INTRODUCTION

• Automotive emissions in aggravating the air pollution and various causes of pollutants have been identified and methods to control them have been outlined.

• The three main types of automotive vehicles being used in our country are:– Passenger cars powered by four stroke gasoline engines– Motor cycles scooters and autorickshaws powered mostly

by small two stroke engines,– Large buses and trucks powered mostly by four stroke

diesel engines,

Vehicle emissions control is the study of reducing the motor vehicle emissions—

emissions produced by motor vehicles, especially internal combustion engines. Emissions of many air pollutants have been shown to have variety of negative effects on public health and the natural environment.

Contd…

• Emissions from gasoline powered vehicles are generally classified as:– Exhaust emissions– Crank case emissions– Evaporative emissions

• The amount of pollutants that an automobile emits depends on a number of factors including the design and operation.

• Diesel powered engines create relatively minor pollution problems compared to gasoline powered ones.

• The major problems of diesel engines are smoke and odor.

EXHAUST EMISSIONS

• In general, an exhaust gas is a gas emitted through a combustion process. The exhaust gas is actually a combination of many different gases: N2, CO2, H2O and O2. Though some are harmless, there are few that are harmful and are considered major pollutants. One of the most dangerous of these is CO, carbon monoxide.

CONTROL OF EXHAUST EMISSIONS• Two main approaches to minimize exhaust emissions

are:– Modifications in the engine design and operating variables.– Treatment of exhaust gases after emission from the engine.

• The following modifications may help in cleaner exhaust– Use of leaner idle mixture– Use of leaner possible mixture and maximum spark retard

compatible with good power output and drivability.– Use of minimum valve-over-lap necessary– Pre-treatment of the mixture to improve vaporization and

mixing of fuel with air.• Piston and ring variables

NITROGEN OXIDES IN EXHAUST GAS

• The concentration of NO in exhaust gas is found to depend mainly on the peak temperature and pressure and the supplied air fuel mixture composition.

• Smog is a kind of air pollution, originally named for the mixture of smoke and fog in the air. Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulfur dioxide. In the 1950s a new type of smog, known as Photochemical Smog, was first described.

Effects on human health

Headaches Eyes, nose and throat irritationsImpaired lung function Coughing and wheezing

GLOBAL WARMING AND THE GREENHOUSE EFFECT

Global Warming Greenhouse Effect

Difference Between Global Warming And The Greenhouse Effect

Global warming refers to a rise in the temperature of the surface of the earth.

The Greenhouse Effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions.

A greenhouse gas is any gaseous compound in the atmosphere that is capable of absorbing infrared radiation, thereby trapping and holding heat in the atmosphere. By increasing the heat in the atmosphere, greenhouse gases are responsible for the greenhouse effect, which ultimately leads to global warming.

The presence of four major greenhouse gases, namely • water vapor (H2O), • carbon dioxide (CO2), • methane (CH4) and • nitrous oxide (N2O) in the Earth's atmosphere

keeps the average temperature of 15º C

whereas without the greenhouse effect the average temperature would be a frosty -18º C (0º F).

• Since pre-industrial times atmospheric concentrations of CO2, CH4 and N2O have climbed by over 31%, 151% and 17%, respectively.

• Scientists have confirmed this is primarily due to human activity. Burning coal, oil and gas, and cutting down forests are largely responsible.

Acid Rain

rainfall made so acidic by atmospheric pollution that it

causes environmental harm, chiefly to forests and lakes.

The main cause is the industrial burning of coal and

other fossil fuels, the waste gases from which contain

sulphur and nitrogen oxides which combine with

atmospheric water to form acids.

• Acid rain results when sulphur dioxide (SO2) and

nitrogen oxides (NOx) are emitted into the atmosphere

and transported by wind and air currents. The SO2 and

NOx react with water, oxygen and other chemicals to

form sulfuric and nitric acids. These then mix with

water and other materials before falling to the ground.

The major sources of SO2 and NOX in the atmosphere are:• Burning of fossil fuels to generate electricity. Two

thirds of SO2 and one fourth of NOX in the atmosphere come from electric power generators.

• Vehicles and heavy equipment.• Manufacturing, oil refineries and other industries.

Forms of Acid Deposition

Wet Deposition• Wet deposition is what we most commonly think of as acid

rain. The sulfuric and nitric acids formed in the atmosphere fall to the ground mixed with rain, snow, fog, or hail.

Dry Deposition• Acidic particles and gases can also deposit from the

atmosphere in the absence of moisture as dry deposition. The acidic particles and gases may deposit to surfaces (water bodies, vegetation, buildings) quickly or may react during atmospheric transport to form larger particles that can be harmful to human health.

• The amount of acidity in the atmosphere that deposits to earth through dry deposition depends on the amount of rainfall an area receives. For example, in desert areas the ratio of dry to wet deposition is higher than an area that receives several inches of rain each year.

• Normal rain has a pH of about 5.6; • It is slightly acidic because carbon dioxide

(CO2) dissolves into it forming weak carbonic acid. Acid rain usually has a pH between 4.2 and 4.4.

Ozone Layer DepletionOzone is formed in the stratosphereThe overall amount of ozone in the stratosphere is determined by a balance between photochemical production and recombination.

Ozone is bluish, a very reactive gas, whose molecule is made by three oxygen atoms

Ozone will protect us from UV radiation from the sun.UV radiations can cause skin cancer, genetic mutations and cataracts.

• The ozonosphere is found 15-35 km (9 to 22 miles)

above the surface of the earth.

• The average concentration of ozone in the

atmosphere is around 0.6 parts per million.

• The thickness of the ozone layer differs as per season

and geography. The highest concentrations of ozone

occur at altitudes from 26 to 28 km (16 to 17 miles)

in the tropics and from 12 to 20 km (7 to 12 miles)

towards the poles.