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Acid deposition
- 2. - the accumulation of acids or acidic compounds on the surface of the Earth, in lakes or streams, or on objects or vegetation near the Earth's surface, as a result of their separation from the atmosphere.
- 4. - is caused by carbon dioxide (CO2 ) , nitric oxide (NO), and sulfur dioxide (SO2)
- 8. MAIN SOURCES: 1. Natural emissions 2. Anthropogenic
- 9. NOx
- 10. SO2
- 11. EFFECTS OF ACID DEPOSITION: 1. On Forests: - improves soil condition by supplying essential chemicals for soil nutrition
- 12. EFFECTS OF ACID DEPOSITION: 1. On Forests: - causes slower growth, injury, or death of forests by leaching the buffering agents in the soil - causes the release of substances that are toxic to trees and plants, such as aluminium, into the soil.
- 13. EFFECTS OF ACID DEPOSITION: 2. On Waters and Aquatic Organisms - causes a cascade of effects that harm or kill individual fish, reduce fish population numbers, completely eliminate fish species from a waterbody, and decrease biodiversity.
- 14. EFFECTS OF ACID DEPOSITION: 3. On Materials/Sculptures/Buildings -causes extensive damage to building, statues, bridges, & structural materials of marble, lime stone, sandstone, mortar.
- 15. AFFECTED AREAS Places significantly impacted by acid rain around the globe include most of eastern Europe from Poland northward into Scandinavia, the eastern part of the United States, and southeastern Canada. Other affected areas include the southeastern coast of China and Taiwan.
- 16. 1. Flue-gas desulfurization (FGD) to remove sulfur-containing gases from their stack gases. 2. Fluidized bed combustion. 3. Coal washing (to remove sulfur before burning)
- 17. 4. Fit catalytic converters to vehicle exhausts which remove the nitrogen oxides. 5.Reduce the amount of electricity we use. 6. Limit the number of vehicles on the roads and increase public transport. 7. Use renewable energy like wind power, solar panels, tidal power.
- 18. ”Saying sulfatesdo not cause acid rain is the sameas saying that smoking does not cause lung cancer.”
Editor's Notes
- transboundary environmental problem
- Acid rain refers to rainfall that has a pH lower than 5.65.
- Diluted forms of these acids, and other substances, can fall to earth as rain, snow, sleet, hail, or fog. When it is not raining, the oxides interact directly with soil, vegetation and water in a variety of ways referred to as dry deposition. NO (Nitrogen oxide) Dry- can be responsible for as much as 20 to 60% of total acid deposition. occurs when particles and gases stick to the ground, plants or other surfaces. Acid rain refers to rainfall that has a pH lower than 5.65.
- *natural, unpolluted rainwater actually has a pH of about 5.6 (acidic) The acidity of rainwater comes from the natural presence of three substances (CO2, NO, and SO2) found in the troposphere (the lowest layer of the atmosphere). carbon dioxide (CO2) is present in the greatest concentration and therefore contributes the most to the natural acidity of rainwater. Globally, about 40% of total N2O emissions come from human activities. [1] Nitrous oxide is emitted from agriculture, transportation, and industry Carbon dioxide, produced in the decomposition of organic material, is the primary source of acidity in unpolluted rainwater. Although CO2 is present in a much higher concentration than NO and SO2, CO2 does not form acid to the same extent as the other two gases. Thus, a large increase in the concentration of NO and SO2 significantly affects the pH of rainwater, even though both gases are present at much lower concentration than CO2.
- Carbon dioxide reacts with water to form carbonic acid (Equation 1). Carbonic acid then dissociates to give the hydrogen ion (H+) and the hydrogen carbonate ion (HCO3-) (Equation 2). The ability of H2CO3 to deliver H+ is what classifies this molecule as an acid, thus lowering the pH of a solution.
- Nitric oxide (NO), which also contributes to the natural acidity of rainwater, is formed during lightning storms by the reaction of nitrogen and oxygen, two common atmospheric gases (Equation 3). In air, NO is oxidized to nitrogen dioxide (NO2) (Equation 4), which in turn reacts with water to give nitric acid (HNO3) (Equation 5). This acid dissociates in water to yield hydrogen ions and nitrate ions (NO3-) in a reaction analagous to the dissociation of carbonic acid shown in Equation 2, again lowering the pH of the solution.
- Sulfur dioxide, like the oxides of carbon and nitrogen, reacts with water to form sulfuric acid Sulfuric acid is a strong acid, so it readily dissociates in water, to give an H+ ion and an HSO4- ion (Equation 7). The HSO4- ion may further dissociate to give H+ and SO42- (Equation 8). Thus, the presence of H2SO4causes the concentration of H+ ions to increase dramatically, and so the pH of the rainwater drops to harmful levels. SO2 + H2O —> H2SO3
- NATURAL - volcano emissions, lightning, and microbial processes(Ammonia may act as a base in the atmosphere, neutralizing nitric and sulfuric acid, but ammonia in soil or groundwater is, to a large extent, converted by microorganisms into nitric acid, producing additional acid in the process. ) ANTHRO – transportation, industrial emissions , combustion of fossil fuel, and electric utilities. When nitric and sulfuric acids are released into the atmosphere by smokestacks, fuel combustion, they mix with water vapor at unusual proportions to cause acid deposition. 67% is anthro. (Human emissions are approximately twice as much as natural ones)
- Acid Rain dissolves all the nutrients and the useful minerals for the tree to grow. The ability of forest soils to resist, or buffer, acidity depends on the thickness and composition of the soil, as well as the type of bedrock beneath the forest floor. buffer capacity is the amount of acid or base a buffered solution can soak up before its pH will start to change significantly. At high pH, calcium, magnesium and potassium oxides, together with carbonates, help to buffer pH changes; at acidic pH, aluminum oxides and iron hydroxides act as buffering agents Degradation of many soil minerals produces metal ions that are then washed away in the runoff, causing several effects:The release of toxic ions, such as Al3+, into the water supply. The loss of important minerals, such as Ca2+, from the soil, killing trees and damaging crops. Acid Rain leaches potassium, calcium, magnesium, etc essential elements from the top of soil
- These buffering agents, such as calcium and magnesium salts, are essential to protecting the forest life from the harmful effects of acid deposition. Once they are removed, aluminum ions are dissolved from minerals and released into the soil environment. The combination of the toxic aluminum and disappearing calcium results in stunted tree growth. Either forests die off or new acid-tolerant species gradually replace the previous ones. The ability of forest soils to resist, or buffer, acidity depends on the thickness and composition of the soil, as well as the type of bedrock beneath the forest floor. Acid Rain leaches potassium, calcium, magnesium, etc essential elements from the top of soil buffer capacity is the amount of acid or base a buffered solution can soak up before its pH will start to change significantly. Leaching- a process in which acid deposition adds hydrogen ions which displaces important nutrients like Calcium, Magnesium, and Potassium. Leaching pushes the ions deeper in the soil so the plants roots can’t reach them. Leach - to drain away from soil when dissolved in rainwater, Buffering agents - aluminum oxides and iron hydroxides At high pH, calcium, magnesium and potassium oxides, together with carbonates, help to buffer pH changes; at acidic pH, aluminum oxides and iron hydroxides act as buffering agents Base Nutrient Depletion…Aluminum Toxicity…Nitrogen Saturation:…Eutrophication (nutrient enrichment)
- Acid rain flows into streams, lakes, and marshes after falling on forests, fields, buildings, and roads. Acid rain also falls directly on aquatic habitats As acid rain flows through soils in a watershed, aluminum is released from soils into the lakes and streams located in that watershed. So, as pH in a lake or stream decreases, aluminum levels increase At pH 5, most fish eggs cannot hatch. At lower pH levels, some adult fish die. Fish usually die only when the acid level of a lake is high; when the acid level is lower, they can become sick, suffer stunted growth, or lose their ability to reproduce
- Famous buildings like the Statue of Liberty in New York, the Taj Mahal in India and St. Paul's Cathedral in London have all been damaged by this sort of air pollution. MORTAR- grout Acid rain also increases the corrosion rate of metals, in particular iron, steel, copper and bronze.
- An example of FGD is the wet scrubber which is commonly used. A wet scrubber is basically a reaction tower equipped with a fan that extracts hot smoke stack gases from a power plant into the tower. Lime or limestone in slurry form is also injected into the tower to mix with the stack gases and combine with the sulfur dioxide present. The calcium carbonate of the limestone produces pH-neutral calcium sulfate that is physically removed from the scrubber. That is, the scrubber turns sulfur pollution into industrial sulfates.
- An example of FGD is the wet scrubber which is commonly used. A wet scrubber is basically a reaction tower equipped with a fan that extracts hot smoke stack gases from a power plant into the tower. Lime or limestone in slurry form is also injected into the tower to mix with the stack gases and combine with the sulfur dioxide present. The calcium carbonate of the limestone produces pH-neutral calcium sulfate that is physically removed from the scrubber. That is, the scrubber turns sulfur pollution into industrial sulfates. Fluidized bed combustion- is a combustion technology used in power plants