Land pollution is the addition of undesirable matter to the land that damages the terrestrial organisms, reduce the uses of the land by man for agricultural, residential, recreational or other purposes or increase the risk of health hazards to man. Deposal of normally solid or semisolid materials, resulting from human and animal activities, that is useless, unwanted, or hazardous.
Soil pollution usually results from different human activities, like waste dumping, use of agrochemicals, mining operations and urbanization.
1. Waste dumps: Land gets polluted by dumping of industrial waste, municipal waste, and medical or hospital waste. Industrial solid wastes and sludge are the major sources of soil pollution by toxic organic and inorganic chemical compounds and heavy metals. The fallout from industrial emissions, for example, the fly ash emitted by thermal power plants, can pollute surrounding land. We must keep in mind that the particulates of the industrial emission from the tall chimneys always come back to the earth's surface sooner or later. Radioactive wastes from nuclear testing laboratories and nuclear power plants and the radioactive fallout from nuclear explosions also contaminate the soil. Radioactive materials thrive in the soil from long periods because they usually have a long half-life. Strontium-90, for example, has a half-life of 28 years, and half-life of cesium -137 is 30 years.
2. Municipal wastes: Municipal wastes mainly include domestic and kitchen wastes, market wastes, hospital wastes, livestock and poultry wastes, slaughterhouse wastes, wastes metals, and glass and ceramic wastes, etc. Non-biodegradable materials like used polyethylene carry bags, waste plastic sheets, pet-bottles, etc, persist in soil for long periods. Hospital wastes contain organic materials, chemicals, metal needles, plastic and glass bottles, vials, etc. Dumping of domestic sewage and hospital organic wastes contaminate the environment with a variety of pathogens that can seriously affect human health.
3. Agrochemicals: Pesticides and weedicides are being increasingly applied to control pests and weeds in agricultural systems. Excess inorganic fertilizers and biocide residues are contaminating the soil as well as surface and groundwater resources. Inorganic nutrients, like phosphate and nitrate are washed out to aquatic ecosystems and accelerate eutrophication there. Nitrate can also pollute drinking water. Inorganic fertilizers and pesticides residues change the chemical properties of soil and can adversely affect soil organisms.
4. Mining operations: Opencast mining (a process where the surface of the earth is dug open to bring out the underground mineral deposits) completely devastates the topsoil and contaminates the area with toxic metals and chemicals.
Control measures for soil pollution and land degradation
involve safer land use, planned urbanization, controlled developmental
activities, safe disposal and management of solid wastes from industries and
human habitations. Management of solid wastes involves:
(i) collection and categorization of wastes.
(ii) recovery of resources like scrap metals, plastics, etc, for recycling and reuse.
(iii) safe disposal with minimum environmental hazards.
Sewage sludge and industrial solid wastes are used as landfills. Toxic chemicals and hazardous metal-containing wastes are used as bedding material for road construction. Fly ash is also used for similar purposes. Fly ash bricks are also being used for building constructions. Other notable methods to get rid of the solid wastes are incineration (burning in presence of oxygen) and pyrolysis (combustion in the absence of oxygen). Municipal solid wastes containing biodegradable organic wastes can be transformed into organic manure for agriculture.
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