Soil pollution is the contamination of the soil that prevents natural growth and balance in the land which is used for cultivation, habitation, or wildlife reserve. It is also called as land pollution. Soil pollution sources include hazardous waste and sewage spills, strip mining, deforestation, household dumping, littering, etc. Soil contamination can lead to poor growth and reduced crop yields, loss of wildlife habitat, water and visual pollution, soil erosion, and desertification.
Causes of Soil Pollution
1. Waste Dumps
- Industrial solid wastes and sludge are the major sources of soil pollution by toxic organic and inorganic chemical compounds and heavy metals.
- The fly-ash emitted by thermal power plants can pollute the surrounding land.
- Radioactive wastes from nuclear testing laboratories, nuclear power plants and the radioactive fall out from nuclear explosions also contaminate the soil. Radioactive materials thrive in the soil for longer periods because they usually have a long half-life. Strontium-90, for example, has a half-life of 28 years, and half-life of caesium-137 is 30 years.
2. Municipal Waste
- Municipal wastes mainly include domestic and kitchen wastes, market wastes, hospital wastes, livestock and poultry wastes, slaughter house wastes, glass and waste metal, etc.
- Non-biodegradable materials like used polythene carry-bags, waste plastic sheets, pet-bottles, etc. are non-bio degradable and persist for a long term in the soil.
- Excess inorganic fertilizers and biocides (pesticides, weedicides) are contaminating the soil as well as surface and ground water.
- Inorganic nutrients, like phosphate and nitrate, are washed out to aquatic ecosystems and accelerate eutrophication.
4. Mining Operations
Open cast mining completely devastates the top soils and contaminates the area with toxic metals and chemicals.
Different Forms of Soil Pollution
1. Soil Erosion
- It refers movement of weathered soil from its origin place to another place.
- Soil erosion is mainly dependent on the interaction of exogenetic forces and resistance force of soil particles.
2. Water logging of soil
- When the soil is permanently covered with water and it is completely saturated, i.e., when its pores are filled with water and there is a complete exclusion of atmospheric air from the pores, then toxic elements get added in the soil because of anaerobic reaction.
- Generally, such type of soils is found in poorly irrigated areas like few tracks of green revolution added in soil (states like Punjab, Haryana, Western Uttar Pradesh, Coastal Andhra Pradesh, etc.)
3. Saline and Alkaline soil
- Saline and alkaline soil are infertile soils which are found in a poorly irrigated area.
- At the time of over-irrigation, salts and nutrients of soil translocate downwards by capillary action. When water dries up, then salts and nutrients come back to the top surface by the same method.
- If this process repeats many times, then finally Na, Mg and Ca get concentrated at the top layer of the soil and lead to the formation of solid hard rock pan.
- If the hard rock pan is made up of Na and Mg, then the infertile soil is called saline. If rock pan made up of Ca then it is known as alkaline. These hard rock pans stop the circulation of nutrients and salts on either side which results in the formation of infertile soil. This infertile soil can be reclaimed by application of Zinc and Gypsum.
- Such soils are found in few patches of Haryana, Punjab, Western Uttar Pradesh, Ganganagar and Hanumangarh districts of Rajasthan, etc.
How to Control Soil Pollution
- The best method of control of soil pollution is phytoremediation. In this method, various types of plants are used to destroy the contaminants in the soil and ground water.
- The control of solid wastes involves:
- Collection and categorization of wastes
- Recovery of resources like scrap metals, plastic etc., for recycling and reuse.
- Safe disposal with minimum environmental hazard.
- 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).