Environmental Segments Definition & Explanations
Following are the 4 Environmental Segments:
The lithosphere is the earth’s crust, which is made up of soil and rocks. Inorganic, organic, and water make up the soil, which is the most important constituent of the lithosphere. Compounds or mixes generated from the elements Si, Ca, K, Al, Fe, Mn, Ti, O, and others make up the major mineral ingredients. (oxides, silicates, and carbonates). The organic constituents are mainly polysaccharides, organic compounds of N, P, and S, sugar, and humic materials. 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. The clay minerals and humus supply essential trace metals to the plants due to their high cation exchange capacity.
This comprises all surface and ground-water resources such as seas, oceans, lakes, streams, glaciers, polar ice caps, and the water locked in rock cervices and minerals below earth crust. The distribution of water among these resources are as under:
- Oceans and seas 96-97%
- Glaciers and polar ice caps 2-3 %
- Freshwater <1%
The water locked up in the oceans and seas is 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 due to hydrogen bonding. Without hydrogen bonding water would have boiled at -100’C making life impossible on the earth. Because of Hydrogen bonding, water is a liquid at room temperature, with m.p. of 0°C and b.p. of 100oC at atmospheric pressure. These uncommon properties are mainly responsible for supporting terrestrial and aquatic life on earth.
The biosphere is the region encircling the earth’s surface where life exists. 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 all life forms and their interaction with 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 Life-sustaining resources like food, water, and oxygen present in the biosphere are being withdrawn and waste products in increasing quantities are being dumped.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 are becoming evident.
The atmosphere comprises a mixture of gases (e.g., N2, O2, CO2, Ar, etc), which acts as a protective blanket of gaseous surrounding the earth, that maintains life on the earth. It protects from hostile outer space environment and extends up to 500 km above the earth’s surface. A constant exchange of matter takes place between the atmosphere, biosphere, and hydrosphere. Their relative weights are of the order:
- Biosphere 1
- Atmosphere 300
- Hydrosphere 69,100.
The atmospheric temperature, pressure, and density vary considerably with altitude. The atmosphere protects the earth from cosmic radiation and a major portion of harmful electromagnetic radiation from the sun. The. atmosphere screens the tissue-damaging ultraviolet radiation below 300 nm from the sun and allows only radiations in the range of 300-2500 nm (near UV to near IR) and radio waves. It provides life-sustaining oxygen, the macronutrient nitrogen, and carbon dioxide needed for photosynthesis.
The atmosphere plays a major role in maintaining the heat balance of the earth by absorbing IR radiation from the sun and re-emitting it from the earth in the form of heat. In addition, the atmosphere is the medium of carriage of water from the oceans to the land in the hydrological cycle.