A change or alteration in the natural physical, chemical, and biological properties of soil because of human activities degrades the quality and productivity of the soil. This is known as soil pollution.
Sources of soil pollution
- Discharges from industries such as used chemicals and fly ash are dumped into the ground polluting the soil.
- Municipal wastes, hospital wastes, and market wastes lead to soil pollution.
- Use of chemical fertilizers which contain nitrogen, potassium, and phosphorus results in soil pollution as it contaminates soil with impurities.
- Disposal of biomedical wastes such as hospital wastes and domestic wastes contaminates the soil with pathogens (disease-causing bacteria) which may affect human health. Intestinal parasites cause the most serious soil pollution problems in third-world countries.
- Pesticides and weedicides which are used for controlling pests and weeds on agricultural fields may settle on soil permanently, passing these toxic materials to plants
Types of Soil Pollutants
Various kinds of soil pollutants are
- Organic pollutants: These include human and animal excretion, waste food items, poultry wastes, and wastes from food processing industries.
- Inorganic pollutants: Metallic wastes, chemical fertilizers, detergents, oil, and heavy metals are some inorganic wastes that pollute the soil. As these wastes do not degrade quickly, they decrease the quality and the productivity of the soil.
- Radioactive substances: These are extremely toxic. They have long-lasting effects on the properties of soil.
Effects of Soil Pollution
Soil pollution affects humans and animals through the process of the food chain.
- Industrial effluents and chemical wastes cause pollution of underground water.
- Crops and plants which grow on infected soil absorb the pollutants and then pass them on to animals and humans. This can result in chronic illnesses.
- Nitrogenous fertilizers produce a toxic concentration of nitrate and nitrite in the leaves.
- Soil pollution results in the loss of soil fertility and hence affects its productivity.
Effects of Soil Pollution on Human Health
- Polluted soil may contain pathogens, viruses, and intestinal worms which may enter the human body through the consumption of fruits and vegetables. These bacteria and viruses may cause many types of diseases among humans.
- If humans consume animals that graze on grass and leaves of trees which are grown on soil affected with radioactive elements, it may create several abnormalities in human organs.
- Human and animal excreta also contain pathogens. This may contaminate the soil and crops which may indirectly affect human health.
Prevention of Soil Pollution
In open dumping, wastes are dumped in open spaces located far away from the limits of the city. This kind of waste disposal is not safe and has many limitations. The dumping of different types of wastes makes such dumping grounds as the breeding ground of mosquitoes and flies. The burning of these wastes also pollutes the air. The situation can become worse during rains. Rainwater may carry these wastes to nearby lakes, rivers, or ponds and pollutes them.
Wastes are disposed of away from the city in sanitary landfills. The waste is first spread in layers and then is compacted tightly so that its volume is reduced. The waste is then covered by soil and subjected to bacterial decomposition. Sanitary landfills are useful as the wastes are not attacked by rodents or insects. One precaution which needs to be taken is that landfills should not be located in areas that have high underground water levels as they may get polluted.
In the composting method, household and municipal wastes are decomposed by the aerobic method. The wastes are decomposed by microorganisms. This is a useful method of waste decomposition as wastes are decomposed by microorganisms into humus which adds to the fertility of the soil.
During incineration, municipal wastes are burned at a very high temperature. Many materials like metal do not get burnt. These are then recycled. This method however pollutes the air with fly ash and sulphur dioxide. It is also an expensive process as proper devices for controlling air pollution need to be installed.
This is a method in which wastes are segregated. Clothes, paper, glass, and metals are stored in different bins. Apart from these methods, effluents should be properly treated before they are discharged into the soil. Biofertilizers and manures should be used instead of chemical fertilizers.
Also, Read What is Water Pollution?