7 Short Questions with Answers for School Students on “Environmental Pollution”

Q. 1. Name different types of pollutions. Define them.

Air pollution may be defined as the presence of one or more contaminants in the atmosphere in such a quantity and of such duration as is or tends to be injurious to human health of welfare, animal or plants or properties or would unreasonable interfere with enjoyment of life and property.

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Water pollution is defined as presence of any foreign substance (organic, inorganic, biological or radiological) in water which tends to degrade the quality so as to constitute a hazard, or impair the usefulness of water.

Soil pollution is the introduction of substances, biological organisms or energy into the soil, resulting in a change of the soil quality, which is likely to affect the normal use of the soil or endangering public health and the living organism.

Marine pollution can be defined as the direct or indirect introduction of substances or energy into the marine environment (including estuarine), causing in harm to living resources, hazards to human health, hindrance to marine activities including fishing and impairment of the quality of sea water.

Thermal pollution can be defined as presence of waste heat in the water which causes undesirable changes in the natural environment.


Q.2. What do you understand by secondary pollutants? Give the reaction for their formation.

Secondary pollutants are pollutants formed by the photochemical reaction of primary pollutants. For example, “Photochemical smog”, is a combination of hydrocarbons and oxides of nitrogen.

HCS + NOx – Photochemical Smog

Q.3. Explain the following terms:


(i) Eutrophication

(ii) Sanilisation

(iii) Biomagnification

(iv) PAN

(v) CFC’s

(vi) MIC

(i) As due to run-off with water the nutrients reaches in the water body and that been rich nutrient and the rate of growth of aquatic plants increases very rapidly and penetration of sunlight to the bottom of the water body in not possible and amount dissolved oxygen decreases that effects aquatic life, this process is known eutrophication.

(ii) Salinisation refers to a buildup of salts in soil, eventually to toxic levels for plan (3,000 – 6,000 ppm salt results in trouble for most cultivated plants.) Salt in soils decreases the osmotic potential of the soil so that plants can’t take up water from it. When soils are salty, the soil has greater concentrations of solute than does the root, so plants can’t get water from soil.

(iii) Biomagnification is the increase in concentration of an element or compound, such as pesticides (DDT) that occurs in a food chain as a consequence of food chain energetic; or lack of or very slow, excretion or degradation of the substance.

(iv) Peroxyacetyl nitrate (PAN) is a secondary pollutants and primarily responsible for damage to plant life and leads to the formation of photochemical smog which results in eye irritation in human being.

(v) Chlorofluorocarbons (CFCs) are ozone depleting substances such as halons (bromo- fluoro-carbons) and methyl bromide. In certain circumstances the chlorine or bromine from these substances can react with ozone to turn it back into oxygen.

(vi) Methyl isocynate (MIC) is a potent toxicant and was released in to the atmosphere in Bhopal on December 3, 1984 at midnight from a pesticide manufacturing plant (Union Carbide factory) due to the alleged functional failure of vent scrubber outlet resulting in the deaths of about 1,00,000 people and severe disability of an additional 1,00,000 of the city’s population.

Q.4. Write short notes on:

(i) Solid waste management practices

(ii) Sources, effects and control measures of noise pollution

Solid Waste Management Practice is supervised handling of waste materials from their source through recovery processes to disposal. The solid waste is non-liquid, non-soluble materials ranging from municipal garbage to industrial wastes that contain complex and sometimes hazardous substances. Solid wastes also include sewage sludge agricultural refuse, demolition wastes, and mining residues.

Noise pollution may come from loudspeakers, factories, and airplanes, moving trains, construction activity or even a radio. Continued exposure of noise results in high levels fatigue, temporary or permanent shift of the hearing threshold of a person (hearing loss or even total loss of hearing), changes in blood circulation, changes in breathing etc. Noise pollution could be controlled by either reducing the noise at the source or preventing its transmission or by protecting the receiver.

Q.5. Mention the causes of Smog.

Causes of Smog:

Some of the main sources of Smog are: gasoline and diesel powered vehicles, factories and utilities, oil-based paints, solvents and cleaners, pesticides, road paving (asphalt) and construction and coal-fired generating stations.

Q.6. What do you understand by threshold limit of hearing?

The minimum sound pressure level that a particular can hear is known as threshold limit of hearing.

Q.7. Differentiate the following:

(a) Natural and man-made sources of pollution (with example)

(b) London smog and Los Angeles smog

(c) Fog and smog

(d) Noise and sound

(e) Primary and secondary air pollutants

(f) BOD and COD

(g) Pyrolysis and composting

(a) Natural sources of pollution are source those emit pollutant naturally like volcanic eruption, forest fires, bio-pollutants etc. while manmade sources are those where pollutants comes in the atmosphere by human activities like burning of fossil fuels, automobiles, plants and industries.

(b) This type of smog is thought to be caused by sulphur dioxide. It is formed by combination of smoke, dust, fog and SO2. Chemical smog is usually formed around some industrial and power plants whereas Lo~ Angeles smog (photochemical smog is associated with adverse meteorological conditions (inversion conditions) when movement is restricted in summers in highly motorised areas.

(c) Fog is special type of thin cloud consisting of microscopically small water droplets which are kept in suspension in the air near the ground surface while smog (smog + fog) is two types- one is found in places having coal as the principal fuel. The other one is photochemical smog.

(d) Sound is mechanical energy from vibrating source. Noise can be defined as an unpleasant and unwanted sound.

(e) Primary pollutants are those which are emitted directly into the atmosphere, like sulphur dioxide, nitric oxides and carbon monoxide while Secondary pollutants are pollutants formed by the photochemical reaction of primary pollutants.

(f) The Biochemical Oxygen Demand (BOD) is a measure of the oxygen required by aerobic micro-organisms to biochemically oxidize the organic matter present in the waste and is expressed in mg/1.

Another quick measure of organic matter present in waste is Chemical Oxygen Demand (COD) and in this case chemical oxidants (potassium dichromate in acidic conditions) are used instead of aerobic micro-organisms for the oxidation of organic matter.

(g) In Pyrolsis, the solid wastes are heated under anerobic conditions, i.e., burning without oxygen. The organic components of the solid wastes split up into gaseous liquid and gaseous fractions (CO, C02, CH4, tar, charred carbon etc.) whereas composting is one of the oldest forms of disposal.

It is the natural process of decomposition of organic waste that yield manure or compost, which is very rich in nutrients. Composting is a biological process in which micro­organisms, mainly fungi and bacteria, convert degradable organic waste into humus like substance.


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