Components of Environment

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1.1 CLASSIFICATION OF ENVIRONMENT The term Environment can be broadly defined as one’s surroundings. To be more specific we can say that it is the physical and biological habitat that surrounds us, which can be felt by our physical faculties (seen, heard, touched, smelled and tasted.) The two major classifications of environment are : (A) (B) Physical Environment: External physical factors like Air, Water, and Land etc. This is also called the Abiotic Environment. Living Environment: All living organisms around us viz. plants, animals, and microorganisms. This is also called the Biotic Environment. Lithosphere Hydrosphere Atmosphere Biosphere.

Earth’s environment can be further subdivided into the following four segments: (1) (2) (3) (4)

LITHOSPHERE The earth’s crust consisting of the soil and rocks is the lithosphere. The soil is made up of inorganic and organic matter and water. The main mineral constituents are compounds or mixtures derived from the elements of Si, Ca, K, Al, Fe, Mn, Ti, O etc. (Oxides, Silicates, and Carbonates). The organic constituents are mainly polysaccharides, organo compounds of N, P and S. The organic constituents even though form only around 4% – 6% of the lithosphere, they are responsible for the fertility of the soil and hence its productivity. HYDROSPHERE This comprises all water resources both surface and ground water. The world’s water is found in oceans and seas, lakes and reservoirs, rivers and streams, glaciers and snowcaps in 3



the Polar Regions in addition to ground water below the land areas. The distribution of water among these resources is as under Table 1.1 Table 1.1 Oceans and Seas Glaciers and polar icecaps Fresh water 96–97 % 2–3 % < 1%

The water locked up in the Oceans and Seas are too salty and cannot be used directly for human consumption, domestic, agriculture or Industrial purposes. Only less than 1% of water resources are available for human exploitation. Water is considered to be a common compound with uncommon properties. These uncommon properties (e.g. anomalous expansion of water) are mainly responsible for supporting terrestrial and aquatic life on earth. BIOSPHERE The biosphere is a capsule encircling the earth’s surface wherein all the living things exist. This portion extends from 10000 m below sea level to 6000 m above sea level. Life forms do not exist outside this zone. The biosphere covers parts of other segments of the environment viz. Lithosphere, Hydrosphere and Atmosphere. Life sustaining resources like food, water and oxygen present in the biosphere are being withdrawn and waste products in increasing quantities are being dumped. The biosphere has been absorbing this and assimilating them. However the rate of waste dumping has gone beyond the assimilating capability of the biosphere and signals of this stress is becoming evident. ATMOSPHERE It is the gaseous envelope surrounding the earth and extends upto 500 kms above the earth’s surface. The composition of the atmosphere is given in Table 1.2 Table 1.2 Constituent Nitrogen Oxygen Water vapour Argon Carbon dioxide Trace constituents* Volume % 78.1 20.9 0.1–5 0.9 0.03 Balance

*The trace constituents include Helium, Neon, Krypton, xenon, SO2, NO2, Ammonia, Ozone, and Carbon monoxide etc.

The atmosphere, which is a gaseous cover, protects the earth from cosmic radiations and provides life sustaining Oxygen, the macronutrient Nitrogen and Carbon dioxide needed for photosynthesis. The atmosphere screens the dangerous UV radiations from the sun and allows only radiations in the range of 300 nm – 2500 nm (near UV to near IR) and radio waves. The atmosphere plays a major role in maintaining the heat balance of the earth by absorbing the



re-emitted radiation from the earth. In addition the atmosphere is the medium of carriage of water...
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