Soil pollution

Krishna Poudel

Senior Agriculture Instructor

Department of Plant Science

Shree Triveni Secondary School

Province 1, Nepal

Contact: +9779847016830

Krishna Poudel (researchgate.net)

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Concept and meaning:

Soil pollution is defined as the presence of toxic chemicals (pollutants or contaminants) in the soil, in very high concentrations to pose a risk to human health and the ecosystem.

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In simple words, alteration in the natural soil due to human activities is termed Soil Pollution

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Soil contamination can occur because of human activities or natural processes.

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It occurs due to many different activities such as overuse of pesticides where the soil will lose its fertility and the presence of excess chemicals that will increase the acidity or alkalinity of soil and hence degrading the quality of the soil.

Prevention and mitigation of soil pollution

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Organic farming for healthy soil

• Organic farming can be defined as an agricultural process that uses biological fertilizers and pest control acquired from animal or plant waste.
• Organic farming is a new system of farming or agriculture that repairs, maintains, and improves the ecological balance.
• There are various principles of organic farming. They are:
• Principle of health
• Principle of care
• Principle of fairness
• Principle of ecology

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Behavior of pesticides in soil

• Soil nutrients are important for plant growth and development. Plants obtain carbon, hydrogen and oxygen from air and water. But other necessary nutrients like nitrogen, phosphorus, potassium, calcium, magnesium, sulfur and more must be obtained from the soil.
• Farmers generally use fertilizers to correct soil deficiencies. Fertilizers contaminate the soil with impurities, which come from the raw materials used for their manufacture. Mixed fertilizers often contain ammonium nitrate (NH₄NO₃ ), phosphorus as P₂O₅ , and potassium as K₂O. For instance, As, Pb and Cd present in traces in rock phosphate mineral get transferred to super phosphate fertilizer.
• Since the metals are not degradable, their accumulation in the soil above their toxic levels due to excessive use of phosphate fertilizers, becomes an indestructible poison for crops. The over use of NPK fertilizers reduce quantity of vegetables and crops grown on soil over the years. It also reduces the protein content of wheat, maize, grams, etc., grown on that soil. The carbohydrate quality of such crops also gets degraded.
• Excess potassium content in soil decreases Vitamin C and carotene content in vegetables and fruits. The vegetables and fruits grown on over-fertilized soil are more prone to attacks by insects and diseaess

Behavior of inorganic contaminants in soil

• In general, solid waste includes garbage, domestic refuse and discarded solid materials such as those from commercial, industrial and agricultural operations. They contain increasing amounts of paper, cardboards, plastics, glass, old construction material, packaging material and toxic or otherwise hazardous substances. Since a significant amount of urban solid waste tends to be paper and food waste, the majority is recyclable or biodegradable in landfills.
• Similarly, most agricultural waste is recycled and mining waste is left on site. The portion of solid waste that is hazardous such as oils, battery metals, heavy metals from smelting industries and organic solvents are the ones we have to pay particular attention to. These can in the long run, get deposited to the soils of the surrounding area and pollute them by altering their chemical and biological properties. They also contaminate drinking water aquifer sources.
• More than 90% of hazardous waste is produced by chemical, petroleum and metal-related industries and small businesses such as dry cleaners and gas stations contribute as well.
• Toxic chemicals leached from oozing storage drums into the soil underneath homes, causing an unusually large number of birth defects, cancers and respiratory, nervous and kidney diseases.

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