Soil is the thin layer of organic and inorganic material that coverts the earth’s rocky surface. Several factors contribute to the formation of soil from parent material. This includes the mechanical weathering of rocks due to temperature changes, abrasion, wind, moving water, glaciers, chemical weathering activities and lichens. The surface litter layer consists of freshly- fallen and partially decomposed leaves, twigs, animal waste, fungi and other organic materials are known as ‘topsoil’.
Soil pollution is the introduction of substances, biological organisms or energy into the soil, resulting in a change of the soil quality, which is likely to affect the normal use of the soil or endangering public health and the living organism. Soil pollutants have an adverse effect on the physical, chemical and biological properties of soil and reduce its productivity.
Land is a very valuable but limited resource, as the population increases rapidly. Many highly urbanized cities are faced with acute space problems, as in Kolkata or Mumbai. Besides the limited availability of land, 175 million hectares of land are becoming less productive every year.
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India loses 20 tons of top-soil per hectare in a year due to floods, rainfall and deforestation. 20% to 50% of lands under irrigation can go out of cultivation at this rate because of water logging and salinity.
Causes of Soil Pollution:
i. Indiscriminate discharge and dumping of industrial effluents on land, thus contaminating them.
ii. An increase in the use of pesticides and fertilizers for agriculture increases soil toxicity.
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iii. Open defecation by animals and human beings.
iv. Accumulation of solid waste; this is a major problem in developed countries like India where the garbage and refuse products are not degraded.
v. Radioactive substances from nuclear plants which are released into the soil. These substances when reach to the soil, persist there for a long time and keep on emitting radiation.
vi. Nitrification process where nitrates are leached out from the soil by plants in presence of nitrifying bacteria.
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vii. Acid rain increases the normal pH of soil and converts neutral soil to acidic one.
viii. Soil erosion of causes the loss of top soil, makes the soil less fertile and reduces its water holding capacity, hence productivity. It also contributes to water pollution by clogging lakes, increasing the turbidity of the water and ultimately leads the loss of aquatic life.
ix. Water logging and salinization increases the soluble salts in soil and makes the soil toxic.
Effects of Soil Pollution:
i. Effects human health
ii. Reduces soil productivity
iii. Decomposition of organic matter by microorganism releases unpleasant odour
iv. Contaminates groundwater
v. Radioactive isotopes replace the essential elements of body and causes abnormalities.
Control of Soil Pollution:
i. Effluents should be properly treated before discharging them on/into the soil.
ii. Solid waste should be properly collected and disposed off by appropriate method.
iii. From the waste, recovery of useful products should be done.
iv. Biodegradable organic waste should be used for generation of biogas.
v. Cattle dung should be used for methane generation.
vi. There should be optimum use of fertilizer and pesticides.
vii. By bioremediation. Bioremediation is a treatment process that uses microorganisms (yeast, fungi or bacteria) to break-down or degrade hazardous substances into less toxic or non-toxic substances (carbon dioxide and water).