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Pollution is the addition of unwanted materials or pollutants into the environment.

Pollutant is any substance that does not belong in the natural system and disrupts the natural balance.

Type of Environmental pollution

(a)   Air pollution (atmospheric pollution)

(b)   Water pollution (hydrosphere pollution)

(c)   Land (soil) pollution

(d)   Noise pollution

(e)  Thermal pollution


This is a form of environmental pollution caused by the release of gaseous materials and dust particles in the atmosphere.  The main pollutants found in the air we breathe include, particulate matter, lead, ground-level ozone, heavy metals, sulphur dioxide, benzene, carbon monoxide and nitrogen dioxide

Causes of Air Pollution

Man made causes:

(i)  Clearing (deforestation) and burning of vegetation.  This releases carbon dioxide in the atmosphere and dust particles which may be carried by wind on bare land.

(ii)   Burning of fuels:  This releases green house gases in the atmosphere.  Fuels are burnt in cars, power stations and industries.

(iii)   Construction activities, like road, building, etc construction, can add dust particles in the atmosphere.

(iv)   Automobile exhausts.  Car, trains, etc burns fuels as they move his releases pollutant gases in the atmosphere.

(v)   Smokes from industries also pollute the atmosphere.

(vi)  Agriculture activities.  The use of pesticide/insecticides pollutes the air.

(vii)  Mining activities

Natural causes:

(a)   Volcanic eruptions – release smoke and dust particles in the atmosphere

(b)  Wind storms – carry land particles into the air

(c)   Temperature inversion – the increase in temperature in the stratosphere causes high altitude particles to sink to the troposphere


Water Pollution is the degradation of water quality in a manner that disrupts/prevents its intended or original use.

Surface Water or Ground water may be polluted

Causes of water pollution

(i)    Disposal of untreated sewage (industrial or hospital, etc) into the water bodies.

(ii)    Wind may introduce dust particles into water from the land.

(iii)   Agriculture activities near water bodies.  Chemical used during farming may be taken to the water bodies by the rain water.

(iv)   Oil spilt.  The leakage of oil in under water oil pipe, leakage from boats, ships, etc pollutes the water.

(v)   Fishing by using chemicals (dynamite fishing).

(vi)   Volcanic activities along water bodies.

(vii)   Quarrying along the coast.


Soil pollution is defined as the build – up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents which have adverse effects on plant growth and animal health.

A soil pollutant is any factor which deteriorates the quality, texture and mineral content of the soil or which disturbs the biological balance of the organisms in the soil.

Causes of soil pollution

(a)              Chemical from industries

(b)              Acid rain – this increase soil acidity

(c)              Farming activities which make use of insecticides/pesticides

(d)   Mining activities – increase rock sediment into the soil.


Noise pollution is any disorganized loud sound.

Causes of noise pollution

(a)              Noise from factories and workshops

(b)              Thunderstorm explosion of bombs

(c)              Low level flying aircraft

(d)              Radio on large volumes

(e)              Slamming of doors


Thermal Pollution is a form of environmental pollution caused by the release of waste heat into water or air

Causes of Thermal Pollution

(a)              i. Hot gases released by industries and motor vehicles warm the environment.

ii. Hot wasteful liquid from industries pumped to a river, lake, or other waterway

Effects of thermal pollution

(a)  Heat introduced into water can make the water so hot that no living thing can survive in it

(b)  Hot gases introduced in the atmosphere leads to green house effects.

Solutions of thermal pollution

(a)One is a cooling pond into which heated waste water is released before it enters a natural waterway.  The cooling pond permits evaporation of some water, carrying heat into the air and thus releasing cooler water into the waterway

(b)The cooling tower method – either wet or dry – which also transfers heat to the air.  In both types, heated water is introduced into a tower through which air is blown, and some heat is passed to the air.


Particulate matter (aerosol) is the general term used for a mixture of fine solid particles and liquid droplets found in the air.

Haze aerosol is frequently encountered in optical studies and includes any airborne particles that affect visibility.

Classification of Particulate

Particulates matter are classified in accordance with its formation mechanisms

(i) Primary particles     (ii) Secondary particles

Primary particles are directly emitted into the atmosphere from their sources while secondary particles are formed after chemical transformation of their gaseous precursors. Chemical reactions transform primary pollutants (emitted by the sources) to secondary pollutants that are formed within the atmosphere.  Ozone, sulfate aerosols, nitrates, are examples of secondary pollutants.

Particulate matters in the atmosphere are categorized as:

(i)  Minerals, 72 – 91%, e.g. soil particles, hematite, mica, and talc;

(ii) Combustion products, 1 – 10%, e.g. coal and oil soot, fly ash, burned paper.

(iii) Biological materials 2 – 10% e.g. pollen, spores, starch, plant tissues and diatoms

(iv) Miscellaneous matter, trace – 8% e.g. salt, rubber, iron/steel, paint pigment and humus

Dust refers to a relatively course range of solid particles (diameter, d >1pm), produced by disintegration of minerals or from re-suspension by wind when sun blasting of soil particles may often causes comminuting.

Smokes and fumes are fine particles formed from the gas phase by condensation.  In the case of fume the particles are generally from 0.01 – 1 pm diameter, and are often observed as agglomerates of smaller particles.  Suspended particulate matter < 15 pm and diameter is usually defined as smoke.

Mists and fogs are liquid droplets Mists (d > 40 pm) and fogs (d = 5 – 40 pm).

Advantages of particulate matter in the atmosphere

Aerosols acts as nuclei were water vapour collects during the formation of water droplets through condensation.

Disadvantages of particulate matter in the atmosphere

(a)  Cause global warming

(b)  Can block the atmosphere (impair visibility)

(c)  Once deposited on leaves they block stomata and hence no photosynthesis for plant

(d)  Changing the timing and location of traditional rainfall patterns

(e)  Can lead to development of heart and lung diseases.


The transport of pollutants by the wind

The three transport processes that influence the regional dispersion are;

(a)  Wind speed (shear)

(b)  Directional veer (change in direction fo wind), and

(c)  Eddy motion (eddy diffusion).

Wind shear:  The vertical gradient of wind speed (i.e. wind shear is responsible for lagging of low elevation pollutants behind those in the upper layers.

Directional veer:  The directional veer with height causes lateral displacement of a vertically uniform puff.

The eddy motion is the vertical transport of pollutants from region of high concentration to low concentration.  Eddy motions are due to random vertical and horizontal fluctuations caused by thermal and mechanical turbulence.

Both the transport speed and direction for an air parcel vary from day to day.

Stratosphere – troposphere interchange

Temperature inversion at the tropopause causes an interchange of particulate matters between Stratospheres – troposphere boundary.


Atmospheric pollution results into a reduction in visual range in the atmosphere.  The reduction is visual range caused by an increase in airborne particles that affects light scattering and attenuation involves both primary and secondary aerosols, and may be experienced in rural as well as urban area.


Increases in particulate matter in the atmosphere may:

(a)  affect cloud droplet formation and precipitation,

(b)  Reduce the amount of solar radiation that reaches the ground

(c)  Reduce the cooling of the surface layer of the earth at night and influence the global albedo.

However, controversy still remains as to whether the presence of particulate material exerts a net warming or cooling effect to enhance or offset the global warming predicted from increases in CO2 and chlorofluoro methanes in the atmosphere.  In addition, considerable changes in global and surface albedo have been caused by deforestation, salinization, and desertification.

Global warming is the increase of the average temperatures near or on the surface of the earth as a result of greenhouse effect.


Global warming is the increase of the average temperatures near or on the surface of the earth as a result of greenhouse effect.

Greenhouse effect

Greenhouse effect is the process in which the emission of radiation by the atmosphere warms the earth’s surface.

Greenhouse gases include carbon dioxide, methane, chlorofluorocarbons and dinitrogen oxide.

When heat from the sun reaches the earth’s surface in form of sunlight, some of it is absorbed by the earth.  The rest is radiated back to the atmosphere at a long wavelength than the incoming sunlight.  Some of these longer wavelengths are absorbed by the greenhouse gases in the atmosphere before they are lost out of space.  The greenhouse gases reflect the heat back to the earth and warm the environment.

Sources of greenhouse gases in the atmosphere

(a)  Carbon dioxide is added in the atmosphere by:

(i) Clearing and burning of vegetation

(ii) Burning of fossil fuels

(b)  Methane is added in the atmosphere by:

(i) Agricultural activities;

(ii) The mining of coal and oil

(c)  Dinitrogen oxide is added in the atmosphere by:

(i)  Combustion of fossil fuels in vehicles and power station

(ii)  Use of nitrogenous fertilizer, and

(iii)  The burning of vegetation and animal waste

(d)  Sources of chlorofluorocarbon include fridge, air conditioners and aerosols.

Effects of Global Warming

(a)   Increase in the temperature of the oceans,

(b)  Rise in sea levels,

(c)   Change in world’s climatic patterns,

(d)  Acidification of the oceans,

(e)   Extreme weather events like flood, droughts, heat waves, hurricanes and tornadoes

(f)    Higher or lower agriculture yields,

(g)   Melting of Arctic ice and snow caps.  This causes landslides, flash floods and glacial lake overflow,

(h)  Extinction of some animals and plant species,

(i)    Increase in the range of disease vectors (organisms that transmit disease).

Solution to Global Warming

(a)   Use of cleaner alternative sources of energy such as solar and wind,

(b)  Put in place energy conservation measures to reduce the use of fossil fuel,

(c)   Planting trees that would absorb carbon dioxide

(a)   Use of cleaner alternative sources of energy such as solar and wind,


Nuclear wastes are the chemical products (solid, liquid and or gases) of nuclear reactions in the nuclear reactor.

Categories of radioactive waste

For the purpose of disposal, radioactive waste is divided into the following categories:

(a)     High – level waste (HLW):  spent fuel (SF) not destined for reprocessing; vitrified fission product solutions from reprocessing of spent fuel.

(b)    Alpha – toxic waste (STW):  waste with a content of alpha – emitters exceeding a value of 20,000 Becquerel’s per gram of conditioned waste.

(c)     Low – and intermediate – level (L/ILW): all other radioactive waste.

Nuclear Waste Disposal

(a)      Deep geological repository:  for spent fuel and vitrified fission product solution product solutions from reprocessing.  The products are buried deep into the earth.

(b)     Recycling of the nuclear waste.

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