2. Major sources of air pollution
1. Automotive Engines
2. Electrical power generating stations
3. Industrial and domestic fuel consumption
4. Refuse burning of industrial processing, wastes etc.,
3. Contribution of automobile emission in air
pollution
As the motor vehicle population in India continues to increase at an annual rate of
approximately 15%, air pollution related to vehicular emissions has become the focus
of attention, especially in large cities.
Based on an investigation into vehicle service characteristics, this study used a series of
driving cycle tests of in-use motor vehicles for their emission factors in laboratories,
which indicated that CO and HC emission factors are 5-10 times higher, and NOx 2-5
times higher, than levels in developed countries.
Results show that vehicle emission is concentrated in major cities, such as Delhi, patna,
gwalior, Raipur.
Motor vehicle emissions contribute a significant proportion of pollutants in those
cities, with contribution rates of CO and NOx greater than 80% and 40%, respectively,
in Delhi and Patna
4. Contribution of automobile emission in air
pollution
The transport sector is the major source of air pollution in the metropolitan cities of
India. There are a number of reasons for the increase in vehicular pollution in the
Indian cities.
(i) Increasing volume of traffic.
(ii) Excessive increase in private/ personal vehicles.
(iii) Improper maintenance of vehicles.
(iv) Growing traffic bottlenecks.
(v) Adulterated fuel use.
(vi) No proper development of public transport as an alternative means of mobility.
6. HC Emissions
A class of burned or partially burned fuel, hydrocarbons are toxins.
Hydrocarbons are a major contributor to smog, which can be a major problem in
urban areas.
Regulations governing hydrocarbons vary according to type of engine and jurisdiction;
in some cases, "non-methane hydrocarbons" are regulated, while in other cases, "total
hydrocarbons" are regulated.
Methane is not directly toxic, but is more difficult to break down in fuel vent lines.
7. Formation of HC Emissions
When unburnt fuel is emitted from a combustor, the emission is caused by fuel
"avoiding" the flame zones.
Some regions of the combustion chamber may have a very weak flame, that is,
they have either very fuel-lean or very fuel-rich conditions and consequently
they have a low combustion temperature.
Ignition Delay.
Cold Starting
Improper formation of mixture.
, evaporative losses from fuel system.
These regions will cause intermediate species such as formaldehyde and
alkenes to be emitted.
Sometimes the term "products of incomplete combustion," or PICs, is used to
describe such species.
8. Effects of HC Emissions
Unburned or partially burned hydrocarbons in gaseous form combine with
oxides of nitrogen in the presence of sunlight to form photochemical smog.
UBHC + NOx Photochemical smog
The products of photochemical smog cause watering and burning of the eyes
and affect the respiratory system, especially when the respiratory system is
marginal for other reasons.
Some of the high molecular weight aromatic hydrocarbons have been shown
to be carcinogenic in animals. Some of the unburned hydrocarbons also serve
as particulate matter in atmosphere.
9. Carbon Monoxide Emissions
Carbon monoxide poisoning is the most common type of fatal air poisoning in
many countries.
Carbon monoxide is colorless, odorless and tasteless, but highly toxic.
At concentrations above 1000ppm it is considered immediately dangerous and is
the most immediate health hazard from running engines in a poorly ventilated
space.
10. Formation of CO Emissions
Fuel rich condition.
Flame quenching causes partial burning.
In SI engines about 0.2-0.5% of exhaust gas contain CO>
Poor mixing of air-fuel mixture.
Predominantly occurs during starting and acceleration.
Incomplete combustion.
11. Effects of CO emissions
The hemoglobin the human blood which carries oxygen to various parts of
the body has great affinity towards carbon monoxide than for oxygen.
When a human is exposed to an atmosphere containing carbon monoxide,
the oxygen carrying capacity of the blood is reduced and results in the
formation of carboxy hemoglobin.
More severe headache and chest pain
14. NOx Emissions
NOx is the sum of NO and NO2.
Nitrogen dioxide is an irritant gas, which at high concentrations causes
inflammation of the airways.
When nitrogen is released during fuel combustion it combines with oxygen
atoms to create nitric oxide (NO)
Nitric oxide is not considered to be hazardous to health at typical ambient
concentrations, but nitrogen dioxide can be hazardous.
15. Formation of Nox Emissions
Combustion temperature.
Equivalence ratio.
Duration of combustion.
Location of spark plug.
16. Effects of NOx Emissions.
Like carbon monoxide, oxides of nitrogen also tend to settle on the hemoglobin in
blood.
Their most undesirable effect is their tendency to join with moisture in the lungs to
form dilute nitric acid.
Because the amounts formed are minute and dilute, their effect is very small but
over a long period of time cam be cumulatively undesirable.
when the respiratory problems like acute bronchitis, pulmonary edema and
respiratory failure for other reasons are found.
Another effect is that, the oxides of nitrogen are also one of the essential
components for the formation of photochemical smog.
17. Particulate Matter
Particulate matter comes from hydrocarbons, lead additives and sulphur
dioxide.
If lead is used with the fuel to control combustion almost 70% of the lead
is airborne with the exhaust gasses.
In that 30% of the particulates rapidly settle to the ground while remaining
remains in the atmosphere. Lead is well known toxic compound
Particulates when inhaled or taken along with food leads to respiratory
problems and other infections.
Particulates when settle on the ground they spoil the nature of the object
on which they are settling. Lead, a particulate is a slow poison and
ultimately leads to death.
22. Effect on environment
Invasive species can out compete native species and reduce biodiversity. Invasive
plants can contribute debris and biomolecules (allelopathy) that can alter soil and
chemical compositions of an environment, often reducing native
species competitiveness.
Nitrogen oxides are removed from the air by rain and fertilize land which can
change the species composition of ecosystems.
Smog and haze can reduce the amount of sunlight received by plants to carry
out photosynthesis and leads to the production of tropospheric ozone which
damages plants.
Soil can become infertile and unsuitable for plants. This will affect
other organisms in the food web.
Sulfur dioxide and nitrogen oxides can cause acid rain which lowers the pH value of
soil.
