Acid rain is basically defined as any kind of precipitation that has a pH-level lower than 5.5 (? 5.5), meaning that is more acidic than the usual precipitation. Precipitation is by nature already slightly acidic, because of the natural carbon dioxide in our atmosphere gets dissolved into the rain. The aqueous solution of CO2 is than Carbonic acid, H2CO3: Co2 + H2O – H2CO3. H2CO3 is as an aqueous solution not stable, and thus it ionizes into water, forming the ions H3O+ and HCO3-: CO2 + H2O – HCO3- + H3O+.When the precipitation, which can be for example rain, snow or fog, has a pH-level lower than 5.5 it is considered acidic and is due to human output of nitrogen and sulphur compounds.
They both go through many complex steps until they become sulphuric acid (H2SO4) and Nitric acid (HNO3), which one would find in Acid rain. sulphuric acid originates from its compound. The sulphur dioxide reacts with Oxygen to make sulphur trioxide: 2SO2 +O2 -> 2SO3. Than the sulphur trioxide reacts with water to make sulphuric acid: SO3 + H2O -> H2SO4. Nitric acid is made when nitrogen dioxide reacts with water, which also makes nitrous acid. The pH-level of an acidic rain cloud can reach up to 2.6. In areas with a lot of industry the pH-level will be about 4; in Los Angeles the most acidic precipitation had a pH-level of 3. However, in some parts of the world, such as north Australia, natural emissions of the vegetation can make the pH sink to 4.4.
The cause of nitrogen oxide, sulphur dioxide, ammoniac and other compounds being in our rain is the burning of fossil fuels. Humans release about 3.5 million tons of SO2 into our atmosphere a year. Especially when coal and petroleum is burned, a lot of SO2 -released. Power plants, cars, ships und planes are all sources of NO and SO2. The main natural contributor to acid rain are volcanoes. They release about 230 billion metric tons (230 teragrams) of carbon dioxide a year. How much percent of the emissions caused by humans and how is caused by nature depends on the area. In cities up to 90% of the emissions can be caused by humans, but in other regions it could be 50% to 50%.The acid rain is global problem and has many different affects all around the world. The damage to buildings is only one of them.
The acidic rain gets into the stone of the building and starts a chemical reaction, in which the stone starts to decompose. This makes the buildings more fragile to water, frost and other things that the stone would normally be able to withstand. The acid rain has destroyed many precious memorials that were made out of natural stone. The acid rain destroys the whole outer layer of the stone, which will make the fine carvings into the stone vanish. Limestone and marble are especially affected by acid rain, because they consist out of calcium carbonate. The calcium carbonate reacts with the dissolved acids than form plaster, which gets flakes after every new rain fall: CaCO3 + H2SO4 ï¿½ CaSO4 + CO2 + H2O.
The restoration of damaged building takes a lot of time and money. For example the restoration of the Westminster Abbey in London cost up to 10 million pounds. They had to peal of the damaged outer layer of the stone and than treat the new healthy outer layer of stone with a special fluid that is supposed to stop the acid rain from getting on into the stone again. (1,3, 4, 8)
In Scandinavia the acid rain has been destroying the nature for decades. Many lakes are acidic, meaning that they have an unusually low pH-level caused by the acid rain being collected in the lake. At some point there were about 14000 lakes acidic. The water in the lakes is clear; one can see the ground of the lake, but biologically they are dead. This had many affects on the surrounding plants and animals they were also poisoned. The UK, the Alps and north America are having similar problems. The acid rain in Scandinavia also causes ground acidity. This affects the fertility of the soil. Important nutrients, such as Ca or Mg, get washed away by the acid rain before the plants can use for growth.
Also Aluminum (Al3+) is released. This kind of aluminum is poisonous to plants; it damages the root hair of the plants and reduces the absorption of phosphor and other important nutrients. Many trees die from malnutrition and a weak defense mechanism. Soil that is already on slightly acidic bedrock will suffer from severe problems, on the other hand soil that is on calcareous bedrock will benefit from the acid rain. Acid rain can also directly damage the nature, instead of, for example, triggering a chemical reaction or to prevent the absorption of nutrient, which are harming the nature indirectly. If the plants are near strong emission source, such as power plants without a filter system, there will be a lot of SO2 in the air. The SO2 will destroy the surface of needles and leaves, which will result in uncontrolled water loss and the prevention of photosynthesis. (10, 6)
The Acid rain also affects the economy of the Scandinavian countries. Two major industries are the forestry and fishery. When the pH-level in the waters drops below 5.5 the fish will have to suffer from permanent damage. This occurred especially in the 1950s, in the southern lakes and rivers. High concentrations of Aluminum, which were washed out of the ground by the acid, were the main cause of the dying fish. The Aluminum reduces the ionic transportation through the gill and causes a lack of salts. It is vital for Sweetwater fishes to sustain their Osmoregulation. Osmoregulations is the balance of salts and minerals in the tissue of the fish.
The aluminum will get stuck in the gills and prevents the vital transportation of salts and oxygen, meaning that the fish will not be able to regulate its body salts. The fishing industry plays a very important role in the economy of the Scandinavian countries. In Norway, for example, over 26000 people have jobs in the fishing industry and in only one year the aquaculture industry was able to produce 2.1 million of fish, of which 90% were exported. The other big industry is forestry. In Norway 8,868,000 ha is forestland. With the export of wood about 804million dollars were earned. If the Acid rain were to continue it will start to have tremendous effects on the economy of Scandinavia. More trees and fish will be killed and thus less will be available to be exported. (7, 5)
Several methods have been tried to solve the environmental problem that our industry’s pollution has caused. There have been only a few attempts to fight the symptoms, the symptoms being the damage to the environment. Large forest areas and many lakes have been treated with Calcium Carbonate. This procedure is called liming, where CaCO3 is either sprayed over forest and lakes to neutralize the acidity that was caused by the acid rain. Especially Norway and Sweden have used this procedure bring back life in all the otherwise life-less lakes. However it is only a short-term solution, as it does not stop the acid rain and thus huge amounts of limestone would have to be deployed very frequently. This does not only cost a lot of money, it is not even clear whether, besides neutralizing the acidity, the CaCO3 has any other, maybe negative, effects on us and the plants. The only long-term solution would be to reduce the amount of Sulphur Dioxide and Nitrogen oxides emitted into the atmosphere.
One way would be to use less fossil fuels, as when burnt they release large amounts of both SO2 and NOx. Using more alternative energy would reduce the emissions, as in the procedure no SO2 or NO is released. However when they are burnt devices named scrubbers should be used; they reduce the emissions by removing the SO2 out the gases. In the end, none of the technology will be able to help us if we are not able to reduce the amount of energy usage from fossil fuels. If everybody would make only small changes, such as taking the bus instead of the car, turning off things when they are not needed or use more energy efficient machines, we would be able to save a lot of energy. This would have several benefits, one of them many being able to stop acid rain destroy our nature. (9, 3, 6)
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