24-03-2012, 03:05 PM
Acid Rain
AcidRain.ppt (Size: 1.55 MB / Downloads: 162)
Definition of Acid Rain
Precipitation that has a pH of less than that of natural rainwater (which is about 5.6 due to dissolved carbon dioxide).
It is formed when sulphur dioxides and nitrogen oxides, as gases or fine particles in the atmosphere, combine with water vapour and precipitate as sulphuric acid or nitric acid in rain, snow, or fog.
Natural Sources
Emissions from volcanoes and from biological processes that occur on the land, in wetlands, and in the oceans contribute acid-producing gases to the atmosphere
Effects of acidic deposits have been detected in glacial ice thousands of years old in remote parts of the globe
The principal cause of acid rain is from human sources
Industrial factories, power-generating plants and vehicles
Sulphur dioxide and oxides of nitrogen are released during the fuel burning process (i.e. combustion)
Harmful to vegetation
Increased acidity in soil
Leeches nutrients from soil, slowing plant growth
Leeches toxins from soil, poisoning plants
Creates brown spots in leaves of trees, impeding photosynthesis
Allows organisms to infect through broken leaves
Flue Gas Desulphurisation (FGD)
Removes sulphur dioxide from flue gas (waste gases)
Consists of a wet scrubber and a reaction tower equipped with a fan that extracts hot smoky stack gases from a power plant into the tower
Lime or limestone (calcium carbonate) in slurry form is injected into the tower to mix with the stack gases and reacts with the sulphur dioxide present
Liming
Powdered limestone/limewater added to water and soil to neutralize acid
Used extensively in Norway and Sweden
Expensive, short-term remedy
AcidRain.ppt (Size: 1.55 MB / Downloads: 162)
Definition of Acid Rain
Precipitation that has a pH of less than that of natural rainwater (which is about 5.6 due to dissolved carbon dioxide).
It is formed when sulphur dioxides and nitrogen oxides, as gases or fine particles in the atmosphere, combine with water vapour and precipitate as sulphuric acid or nitric acid in rain, snow, or fog.
Natural Sources
Emissions from volcanoes and from biological processes that occur on the land, in wetlands, and in the oceans contribute acid-producing gases to the atmosphere
Effects of acidic deposits have been detected in glacial ice thousands of years old in remote parts of the globe
The principal cause of acid rain is from human sources
Industrial factories, power-generating plants and vehicles
Sulphur dioxide and oxides of nitrogen are released during the fuel burning process (i.e. combustion)
Harmful to vegetation
Increased acidity in soil
Leeches nutrients from soil, slowing plant growth
Leeches toxins from soil, poisoning plants
Creates brown spots in leaves of trees, impeding photosynthesis
Allows organisms to infect through broken leaves
Flue Gas Desulphurisation (FGD)
Removes sulphur dioxide from flue gas (waste gases)
Consists of a wet scrubber and a reaction tower equipped with a fan that extracts hot smoky stack gases from a power plant into the tower
Lime or limestone (calcium carbonate) in slurry form is injected into the tower to mix with the stack gases and reacts with the sulphur dioxide present
Liming
Powdered limestone/limewater added to water and soil to neutralize acid
Used extensively in Norway and Sweden
Expensive, short-term remedy