Soil is the uppermost part of the earth crust and is believe to have been formed as a result of decomposition and disintegration of surface rocks due to weathering over a very long period of time. It might have been formed at far of distance but is carried by strong winds rivers to different places.
The prosperity of a nation depends upon the quality of soil as it is the soil which provides nutrients, water and minerals for the growth of the plants. It is, infact, the heart of biosphere.
However, large scale of cutting of trees for human needs due to increase in population, digging of minerals, increasing brick-kilns, poisonous effluent of the industries and dumping of toxic and harmful wastes, increase in the use of automobiles etc. are damaging the quality of the soil and resulting into soil pollution. In India, it is sad to point out that backwardness of our people is an additional factor for soil pollution, e.g using open air lavatories by slum dwellers thereby inviting pig, crows, other vulture and files, throwing of domestic wastes including peeling of vegetables and fruits, plastics, polythene bags etc.
<b>Composition of the Soil :-</b>
1. Mineral matter :- it comprise of mineral particles of different sizes which originate from the rock and are formed by its disintegration. They are present as gravel, coarse sand, fine sand, slit, and clay.
2. Organic matter :- This is present in the soil as a result of fallen trees and mixing their parts such as roots, leaves etc. And also from the remains of dead animals and their excreta. These materials are decomposed by microorganisms present in the soil and convert them into humus. Humus has all those excellent properties which are an urgent need of the plants.
3. Biological system :- It consist of algae, bacteria, protozoa etc. Which help in the decomposition of organic matter present in the soil.
4. Soil water :- The water present in the soil acts as a solvent for various organic and inorganic materials needed for the plants and also act as a transporting agent by carrying nutrients from the soil to different parts of the plant.
5. Soil air :- It is present in the pores of the soil, i.e the space between the soil particles. It contains more of carbondioxide and moisture than oxygen. Out ids needed for soil microorganisms and underground parts of the plants.
The soil containing almost equal amounts of sand, slit and clay alongwith humus and 34% air and 66% water is consider to the best soil for most of the crops. It is called loam soil.
<b> Sources of Soil Pollution :-</b>
1. Industrial Wastes :- It has been estimated that about a 50% of the raw material used by most of the industries becomes waste product which is either thrown into the soil nearby. This industrial waste contain huge amounts of toxic and disastrous chemical many of which are non-biodegradable. Some of the industries responsible for soil pollution are paper mills , pulp mills, sugar mills, chemical industries and petroleum industry etc.
2.Urban Wastes :- Urban wastes consist of soil refuse containing garbage and rubbish material like paper pieces, glass, plastics, used cans, leaves, polythene bags, peeling of vegetables and fruits etc. These wastes emit out poisonous gases, toxic hydrocarbons and pathogenic microbes which cause disease.
3. Agricultural pollutants :- No Doubt, the use of fertilizers, pesticides , soil conditioners , etc. have increase the yield from the crops but they have polluted the soil. Their entry into food chain has adversely affected the health of the human beings and led to a number of diseases. Some of the agricultural pollutants are :-
* Fertilizers
* Pesticides
* Insecticides
* Fungicides
* Soil conditioners
* Farm wastes
4. Radioactive Pollutants :- Dumping of the nuclear wastes from the nuclear power plants into the soil has been one of the greatest source of radioactive pollution of the soil. Nuclear tests produce nuclear dust in the atmosphere which ultimately falls into soil and pollutes it. The use of atomic and hydrogen bomb in the wars produces radioactive nuclides as the by-products.
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