Acid Deposition on Forest - Case Study Example

Acid Deposition on Forests Acid deposition can be defined as deposition of harmful chemicals such as sulphur dioxide and nitrogen oxides emissions. The oxides get converted to moist secondary pollutants such as sulphuric acid, nitric acid and ammonium nitrate. Acidic deposition occurs “Sulfur and nitrogen containing species along with reactive hydrocarbons are emitted from a variety of anthropogenic and natural sources. These compounds are mixed, transported, reacted, and finally removed back to the earth’s surface.”(Carmichael, Arndt. pp. 1-2). These pollutants can be transported over a large area. Acidic deposition can occur in two ways such as wet deposition and dry deposition. Dry deposition is the form of acid deposition in which dry particles such as fly ash, sulphates, nitrates and sulphur and nitrogen oxides are deposited on the surfaces. These particles get absorbed to the surface and might later turn to acids when they are in contact with water. Wet deposition is a process by which the oxides come in contact with rain or moisture and get transformed to acids. Those acids whose pH is less the 5.5 are removed from the atmosphere by rain, snow or hail. The wet deposition of acids through rain is acid rain. “Acid rain or acid deposition, form of precipitation (rain, snow, sleet or hail) containing high levels of sulphuric or nitric acids (p H below 5.5-5.6)” (The Columbia Encyclopaedia, 2008. Para1) Acid deposition can pollute soil, air, water etc. and hence affect the environment. Emission of sulphur dioxide and nitrogen oxides can pollute a place which is in another geographic area, as these gases get carried away by wind. In 1980, Canada stated that the emissions from United States are contaminating forests and waters in Canada. After this, U.S Clean Air Act was enacted to reduce the sulphur dioxide emissions from power plants. Even though there are many pollutants emitted in air, the main pollutants that cause acid rain are Sulphur dioxide and Nitrogen oxides. Forms of Acid Deposition The sulphur dioxide is emitted by metal smelters, power plants and industrial combustion sources. Nitrous oxide is emitted by vehicles, power plants and industrial combustion sources. Fig: 1, Origin of acid deposition, Source: Wikipedia Smelting: Smelting is a process by which pure metal is extracted from its ore. In the process there will be slag, the solid metallic waste and emissions of gases such as sulphur dioxide, which is the main source of acid rain. When the sulphide ores are smelted, sulphur dioxide gas is produced which reacts with atmosphere to form a mist of sulphuric acid which comes down as acid rain. Sudbury is one of the world’s largest smelting complexes in Canada. Sulphur dioxide emission from the plant caused acid deposition through acid rain and vegetation over 46,000 hectares had been bared. Efforts by Governments through clean air act, has effectively curbed such emissions. (Pollution Issues) Vehicular transport: Vehicular transport mainly constitutes to nitrogen oxide emissions in the atmosphere. Nitrogen oxides are produced when engines run at a high temperature and pressure, causing the reaction of nitrogen and oxygen. These nitrogen oxides produced are the cause of nitric acid rain and dry deposition of gases in soil. Even though catalytic converters have reduced the emission, the increase in the number of vehicles now leads to pollution and acid deposition. Power plants: Acid deposition is also caused by power plants. Power plants run on fossil fuels. The combustion of the fossil fuels causes smog, acid rain and climate change. The power plants use air during the combustion process which results in the formation of sulphur dioxide, nitrogen oxides and other gases. These gases are released in the atmosphere through chimneys. These gases get deposited in the higher altitudes and cause acid deposition over a larger area. Industrial boilers: Industrial boilers also use fossil fuels for burning and heating purposes. This causes emission of harmful oxides of sulphur and nitrogen. Dry deposition of oxides, wet deposition of oxides in the form of acids, both pollutes the environment. Effects of Acid Rain The acid deposition either wet or dry affects the pH of the soil, causes water pollution, affects the forests, creates health problems etc. There occurs both long term and short term effects of wet deposition of acids in the soil. Short term effects of acid rain: The short term effects of acid rain in forests leads to deposition of nitrates in the soil. This might initially increase the soil fertility as nitrogen is the most needed nutrient for trees to grow in a soil, thereby increasing the growth of trees. With respect to the research based on simulated acid rain (Bormann, Wood) it was found that the seedling productivity increased with rain water acidity. This is due to nitrates deposited in the soil. This productivity was due to increase in nitrogen content along with the presence of Calcium, Potassium and Magnesium ions in the soil. This however is a short-term phenomenon as leaching of cations beyond a certain amount will affect the composition of the soil. Nitrogen stimulates the growth but alone cannot support growth without the presence of cations. Long term effects of acid rain: Research done based on the long-term data from the Hubbard Brook Experimental forest; New Hampshire (Likens, Buso, Driscoll 1996, p.245) has concluded that …forest ecosystems are much more susceptible to continuing atmospheric inputs of strong acids than expected on the basis of trends in sulphur biogeochemistry alone. The long-term hysteresis pattern in streamwater chemistry suggests that ecosystem acidification may be reversible, but recovery is very slow. Acid deposition has caused the decline of red spruce trees throughout the eastern United States, Sugar Maple trees in central and western Pennsylvania and trees growing in higher altitudes. The deposition caused poor crown conditions, reduced growth in trees thereby triggering mortality of trees. In case of spruce, due to leaching of calcium ion, the trees’ tolerance level to low temperature is considerably reduced which causes its subsequent death. High aluminium concentration in soils would have reduced its absorption of water and nutrients through roots. With respect to study made on decline of sugar maple, the decline is attributed to deficiency of cations such as calcium and Magnesium in the soil and foliage and high stress on the plant from insect defoliation and drought. The low level of cations occurs due to acid deposition. This can cause nutrient imbalance in trees which in turn reduces the susceptibility of trees to insect infestations and drought. Acid rain causes depletion of basic cations which causes nutrient imbalance and disturbance in soil processes. This may in turn affect the recovery of the sensitive soil (The Encyclopedia of Earth [EoE], 2010). On a long term basis it will lead to death of forest trees. Solutions and Best Practices to Reduce Acid Rain Reduction of acid rain involves the reduction of the emission of sulphur dioxide and nitrogen oxides in the atmosphere. Individual Government, Organisation should come forward in providing a cleaner air to the people. Government regulations will help in curbing the amount of gases emitted in the atmosphere. Individual efforts towards limited use of vehicles or pooling will also reduce the emission. Organisations can come forward to put filters or take efforts to reduce the emission of gases. Reduction in Sulphur dioxide: Sulphur dioxide plays a major part in producing acid rain. The United States passed Clean Air Act. This act was passed to reduce the emission of sulphur dioxide and nitrogen oxide gases in the atmosphere and to provide a clean air. In 1990, the act was amended to control emissions of sulphur power plants. The Clean Air Interstate Rule (CAIR) passed by EPA in 2005 provides solution to the power plant pollution that drifts from one state to another. Fig. 2 Sudbury Annual Sulphur dioxide emission. Source: Pollution Issues The figure 2 shows the reduction in the emission of Sulphur dioxide in the atmosphere since 1970. It can be seen that government regulations has achieved the needed result in reducing the emission. The United States, European Union have reduced the emission of sulphur dioxide in air drastically. Figure 3 shows the increase in emission of sulphur dioxide in Asia Owing to its fast pace of development, the emission from China being the maximum. Fig: 3 Past and Projected Sulphur dioxide emissions for Europe, the United States and Canada, and Asia. Source: Downing et al. 1997 (MyEcoProject) In order to reduce the emissions, various technologies can be applied such as “end-of-pipe” and burner modification emission control technologies, fuel processing technologies, fuel-switching measures, and energy-efficiency technologies and measures. (Hippel, 1996, Technologies for reduction of acid gas emissions, Para 2). Reduction in Nitrogen Oxides: Nitrogen oxide emissions occur from vehicular transport, power plants, fertilisers run off, animal waste from farms, discharge from sewage treatment plants and industrial facilities. The catalytic converters are used in vehicles to decrease the pollution. Even then the emissions from vehicles have become a major source of nitrogen oxides in the atmosphere because of the increase in number of vehicles .Excess nitrogen oxide deposition causes reduction in tree population in forests. Frequent emission check and servicing would help in curbing acid rain. Next to vehicular pollution, agriculture plays an important role in releasing nitrogen in the atmosphere. Use of organic fertilisers and controlling the use of pesticides, will help in reducing the acid deposition. Conclusion There have been so many regulations and many acts passed in consideration to the acid deposition in the atmosphere. The contribution towards acid rain has reduced considerably in developed nations, than in developing nations. North East Asian nations are developing in a tremendous pace that the care towards the environment takes the back seat. According to a report, If current (1990) emission control requirements in the region remain unchanged in the future, it is estimated that there will be a 175% increase in SO2 emissions and a 250% increase in NOx emissions between 1990 and 2020. There is no doubt that this would seriously exacerbate the acid rain problem in the region, with growing amounts of pollution transported from Northeast China across to the Korean peninsular and to Japan. (Streets, 1997, Para 6). Thus, it is extremely essential that all the countries through out the world take precautions, follow the regulations and acts imposed and join hands in saving the environment and the ecosystem as a whole. References Acid rain. (2008). The Columbia Encyclopedia, Sixth Edition. Retrieved December 01, 2010 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-acidrain.html AILSA ALLABY and MICHAEL ALLABY (1999). Acid rain. A Dictionary of Earth Sciences. Encyclopedia.com. 1 Dec. 2010 . Bormann F.H., Wood, Tim (n.d.). Short term effect of a simulated acid rain upon the growth and nutrient relations of Pinus Strobus, L. Water, Air and Soil Pollution, Vol. 7, 479-488. Doi: 10.1007/BF00285546. Retrieved from http://www.springerlink.com/content/p856g301638g7u72/. (2010, December 03) Buso, D.C. Driscoll, C.T. Likens, G.E. (1996). Long-Term Effects of Acid Rain: Response and Recovery of a Forest Ecosystem. Science New series Vol.272 (5259), 244-246. Retrieved from http://www.esf.edu/efb/mitchell/Class%20Readings/Sci.272.244.246.pdf. (2010 December 03) Carmichael, R. Gregory, Arndt, Richard, (n.d.). Baseline Assessment of Acid Deposition in Northeast Asia. Retrieved from http://oldsite.nautilus.org/archives/papers/energy/CarmichaelESENAY1.pdf. (2010 December 03) Hippel, David Von (1996). Technological Alternatives to Reduce Acid Gas and Related Emissions from Energy-Sector Activities in Northeast Asia. Retrieved from http://oldsite.nautilus.org/archives/papers/energy/dvhtech.html My Eco Project. (n.d.). Acid Rain Causes and Effects. [Weblog]. Retrieved from http://myecoproject.org/get-involved/pollution/acid-rain/. (2010, December 3). Pollution Issues. (n.d.). Smelting. Retrieved from http://www.pollutionissues.com/Re-Sy/Smelting.html, (2010, December 03) Streets, G. David (1997). Energy and Acid Rain Projections for Northeast Asia. Message posted to http://oldsite.nautilus.org/archives/fora/energy/9713A_Streets.html Wikipedia. Acid Rain (n.d.). Retrieved from the Wikipedia: http://en.wikipedia.org/wiki/Acid rain. Read More