulfur dioxide and nitrogen dioxide), have been shown to cause illness and premature deaths such as cancer and other deadly diseases
• killing off insect and aquatic lifeforms as well as causing damage to buildings and having possible impacts on human health
• cause damage to certain building materials and historical monuments
• cause weathering on ancient and valuable statues and has caused considerable damage
• sulfuric acid in the rain chemically reacts with the calcium compounds in the stones (limestone, sandstone, marble and granite) to create gypsum, which then flakes off
• commonly seen on old gravestones where the acid rain can cause the inscription to become completely illegible
• causes an increased rate of oxidation for iron
• Visibility is also reduced by sulfate and nitrate in the atmosphere
Solutions:
• many coal-burning power plants use Flue gas