31 October 2020

Environmental Pollution: Basic Concepts, Sources and Nature


Read this article to learn about the basic concepts, sources and nature of environmental pollution.

Environment may be consider as our surroundings which includes everything around us, i.e. the non-living (abiotic) and living (biotic) environment.

The abiotic environment consists of air, water and soil, while the biotic environment includes all the living organisms (plants, animals, microorganisms) that we regularly come in contact.

Environment – Basic Concepts:

The environment is composed of four basic components:


i. Atmosphere

ii. Hydrosphere

iii. Lithosphere


iii. Biosphere.

There is a continuous interaction among the various components of the environment (Fig. 54.1). And ultimately, it is the biosphere that gets influenced by the other components.

The four components of the environment are briefly described.


The atmosphere consists of a blanket of gases, suspended liquids and solids that envelope the earth. The atmosphere is basically derived from the earth itself by various chemical and biochemical reactions. The major components of the atmosphere include the gases nitrogen, oxygen, argon, carbon dioxide, water vapour and suspended particulates (dust, soot).

The composition of the atmosphere depends on time and space, and is highly variable. A liter of air weights around 1.3 g. The atmosphere is vertically divided into four I ayes — troposphere, stratosphere, mesosphere, and thermosphere. This division is mainly based on the increase in the temperature.


The hydrosphere primarily consists of the water on the earth’s surface. Thus, the hydrosphere includes oceans, seas, rivers, streams, lakes, reservoirs and polar ice caps. Water is the most abundant substance on the earth’s surface, which may be present as ice, liquid and vapour. Approximately, 71% of the earth’s surface is covered with water, mainly in the form of oceans.

It is estimated that about 97% of the total earth’s water is in the oceans and inland seas with high salt content. And this water is not useful for human consumption. Around 2% of the water is present in the glaciers and ice caps.

The actual water available for human consumption is around 1% of the total earth’s water. This includes the ground water, water from lakes and rivers and soil moisture. Humans uses water in the homes, industries, agriculture and recreation. There is a continuous decrease in the consumable global water. Therefore, there is a need for precious use of water, and its conservation.



The outer boundary layer of the solid earth on which the continents and the ocean basins rest constitutes the lithosphere. In a broad sense, lithosphere includes the land mass and the ocean floor. However, in a general usage, the term lithosphere refers to the land surface which is approximately 3/10th of the total surface of the earth.

From the biological point of view, the soil is the most important part of the lithosphere because it contains the organic matter and supports growth of plants and microorganisms. Lithosphere is involved in the production of food for humans and animals, besides the decomposition of organic wastes.


The biosphere comprises of all the zones on earth in which life is present. Biosphere is spread over the lower part of the atmosphere, the top of the lithosphere and the entire hydrosphere. In other words, the broad spectrum of bio resources of the earth, supporting life constitutes the biosphere.

It is estimated that the biosphere contains more than 3.5 lakh species of plants (including algae, fungi, mosses and higher plants) and more than 110 lakh species of animals (unicellular, multicellular and higher animals). The biosphere provides the essential requisites (water, light, heat, air, food, space etc.) for the existence of life.


The biosphere is very vast, and for the sake of understanding, it is divided into smaller units namely ecosystems. An ecosystem may be considered as the smallest unit of biosphere that possesses the requisite characteristics to sustain life e.g., ponds, seas, deserts, cities.

Environmental Pollution — Sources and Nature:

Man lives in two worlds—a natural world of the native environment and a built-world created by himself. The built-world, an outcome of the advances made in the science and technology, is associated with environmental pollution. Environmental pollution is a global phenomenon, and therefore a matter of concern for everyone.

Pollution broadly refers to the presence of undesirable substances in the environment which are harmful to man and other organisms. The presence of unwanted substances in the environment may occur due to human activity discharging byproducts, a wide spectrum of waste products and several harmful secondary products

Sources of Pollution:

As already stated, environmental pollution is mostly due to direct or indirect human activities, arising out of the built-world created by him.


There are six major sources of environmental pollution:

1. Industrial sources

2. Agricultural sources

3. Biogenic sources


4. Anthropogenic sources

5. Unnatural sources

6. Extra-terrestrial sources.


The relative importance of each one of these sources depends on the site-specific situation. For instance in cities, anthropogenic sources are the major contributors while in rural areas, agricultural sources significantly add to pollution.

Types of Pollution:

The environmental pollution may be categorized into six major groups:

1. Air/atmosphere pollution

2. Water pollution

3. Land/soil pollution

4. Noise pollution

5. Thermal pollution

6. Radioactive pollution.

Nature of Pollutants:

The pollutants that occur in the environment may be chemical, biological and physical in their nature.

Chemical pollutants:

Gaseous pollutants (sulfur dioxide, nitrogen dioxide), toxic metals, pesticides, herbicides, hydrocarbons, toxins, acidic substances, carcinogens.

Biological pollutants:

Pathogenic organisms, products of biological origin.

Physical pollutants:

Heat (thermal), sound, odours, radiation and radioactive substances.


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