Natural Resources

Tutormate > CBSE Syllabus-Class 9th Biology > Natural Resources

6 Soil Pollution

  • Soil is a mixture of fine particles that cover the outer layer of the earth.
  • It is the abiotic component of an ecosystem.
  • The soil is one of the factors that decide the types and diversity of living things in a habitat.
  • Humus is the decayed living organisms present in soil.
  • Role of Humus in Soil:
    • Decides the quality of the soil
    • Decides soil structure more porous and allows water and air to penetrate deep underground.
    • Gives nutrients to plants
    • Decides the biodiversity of that that area
  • The topmost layer of the soil that contains humus and living organisms in addition to the soil particles is called the topsoil.

Mineral riches in the soil:

  • The biosphere supports life on the earth.
  • It consists of three sub-zones, namely lithosphere (rock, outermost layer), hydrosphere (water) and atmosphere (air).
  • The soil forms the lithosphere or the crust or the outermost layer, of the earth.
  • This layer is rich in minerals required by living organisms.
  • Soil is a mixture of minerals and other matters, similar to the mixture of gases in air.
  • This topmost layer is called topsoil, depending on which, the biodiversity of a region also varies.
  • Soil is composed of dead and decayed matter, microorganisms and other minerals which are useful for living organisms, called humus which is a crucial factor that decides the fertility, texture and other characteristics of the soil.
  • The soil is divided into different types based on the soil particle size, humus content and microorganisms present.
  • The richness of minerals in a type of soil depends on the parent rock it was formed from.
  • Water and the wind take away the minerals and other contents of the soil.
  • Soil is vital for plants to survive.
  • The minerals and nutrients present, humus content, consistency, etc. are some important factors to be considered for cultivation.
  • The top layer of soil contains minerals, humus, microorganisms and other particles.

Formation of soil:

  • Soil is formed from huge rocks and minerals that start to dissolve and break down over thousands and millions of years.
  • Fine particles of soil are formed when rocks, called parent rocks undergo the process called weathering.
  • Weathering involves a series of events under the influence of various factors including physical, chemical and biological processes.
  • Soil formation is influenced by the following factors:
    • The Sun: The rocks on exposure of sun heats up and the rocks cool down and contract at night. This results in the formation of cracks which break up rock into smaller pieces.
    • The Water: Water helps in the formation of soil in two ways:
      • Water gets into the cracks of the rocks formed due to sun. The water in turn freezes and widens the crack.
      • Fast flowing water wears off the hard rocks after a period of time. Fast flowing water carries big and small particles of rock downstream. Then soil then get deposited.
    • The Wind: Similar to water, wind rubs against rocks and wears them down, strong winds also erode rocks down. The wind also carries sand from one place to the other like water does.
    • The Living organisms: The plants, algae, lichens that grow on the surface of rocks Releases substances powder down the rock surface to form a thin layer of soil.

Soil Pollution:

  • Soil is the backbone of agriculture.
  • Farmers started to use fertilizers and other chemicals for higher yields which spoiled the fertility of the soil, by killing micro- and micro-organisms in the soil.
  • The nutrient level in the soil has decreased and has raised the number of barren lands.
  • Deforestations caused soil erosion and soil got exposed to natural disasters.
  • Replenishment of nutrients in the soil by natural methods and organic farming are few solutions for recovering soil fertility
  • The contamination of soil due by harmful substances is called soil pollution.
  • Polluted soil becomes unfit for growing crops and plants and is usually accompanied by water pollution.
  • Water and soil pollution usually occur together as polluted water seeps into soil and contaminates it.
  • Pollutants can also leach out from soil into water bodies when it rains.
  • The most common pollutants are heavy metals like lead and mercury, pesticide compounds, salt and mineral ores.
  • The major causes of soil pollution are over irrigation, pesticides, sewage and garbage dumping, deforestation and mining.

Soil Erosion:

Soil Erosion is the removal and transportation of the top layer of soil from its original position to another place, under the effect of strong winds and fast running rainwater.
Causes of Soil Erosion
Soil erosion is caused by: Strong winds, heavy rains, improper farming and suspended cultivation, human actions, dust storms, frequent floods, deforestation, overgrazing, urbanization, industrialization.
Effects of Soil Erosion
The following are the effects of soil erosion:

  • Loss of fertility and desertification.
  • Landslides in hilly areas
  • Flash floods
  • Famines
  • Silting of water reservoirs

Prevention of Soil Erosion:

Reforestation and afforestation help to prevent soil erosions and loss of other valuable resources. Other methods include:

  • Intensive cropping
  • Sowing grasses and planting xerophytes.
  • Terrace farming (terracing)
  • Contour bunding
  • Conservation tillage
  • Wind breaks.
  • Proper drainage canals around the fields.
  • Making strong embankments along the river banks.

Soil degradation due to extensive farming:

Large amounts of fertilizers and pesticides are used in modern farming practices. This has bad impacts on the soil. The impacts are:

  • Destroys soil structure: Fertilizers and pesticides destroy the soil structure by killing humus that recycle nutrients in the soil.
  • Kills earthworm: It also kills the earthworms which are helpful in making the rich humus.
  • Fertile soils become barren: In case oh not following sustainable practices, like removal of useful components (nutrients) from the soil and addition of other substances (fertilizers, pesticides etc.) affects the fertility of soil. Thereby killing of diversity of organisms that live in it. This causes soil pollution.

Causes of soil pollution:

Soil pollution is caused by

  • Solid wastes and chemicals.
  • The slag heaps from mines spoil the beauty of sites of mines pulp and paper mills, sugar mills, oil refineries, power plants, chemicals and fertilizer manufacturing units, iron and steel plants, plastic and rubber producing complexes are some major contribution to soil erosion.
  • Most industrial furnaces and thermal power stations produce fly ash, which is powdery residue of unburnt material, and causes pollution.

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