Soil Pollution

Sep 05, 2022, 16:45 IST

About one-fifth of the surface of the earth is exposed, solid and is called the land. The top surface layer of this land, capable of supporting plant growth is called soil. Over million years of time, the rocks at or near the surface of the earth are broken down by various physical, chemical and some biological processes to form fine soil particles.

Soil is a complex mixture, having five components: mineral matter – 45%, organic matter – 5%, water – 25%, air – 25% and living organisms. All these components are essential for plant growth. Temperature variations due to radiations of the sun, rainwater, winds and living organisms influence the formation of soil from the rocks.

Soil formation involves two processes: (i) weathering, and (ii) paedogenesis. Breakdown of bigger rocks into small, fine mineral particles is called weathering. It may occur due to physical, chemical or biological means. Paedogenesis involves the decomposition of organic materials by bacteria and fungi of decay and leads to humification and mineralization.

Soil profile shows four distinct layers, called horizons. Top soil forms horizon A. The horizon B has soil particles smaller and usually more compact than in the horizon C which consists of the weathered material. The latter is derived from the intact parent rock. The parent rock forms the horizon .

Soil Pollution Definition

Soil pollution refers to soil contamination with anomalous concentrations of toxic substances.

It is a serious environmental problem because it harbors many health risks. E.g., exposure to soil containing high benzene concentrations increases the risk of leukemia. It is important to note that all soils contain compounds that are harmful/toxic to humans and all other living organisms. Since the concentration of such substances in unpolluted soil is low enough to pose no threat to the surrounding ecosystem. Thus, when the concentration of one or more such toxic substances is high sufficient to cause harm to living organisms, the soil is considered contaminated.

Types of Soil

• Agricultural soil pollution is caused by excessive use of insecticides and pesticides.
• Soil pollution by industrial discharge of chemicals from production and extraction of goods.
• Poor management/Solid waste soil pollution or inefficient disposal of waste.
• Soil Pollution due to urban activities. etc

Soil Contamination

All soils consist of compounds that are harmful to humans and other living organisms. However, the concentration of these substances in unpolluted soil is so low that they do not threaten the environment. Still, when the concentration of such toxic substances increases to the extent that they cause harm to living organisms, the soil is considered contaminated.

soil contamination can occur as a result of human activity or as a result of natural processes. However, it is mainly caused by human activity. This happens as a result of many different activities, such as excessive use of pesticides, the soil will also lose its fertility, and the presence of excess chemicals will increase the alkalinity or acidity of the soil and thereby degrade the quality of the soil.

Causes of Soil Pollution

Soil pollution can be classified into two types:

1. Naturally caused soil pollution
2. Anthropogenic soil pollution (caused by a human)

Natural Pollution of Soil

In some extremely rare processes, some pollutants naturally accumulate in the soil. This can occur due to differential deposition of soil by the atmosphere. Another way this type of soil pollution can happen is by transporting soil pollutants with rainwater. Let's take an example of natural soil pollution as the accumulation of compounds containing perchlorate anion (ClO₄^–) in some dry arid ecosystems. It is also important that some contaminants may be naturally produced in soil under certain environmental conditions. For example, perchlorates can form in soils containing chlorine and certain metals during a thunderstorm.

Anthropogenic Soil Pollution

Almost all the cases of soil pollution are anthropogenic. Various human activities can lead to soil contamination. Some processes are listed below.

• Demolition of old buildings may involve asbestos contamination of the surrounding soil.
• Using lead-based paints in construction activities can also contaminate the soil with dangerous lead concentrations.
• Gasoline and diesel spills during transport can contaminate the soil with hydrocarbons contained in the oil.
• Activities associated with metal casting factories (foundries) often result in the dispersion of metal contaminants into surrounding soils.
• Underground mining can cause soil contamination with heavy metals.
• Improper disposal of highly toxic industrial/chemical waste can pollute the soil. E.g., the storage of toxic wastes in landfills can result in waste seeping into the soil. This waste can further pollute groundwater.
• Chemical pesticides contain several dangerous substances. Excessive and ineffective use of chemical pesticides can result in serious soil pollution.
• Wastewater produced in urbanized areas can also contaminate soil (if not properly disposed of). These wastes may also consist of several carcinogenic substances.

Negative Consequences of Soil Pollution

Soil pollution hides a wide range of negative consequences that affect plants, animals, people and the ecosystem as a whole. Since children are more susceptible to disease, polluted soil poses a greater threat to them. Some important effects of soil pollution are detailed in this subsection.

Effects on Human Beings

Soil contaminants can exist in all three stages (solid, liquid, and gas). Therefore, these contaminants can enter the human body through several channels, such as direct skin contact or inhalation of contaminated soil dust.

The short-term effects of human exposure to pollutes soil include

• Headache, nausea, and vomiting.
• Cough, chest pain, and wheezing.
• Skin and eye irritation.
• Fatigue and weakness.

Several long-term illnesses have been linked to soil pollution. Some such diseases are listed below.

• Exposure to high levels of lead can permanently damage the nervous system. Children are especially sensitive to leadership.
• CNS (central nervous system) depression.
• It damage to organs such as the liver and kidney.
• Higher risk of cancer.
• It may be noted that many soil pollutants, such as petroleum hydrocarbons and industrial solvents, have been linked to birth defects in humans. Soil pollution can thus have several negative effects on human health.

Effects on Plants and Animals

Since a reduction in nutrient availability often accompanies soil pollution, plant life ceases to thrive in such soils. Soils contaminated with inorganic aluminum can be toxic to plants. This type of pollution also often increases the salinity of the soil, making it inhospitable for plant growth.

Plants grown in contaminated soil can accumulate high concentrations of soil pollutants through a process known as bioaccumulation. When herbivores consume these plants, any accumulated pollutants pass through the food chain. This can lead to the loss/extinction of many desirable animal species. These pollutants can also eventually reach the top of the food chain and manifest as diseases in humans.

Effects on the Ecosystem

• Since volatile contaminants in soil can be carried into the atmosphere by winds or seep into underground water supplies, soil pollution can directly contribute to air and water pollution.
• It also contributes to acid rain (by releasing huge amounts of ammonia into the atmosphere).
• Acidic soils are also inhospitable to several microorganisms that improve soil texture and aid in decomposing organic matter. The negative effects of soil pollution affect the soil quality and texture.
• Crop yields are greatly affected by this form of pollution. In China, more than 12 million tonnes of grain (worth approximately US$2.6 billion) was found unfit for human consumption due to heavy metal contamination (according to studies conducted by China Dialogue).

Prevention of Soil erosion

• Intensive cropping
• Sowing grasses and planting of xerophytes in dry soils.
• Terrace farming in hilly regions.
• Proper drainage canals around the fields.
• Making strong embankments along the river beds.

Frequently Asked Question (FAQs)

Q1. What is Soil Pollution?

Ans. The presence of toxic chemicals (contaminants or pollutants) in the soil in high enough concentrations to pose a risk to humans is known as Soil Pollution.

Q2. How can soil pollution be controlled?

Ans. Properly recycle batteries, eat sustainable foodstuffs, produce homemade compost and dispose of drugs in the places authorized for this purpose. Encourage a more eco-friendly model for the industry, farming, and stock breeding, among other economic activities.

Q3. How does soil pollution affect human life?

Ans. Pollutants in soil, groundwater, and the food chain can cause various diseases and excess mortality in humans, from short-term acute effects, such as intoxications or diarrhea, to long-term chronic effects, like cancer.

Q4. How does soil pollution affect the economy?

Ans. Quantifiable economic losses due to soil pollution are contamination of food products and loss of marketability, biodiversity reduction of water quality, loss of soil productivity, and decreased crop yields.

Q5. Which country has the most soil pollution?

Ans. The most polluted country in the earth is Bangladesh, with an average PM2.5 concentration of 77.10, a decrease from 97.10 in 2018 and 83.30 in 2019.

Q6. Where does soil pollution occur?

Ans. Junkyards, Landfills and waste disposal sites pose high risk of soil contamination, like industrial sites. These areas often contain a large mix of contaminant types like lead, arsenic, and petroleum products.