Land/Soil contamination || types of soil pollution || meaning and definition of soil pollution || effects of soil pollution
Meaning and definition of land/Soil Pollution/contamination:
Land and Soil are inseperable and hence, land pollution and soil pollution are said to be one and the same. Pollution of land means "degradation of surface of the earth." In other words, soil degradation is the decline in quality and quantity of soil. Land pollution or Land degradation of land takes place for various reasons--namely unscientific agricultural practices/methods, unplanned use of land by dumping of litter, plastic wastes, industrial and domestic wastes etc. Further, construction works, falling of trees and deforestation, urbanization, growth of slums etc. also contribute a lot for land pollution.
The soil is the heart of life. Any sickness of the soil will inevitably affect the health of man. Destruction of soil, erosion of soil, creation of dust bowls etc. render the land polluted. The major source of land pollution is the massive amount of solid wastes deposited of by use here and there.
Land pollution is mostly due to massive solid waste disposal, industrial waste, garbage, commercial rubbish, paper, tyre or plastic wastes.
Household refuse, industrial waste etc. are land pollutants. The most dangerous is plastic component (plastic bags, plastic papers etc.). Chemicals also create land pollution. The major source of land pollution is urbanization. Agricultural operations, mining operations, felling of trees result in land pollution.
Types/kinds of soil pollution: Soil pollution is of two types:
Negative and Positive.
Negative Pollution includes
(i) overuse of soil
(ii) erosion.
Positive soil pollution is caused by
(i) pesticides, herbicides and fumigants
(ii) chemical fertilizers and
(iii) air pollutants washed down from atmosphere through rain.
Causes or sources of soil pollution:
The following activities lead to soil contamination
1. Agriculture
Now with the increase in population and urbanization and the resulting scarcity of agricultural land, land cannot be left uncultivated for any length of time. The same piece of land is cultivated frequently without giving it time to replenish on its own. Over-cultivation causes the soil to lose its nutrients. Chemical fertilizers are added to increase the fertility of the soil. Pesticides are used to kill the pests that are harmful to the crops.
i) Fertilizers and manures: Excessive use of chemical fertilizers decreases population of useful bacteria and crumbs structure of the soil. It also increases salt content of the soil and reduces productivity of the soil.
The excretory products of humans, livestock and digested sewage sludge used as manure pollute the soil. The innumerable pathogens contained in these wastes contaminate the soil and vegetable crops, and cause serious health hazards for man and domesticated animals. However, biological sources are the minor factors in altering soil composition.
iii) Pesticides: Now-a-days a number of chemicals are used to kill insects (insecticides), fungi (fungicides), algal bloom (algicides), rodents (rodenticides), weeds (weedicides or herbicides) in order to improve agriculture, forestry and horticulture. They are sprayed on the plants in the form of fine mist or powder. Most of the pesticides are broad spectrum and affect all types of life. They are called 'biocides'. Pesticides reduce the population and a number of species of living organisms including micro-organisms and thus affect the structure and fertility of soil. Several pesticides or their degradation products are absorbed by plants, which, in turns, may affect the entire food chain, mand food webs.
2. Industrial wastes:
Power plants produce huge amounts of fly ash, which is one of the major causes of soil pollution in the surrounding area. Other industries like paper and pulp mills, oil refineries, chemical and fertilizer manufacturing, iron and steel plants, plastic and rubber-producing complexes, produce large amounts of solid wastes which are dumped on land. They may contain chemicals, which affect the quality of the soil and the life in it. Industrial waste products may be in gas, liquid or solid form. The most important gases are carbon dioxide (CO), nitrogen dioxide (NO) and sulphur dioxide (SO), Food processing plants produce both liquid and solid wastes. They pose a hazard to the soil through toxic emissions of gases.
Effects of soil pollutions of agricultural activities:
1. There are a number of ways in which agricultural practices can impact soil quality. A large proportion of acidic soils have arisen from indiscriminate use of various fertilizers used as sources of the four major nutrients, namely, nitrogen, phosphor, potassium (K) and sulphur (S). Fertilizer run- off leads to the entrophication of waterways.
2. Agricultural practices produce hazardous pollutants in soil, air and water. Particulates are added by wind erosion of unprotected soil by tillage, by burning of any fuel and residues which are released.
Control of soil pollution:
Soil pollution can be controlled by the following items
i. Proper forest management.
ii. Controlled grazing.
iii. Windbreaks and windshields in areas exposed to wind crosion.
iv. Planting of soil-binding grasses and other perennials along the blanks and slopes prone to rapid erosion.
v. Transfer stations should be constructed at various points in cities for bulk transfer of refuse to discharge sites.
vi. Pneumatic pipes should be laid for collecting and disposing wastes. 15. Animal refuse and agricultural wastes can be utilized for production of biogas.
vii. Polluted soil is often dug up and slipped to landfills or hazardous waste sites instead of being cleared. 17. Certain plants concentrate specific elements (for example, loco weed concentrates selenium from the soil). Over a time, the soil becomes depleted of the element. Each year the plants can be harvested and disposed of or sometimes the element can be extracted for use.
viii. Dilution is one way of removing pollutants from the soil. It involves running large quantities of water through the soil to leach out the pollutants. This works only if the soil has good drainage properties. This method requires lots of water.
viii. In vapor extraction, air is injected into the soil to remove organic compounds that evaporate quickly. Bioremediation cleans up the seducing bacteria and other micro-organisms. Phytoremediation uses plants, whose roots absorb pollutants and store them in their stems and leaves.
ix. In the long run it is better for us to adopt sustainable farming practices to prevent the degradation of soil.
x. Use of fertilizer should be highly judicious.
xi. Afforestation and reforestation.
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