“Soil pollution can be defined as the introduction of substances, biological organisms, or energy into the soil that will lead to a change in the quality of soil so that plant growth and animal health is adversely affected”
Causes of Soil / Land Pollution:
Soil pollution is caused due to direct and indirect sources. The direct sources harm the soil much more than the indirect sources. Examples of direct causes are poor management of solid and liquid domestic/industrial/agricultural waste, water logging, soil erosion, salination, disposal of medical wastes etc. Examples of indirect causes are acid rain and disposal of radioactive substances.
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The main reasons of soil pollution are briefly described below:
(i) Pesticides:
Pesticides are the chemicals which are used by farmers to protect their crops. Large amounts of pesticide in soil interfere with the soil metabolic process. Pesticides kill many non-targeted beneficial soil organisms such as earthworms. Thus, the soil becomes infertile.
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Organo-chlorides (like Dichloro Diphenyl Trichloroethane, DDT) are second generation pesticides. They are non-biodegradable substances. They accumulate and magnify in the food chain and interfere with the calcium metabolism of birds. As a consequence, birds lay fragile, thin-shelled eggs. High concentration of pesticides gets accumulated in fatty tissues of prey organisms. When predators eat these prey organisms, they also get killed.
Thus, pesticides lead to poisoning of the ecosystem.
(ii) Faulty agricultural practices:
(a) Unskilled irrigation:
Water logging may occur when the drainage system of the agricultural field is not maintained scientifically. Water logging closes the passage of air to the soil, stops the growth of soil organisms and makes the soil barren.
(b) Shifting cultivation:
In it, the forest is burnt to use the land for cultivation. However, this practice exposes the soil for soil erosion.
(c) Injudicious use of chemical fertilizers:
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Use of inorganic fertilizers increases the nutrient contamination. The microbes of the soil reduce the nitrogen to nitrite ions which enter the animal body through food, or water. It is directly absorbed in the blood stream and oxidizes the oxyhaemoglobin (the 02 carrier) to methemoglobin. The later cannot carry oxygen any more so ultimately animal dies.
(iii) Solid wastes from homes and industries:
Chemical, petroleum, and metal-related industries, dry cleaners and gas stations produce hazardous waste such as oils, battery metals and organic solvents. This hazardous waste contaminates soil and water resources.
(iv) Acid rain:
It converts neutral soil to acidic one.
Effects of Soil Pollution:
The harmful effects of soil pollution are briefly described below:
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(i) Reduction in the fertility of soil.
(ii) Obstruction in the public passage (road, railway lanes etc.) by solid waste
(iii) Contamination of underground and surface drinking water.
(iv) Fluorosis occurs as a result of consumption of fluoride containing maize, jawar crops. The fluoride is absorbed by the crops from the fluoride contaminated soil.
(v) Emission of toxic gases (from dumped solid wastes on land) is detrimental to health.
(vi) The unpleasant smell and spread of insects cause inconvenience to people.
(vii) Poisoning of the ecosystem take place by soil pollution.
(viii) Soil erosion occurs due to shifting cultivation.
Control of Soil Pollution:
The land pollution can be controlled by following methods:
(i) Planned afforestation helps in preventing soil erosion.
(ii) Use of biofertilizers and natural pesticides help in minimizing usage of chemical fertilizers and pesticides.
(iii) The principles of three Rs, namely, Recycle, Reuse and Reduce help in minimizing generation of solid waste.
(iv) Formulation and effective implementation of stringent pollution control legislation also helps in controlling soil pollution.
(v) Proper disposal methods must be employed. For example, composting of biodegradable solids and incineration of non-biodegradable solids should be done.
(vi) Proper treatment of liquid wastes from industries and mines must be done.
(vii) Faulty sanitation practices must be improved.
(viii) Polluted soil can be treated by bioremediation. It uses microorganisms (yeast, fungi or bacteria) to breakdown, or degrades hazardous substances into less toxic or nontoxic substances (such as CO2 and H2O).