Air Pollution From Automobiles Is A Major Environmental And Health Problem In Ma

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Term Paper Title	Air Pollution From Automobiles Is A Major Environmental And Health Problem In Ma
# of Words	1479
# of Pages (250 words per page double spaced)	5.92

Air pollution from automobiles is a major environmental and health problem in many cities across the United States and around the world.  Air pollution comes from the comes from the combustion process that leave the engine through the exhaust system and the crankcase. In engines using unleaded gasoline, the compounds in the exhaust are typically hydrocarbons, carbon monoxide, and oxides of nitrogen in diesel engines.  The exhaust includes particulates that are related to smoke, and in engines using alternative fuels such as methanol, exhaust also includes volatile organic compounds such as formaldehyde.
Exhaust emissions are a function of engine operation.  For example, compression ratio, temperature, spark timing, air fuel ratio, and engine speed all effect what hydrocarbons are produced.  Hydrocarbons in the exhaust are unburned or partially burned fuel and oil.  Carbon monoxide is formed in the combustion process and is always preset in small quantities in the exhaust regardless of the air fuel ratio.  The greater the proportion of fuel there is in the air fuel mixture, the more carbon monoxide is produced.  Oxides of nitrogen are formed during the combustion process, increasing with peak combustion temperature and pressure, and are also a function of the air fuel ratio.
Automotive pollutants, directly and indirectly have adverse health effects, and their discharge into the atmosphere has been subject to regulatory control over two decades.  Exhaust emissions can be limited by a variety of means.  Exhaust gases that escape past the piston rings into the crankcase are drawn back into the engine using a positive crankcase ventilation system, and the unburned hydrocarbons are combusted.  Emissions released through the exhaust pipe are controlled in virtually all vehicles today by three way catalytic converters in the exhaust system and by electronic controls on gasoline powered engines.  The introduction in 1978 of the three way catalyst marked a major stride in emissions control technology because it enabled the limitation of nitrous oxide and carbon monoxide emissions to levels in compliance with current standards.
Hydrocarbon emissions from the fuel system that occur while the car is in operation or while parked are controlled using a carbon (charcoal) canister that absorbs the vapors.  Such controls have been in use since 1975.  Hydrocarbon losses during refueling when vapor is displaced from the fuel tank by the entering of liquid, can be controlled...

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