Air pollution from automobiles is a major environmental and health pro
"Has been a lifesaver so many times!"
- Catherine Rampell, student @ University of Washington
"Exactly the help I needed."
- Jennifer Hawes, student @ San Jose State
"The best place for brainstorming ideas."
- Michael Majchrowicz, student @ University of Kentucky
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 either by returning vapor from the vehicle to the service station tank or by using a larger carbon canister on the vehicle that traps the fuel vapors. Stage two controls on fuel pumps in service stations are already used in some jurisdictions, and on board control is contemplated, but it is currently not required.
The conventional gasoline powered engine in all automobiles sold today is responsible for about 60 percent of the air pollution through out the United States. In some cities, like Los Angeles, cars contribute an even higher percentage, 75 to 80 percent. In terms of weight, the automobiles pours about 180 billion pounds of contaminants into the atmosphere per year. These contaminants have been linked to heart disease, respiratory ailments, and cancer.
Fifty three percent of vehicles tested failed either the hydrocarbon or carbon monoxide test or both at an average of 11,000 miles. Eighty three percent of the General Motors 307 cubic inch engine cars tested failed one or both of the tests at an average of 12,320 miles. Seventy five percent of GM’s 327 cubic inch engines failed one or both tests at an average of 15,204 miles. Of four different size ford engines tested, failure rates ranged for both standards from 28 to 64 percent, at mileage averages from 9,000 to 12,000.
Automobile exhaust effects our ozone everyday. Ozone is a colorless gas and the main component of smog, which is by far the most persistent and widespread air quality problem. It threatens the health of the most vulnerable people in the population, including children, the elderly, those with heart and lung disease, and exercising adults. Short term exposure to high levels can add stress to the body by forcing it to work harder in order to breathe. That aggravates existing respiratory and heart ailments and causes shortness of breath. Long term exposure can accelerate the lung’s natural aging process, resulting in lost breathing capacity. It is estimated that up to one person of every five may
View Full Essay
Smog, Gases, Air pollution, Liquid fuels, Industrial gases, Exhaust gas, Vehicle emissions control, Catalytic converter, Internal combustion engine, Carbon monoxide, Ozone, Combustion
More Free Essays Like This