Class 11 Biology Environmental Pollution Notes

Environmental Pollution

Pollution

Pollution is defined in the source as an unfavourable alteration of the surroundings, wholly or partially, due to by-products of human activities or other causes.

Pollutants

The things or substances which cause pollution are known as pollutants.

Types of Pollutants

1. Based on Decomposability

Biodegradable Pollutants

Pollutants which are degraded or decomposed by microorganisms are called biodegradable pollutants.

Example in the source: organic domestic wastes.

Non-degradable Pollutants

Pollutants which cannot be degraded are called non-degradable pollutants.

Examples: mercuric salts, phenol compounds, DDT, etc.

2. Based on Chemical Complexity / Formation

Primary Pollutants

Air pollutants emitted directly from a source.

Examples in the source: ash emitted from a volcanic eruption, carbon monoxide from motor-vehicle exhaust and sulphur dioxide released from factories.

Secondary Pollutants

Pollutants which are not emitted directly but form when primary pollutants react in the atmosphere.

Examples: ozone, acid rain, etc.

Pollutants → Biodegradable Non-degradable Primary Secondary

A. Air Pollution

The presence of harmful or poisonous substances in the air is known as air pollution.

Sources / Causes of Air Pollution

Emission of a high concentration of CO₂ from burning fuels such as fuel oil, petrol and coal.
Release of excessive smoke into the air.
Formation or release of carbon compounds, sulphur compounds, lead compounds and oxides of nitrogen that contribute to harmful smog, as listed in the source.
Release of SO₂, NO₂ and hydrocarbons from industrial gases.
Motor vehicles produce CO₂, CO, oxides of nitrogen, hydrocarbons and other pollutants.
Emission of cotton-dust particles.
Irrational use of herbicides and insecticides.
Exposure to or release of radioactive elements.
Mixing of dust particles in the air from barren fields, construction sites, moving vehicles and damaged roadsides.

Effects of Air Pollution

1

Health Problems

The source lists allergy, eye problems, throat problems, asthma, heart problems, bronchitis and cancer among health effects.

2

Formation of CFCs / Ozone Damage

The handwritten notes state that the ozone layer is depleted due to excessive air pollution, resulting in greater exposure to harmful ultraviolet rays with carcinogenic and other health effects.

3

Global Warming

The source states that air pollution is responsible for global warming.

4

Acid Rain

Acid rain causes severe damage to crop plants and other organisms or materials.

5

Visibility Problems

Reduced visibility creates problems while driving, may contribute to road accidents and can also create difficulties in aircraft operation.

6

Degradation of Breathing Air

Air pollution lowers the quality of the air available for breathing.

On page 3, the handwritten headings and explanations around “Formation of CFCs,” “ozone layer depletion” and “global warming” are not perfectly aligned. They are organized here without adding outside scientific corrections.

Control of Air Pollution

Industries should be modernized and technologically upgraded so that they emit fewer pollutants.
Vehicles and industries should be regulated through strict laws.
The source recommends controlling pollution-producing substances and processes associated with burning solid wastes.
Afforestation programs should be promoted.
Radioactive elements should be disposed of properly.
People should be made aware through public-awareness campaigns as much as possible.

B. Water Pollution

A deterioration or decrease in the purity and quality of water by any medium is described in the source as water pollution.

Sources / Causes of Water Pollution

Mixing of industrial effluents, radioactive elements, mercury or other heavy metals, fertilizers and pesticides with natural water bodies.
Dissolved gases such as CO₂, H₂S and CH₄, oxides of nitrogen and dissolved salts of calcium, magnesium, sodium, iron, carbonates, bicarbonates and sulphates may contribute to deterioration of water quality.
Suspended and colloidal materials, including bacteria, fungi, protozoans and worms, also deteriorate water quality and act as causes of pollution.

Effects of Water Pollution

It may kill aquatic animals directly due to toxic effects of chemicals.
It disrupts natural food chains and aquatic ecosystems.
The source lists harmful effects on human health such as skin allergy, eye problems, jaundice, dysentery, diarrhoea and typhoid.
Polluted water becomes unsuitable for irrigation, cattle consumption, bathing, cleaning and similar uses.
Excessive growth of algae may reduce available oxygen, causing aquatic animals to die due to lack of oxygen.

Control of Water Pollution

Harmful substances from industrial sectors should not be mixed or drained into river systems, and such discharge should be regulated by law.
Microbial decomposition in industrial wastewater should be properly checked or managed.
Ponds and reservoirs should be cleaned periodically.
Excessive use of pesticides and chemical fertilizers in agricultural land should be discouraged.
Domestic wastes should be disposed of properly.

Methods of Purification of Polluted Water

Natural Ways

Artificial Ways

C. Soil (Land) Pollution

The presence of solid wastes, chemicals and other pollutants in soil is called soil or land pollution.

Sources / Causes of Soil Pollution

Areas surrounding mining and smelting complexes may release metals such as Cd, Zn, Pb, Cu and Ni, which the source describes as phytotoxic even in small quantities.
Industries such as paper mills, oil refineries, power and heating plants, chemical and fertilizer manufacturers, iron and steel plants, plastic plants and rubber-producing plants generate by-products that may be dumped in soil, burnt or emptied into rivers.
Agricultural use of chemical fertilizers, herbicides, insecticides and fungicides contributes to soil or land pollution.
Disposal of household or domestic wastes—such as grocery waste, food scraps and vegetable remains—into soil also causes soil pollution.

Mining & smelting Industrial wastes Agricultural chemicals Domestic wastes

Effects of Soil Pollution

Heavy metals such as Cd, Zn, Pb, Cu and Ni may make plants unsafe for human and animal consumption even when present in small amounts, according to the source.
Soil pollution decreases soil productivity.
Harmful chemicals and pesticides may cause long-term effects on human health.
Pesticides washed into water bodies may create serious hazards for aquatic life.
It degrades soil quality and may make the soil unsuitable for various agricultural practices.

Control of Soil Pollution

Disposable wastes from different sectors should be disposed of in proper places.
Animal solid wastes can be used as biofertilizers or in biogas plants instead of being carelessly discarded.
Radioactive materials should be disposed of by scientific methods.
The use of chemicals such as fertilizers, insecticides and herbicides in soil should be regulated rationally.

D. Pesticides

Pesticides are chemicals synthesized specifically for the purpose of killing unwanted species such as insects, molluscs and some mammals.

The source gives examples of unwanted organisms such as cockroaches, mosquitoes, aphids, termites, snails and rats.

The supplied notes divide pesticides into three main types:

1

Herbicides

Chemicals synthesized especially for killing unwanted plants.

2

Insecticides

Chemicals used to kill insects that damage crops, vegetables, human belongings and other materials.

3

Fungicides

Chemicals used for the eradication or control of fungal problems.