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Pollution from the internal combustion engine.

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In the process of internal combustion, numerous substances are released that are potentially of great damage to the environment. Here we shall be looking at > the processes in which the harmful outputs are formed, > effects of their output, often linked with > major global issues such as acid rain. When discussing such issues only the effects of exhaust gases from internal combustion are included. CONTENTS - PAGE 1 - Carbon Dioxide - Global Warming - Carbon Monoxide - PAGE 2 - Hydrocarbons - Oxides of Nitrogen - PAGE 3 - Ozone Layer - Oxides of Sulphur - Acid Rain - Lead Carbon Dioxide, CO2 is formed during internal combustion in engines using oil related fuel, especially when the three way catalyst oxidises Carbon Monoxide, CO, converting it into CO2. The source of carbon is the carbon-containing compounds from the fuel input, which fully oxidise. Carbon Dioxide does not directly harm the human body. However, it has a great role in the process of global warming and is considered as the key "greenhouse gas" - its contribution to global warming is 57%. This is because it is a great absorber of Infra Red radiation that is emitted towards the space from the earth surface. Methods of reducing CO2 emissions are by either improving the heat efficiency of engines thus reducing the amount of fuel consumption, or by using alternative fuels not related to oil. ...read more.


A final source is from incomplete combustion due to bulk quenching of the flame in the fraction of the engine cycles where combustion is slow. These conditions are most likely to take place when the air:fuel ratio, spark timing and fraction of the exhaust recycled for emission control may not be well matched. Problems of Unburned Hydrocarbons Unburned hydrocarbons often result in great problems due to association with oxides of nitrogen, another exhaust gas of the internal combustion engine, discussed later. It can form ozone with oxides of nitrogen, which is a central nervous system depressant, and other hydrocarbons can cause the convulsion of CNS. This association with oxides of nitrogen not only contributes to destruction of the ozone layer but also causes photochemical smog - which is a possible key cause of melanoma, a form of cancer. Arguably the oxides of nitrogen, collectively represented formulaically as NOx, can be considered as the most harmful of the exhaust gases resulting from internal combustion because their affects can be seen in a variety of areas. Nitric oxide, NO, forms throughout high temperature burned gases behind the flame through chemical reactions involving the 2 elements that do not achieve chemical equilibrium. The higher the temperature of burned gas, the higher the rate of nitric acid formation. So when combustion is done in the area closer to the theoretical air:fuel ratio, the Stoichiometric ratio, more nitric oxide is released as it is closer to complete combustion. ...read more.


It can turn leaves yellow and decreases the growth rate of crops. Lead, Pb, is sometimes an output of internal combustion - it is not a natural compound of fuel but is often added to petroleum for the molecules to act as branched chains as this is more cost effective (in the short term). There are many problems associated with lead input so now Unleaded fuel is a more common alternative and the development of Lead Replacement Fuel is hoping to decrease the effects of lead. Problems are mainly for humans - when there is a great proportion of lead, the body mistakes lead for calcium when ingested which can disrupt functioning enzymes. The effects of this include disabilities, heart and kidney disease, neurological deficits and strokes. 3 quarters of ingested lead is deposited in bones and tissues causing irreversible brain and kidney damage - particularly vulnerable are young children who have a growing nervous system. Conclusion In general, the amount of emissions from car engines is rising year by year as developing countries become more industrialised, and capitalist areas such as USA use private transport more and more. However there are measures to control all of the global issues, such as United Nations Sulphur Protocol giving limits to a country's sulphur emissions in a year. Also the harmful gases such as Carbon Monoxide and Nitrogen Dioxide can be made harmless by reacting the two substances with use of a catalytic converter. ...read more.

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