Lecture 7 - The Environmental Impact of Vehicle Emissions.doc

The Environmental Impact of Vehicle Emissions From: Illinois EPA Emissions from an individual car are generally low, relative to the smokestack image many people associate with air pollution; however, in numerous cities across the country, the personal automobile is one of the single greatest sources of air pollution as emissions from millions of vehicles on the road add up. Vehicle emissions are responsible for up to 50 percent of
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  The Environmental Impact of Vehicle EmissionsFrom: Illinois EPA Emissions from an individual car are generally low, relative to the smokestack image many people associate with air pollution; however, in numerous cities across the country, the personal automobile is one of the single greatest sources of air pollution as emissions from millions of vehicles on the road add up. Vehicle emissions are responsible for up to 50 percent of the emissions that form ground-level oone and up to !0 percent of carbon mono ide in ma#or metropolitan areas. $riving a private car is probably a typical citien%s most &polluting& daily activity. 'he power to move a car comes from burning fuel in an engine. (ollution from cars comes from)  by products of this combustion process *e haust+ and,  from evaporation of the fuel itself * Emissions generated ! ra es and tires are not mentioned in this article ut the! are also an important source of emission +asoline and diesel fuels are mi tures of hydrocarbons -- compounds that contain hydrogen and carbon atoms. n a &perfect& engine, o ygen in the air would convert all the hydrogen in the fuel to water and all the carbon in the fuel to carbon dio ide. itrogen in the air would remain unaffected. n reality, the combustion process cannot be &perfect,& and automotive engines emit several types of pollutants. &(erfect& /ombustion) uel *hydrocarbons+ 1 air *o ygen and nitrogen+ 2 carbon dio ide 1 water 1 unaffected nitrogen 'ypical Engine /ombustion) uel 1 air 2 unburned hydrocarbons 1 nitrogen o ides 1 carbon mono ide 1 carbon dio ide 1water E#haust Pollutants$!drocarons %$&':  3ydrocarbon emissions result when fuel molecules in the engine do not burn or burn only partially. 3ydrocarbons react in the presence of nitrogen o ides and sunlight to form ground-level oone, a ma#or component of smog. 4one irritates the eyes, damages the lungs, and aggravates respiratory problems. t is our most widespread and intractable urban air pollution problem.  number of e haust hydrocarbons are also to ic, withthe potential to cause cancer. (itrogen o#ides %()#':  6nder the high pressure and temperature conditions in an engine, nitrogen and o ygen atoms in the air react to form various nitrogen o ides, collectively known as 4 . itrogen o ides, like hydrocarbons, are precursors to the formationof oone. 'hey also contribute to the formation of acid rain. &aron mono#ide %&)':  /arbon mono ide is a product of incomplete combustion and occurs when carbon in the fuel is partially o idied rather than fully o idied to carbon dio ide.  /arbon mono ide reduces the flow of o ygen in the bloodstream and is particularly dangerous to persons with heart disease. &aron dio#ide %&)*':  n recent years, the 6.7. Environmental (rotection gency has started to view carbon dio ide, a product of &perfect& combustion, as a pollution concern. /arbon dio ide does not directly impair human health, but it is a &greenhouse gas& that traps the earth%s heat and contributes to the potential for global warming. Evaporative Emissions 3ydrocarbon pollutants also escape into the air through fuel evaporation. 8ith today%s efficiente haust emission controls and modern gasoline formulations, evaporative losses can account for a ma#ority of the total hydrocarbon pollution from current model cars on hot days when oone levels are highest. Evaporative emissions occur several ways) +iurnal:  asoline evaporation increases as the temperature rises during the day, heating the fuel tank and venting gasoline vapors. ,unning -osses:  'he hot engine and e haust system can vaporie gasoline when the caris running $ot oa :  'he engine remains hot for a period of time after the car is turned off, and gasoline evaporation continues when the car is parked. ,efueling: asoline vapors are always present in fuel tanks. 'hese vapors are forced out when the tank is filled with li9uid fuel. ederal standards dictate how much pollution autos may emit, and automakers decide how to achieve the pollution limits. 'he emission reductions of the :!0%s came about because of fundamental improvements in engine design, plus the addition of charcoal canisters to collect hydrocarbon vapors and e haust gas recirculation valves to reduce nitrogen o ides.'he advent of &first generation& catalytic converters in :!5 significantly reduced hydrocarbon and carbon mono ide emissions. 'he use of catalytic converters provided a huge indirect benefit as well. <ecause lead inactivates the catalyst, :!5 saw the widespread introduction of unleaded gasoline. 'his resulted in dramatic reductions in ambient lead levels and alleviated many serious environmental and human health concerns associated with lead pollution. 'he ne t ma#or milestone in vehicle emission control technology came in :!=0-=:. n responseto tighter standards, manufacturers e9uipped new cars with even more sophisticated emissioncontrol systems. 'hese systems generally include a new catalyst, plus an on board computer and o ygen sensor. 'his e9uipment helps optimie the efficiency of the catalytic converter. Efforts by government and industry since :!0 have greatly reduced typical vehicle emissions.7ince then, however, the number of miles we drive has more than doubled. 'he increase in travel has offset much of the emission control progress. The net result is a modest reduction in each automotive pollutant e#cept lead for which aggregate emissions have dropped ! more than 01 percent. From Wikipedia, the free encyclopedia List the following sources of emissions must be considered:   Life cycle emissions : These are produced in activities associated with the manufacturing, maintenance, and disposal of the automobile and include such items as: 1.anufacturing plant power re!uirements .#olatile solvents utili$ed in the manufacturing process %auto  paint finishes, etc& '.(utgassing of synthetic materials utili$ed to reduce weight and simplify manufacturing ).aintenance re!uirements such as oil and filter changes,  battery replacement, etc. *.+isposal re!uirements including contaminated lubricants, tires, heavy metals, and landfill $eath Effects of Pollution from Vehicle Engines >esearch indicates that appro imately ?,00 premature deaths and thousands of medical emergencies are linked to air pollution in the greater metropolitan /hicago and East 7t. @ouis areas each year. /arbon mono ide and hydrocarbons are the two main e haust gases produced by the combustion process in gasoline powered vehicles. &aron mono#ide   is a colorless, odorless, to ic gas. t is a by-product of incomplete combustion. Aotor vehicles produce more than two-thirds of the man-made carbon mono ide in the atmosphere. /arbon mono ide reduces the volume of o ygen that enters the bloodstream and can slow refle es, cause drowsiness, impair #udgment and vision and even cause death. $!drocarons   are unburned fuel vapors. 8hen hydrocarbons and other pollutants are e posed to sunlight, a chemical reaction occurs that produces ground-level oone *smog+, which is harmful to our health and the environment. Vehicles are responsible for about 50 percent of the emissions that form oone. (itrogen o#ides , like hydrocarbons, are precursors to the formation of oone. 'hey also contribute to the formation of acid rain. 2hat is )3one4 4one is a form of molecular o ygen that consists of three o ygen atoms linked together. 4one in the upper atmosphere *the &oone layer&+ occurs naturally and protects life on earth by filtering out ultraviolet radiation from the sun. 4one at ground level is a no ious pollutant.  t is the ma#or component of smog and presents this country%s most intractable urban air 9uality problem. 4one is a severe irritant. t is responsible for the choking, coughing, and stinging eyes associated with smog. 4one damages lung tissue, aggravates respiratory disease, and makespeople more susceptible to respiratory infections. /hildren are especially vulnerable to oone%sharmful effects, as are adults with e isting disease. Even otherwise healthy individuals may e perience impaired health from breathing oone-polluted air. Elevated oone levels also inhibit plant growth and can cause widespread damage to crops and forests. 4one is not emitted directly. t is formed in the atmosphere through a comple set of chemical reactions involving hydrocarbons, o ides of nitrogen, and sunlight. 'he rate at which the reactions proceed is related to both temperature and intensity of the sunlight. <ecause of this, problematic oone levels occur most fre9uently on hot summer afternoons. 3ydrocarbons and nitrogen o ides come from a great variety of industrial and combustion processes. n typical urban areas, at least half of those pollutants come from cars, buses, trucks, and off highway mobile sources such as construction vehicles and boats. 2h! Aren5t )3one -evels +ropping4 4one levels in many cities have come down with the introduction of lower volatility gasoline and as newer cars with improved emission control systems replaced older models. lthough there has been significant progress since :!0 in reducing emissions per mile traveled, the number of cars on the road -- and the miles they travel -- almost doubled in the same time frame. n the ten years from :!!: to B00:, fuel sold and vehicle miles traveled increased about B5 percent.ncreased sales of sport utility vehicles and trucks also contribute to the problem. 7ales of 76Vs and light trucks have increased B0 percent since :!C. n B00:, 76Vs and trucks overtook cars in sales, and accounted for almost 55 percent of the vehicles sold in B00?. 3owever, these vehicles wonDt have to meet passenger car emissions standards until model year B00. second reason that oone levels remain high is that emission control systems do not always perform as designed over the full useful life of the vehicle. >outine aging and deterioration, poor maintenance, and tampering with emission control devices can all increase vehicle emissions. n fact, a ma#or portion of oone forming hydrocarbons can be attributed to a relatively small number of &super dirty& cars whose emission control systems are not working properly. 6nless we dramatically reduce the amount of pollution vehicles emit in actual use, or drastically cut back on the amount we drive, smog free air will continue to elude us. Fine Particulate Matter  Source: Ontario Minister of the Environment  What is fine particulate matter?  articulate matter is characteri$ed according to si$e - mainly because of the different health effects associated with particles of different diameters. articulate matter is the
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