What on earth is not polluted? How far this is going to bother us and our coming generations? We need to be prepared when the coming generations point their fingers to us for contaminating the earth so badly. Even the soil, the richest form of earth is polluted, how? Let us look in to what is soil pollution, its causes, types, prevention and effects.
What is soil pollution?
Soil pollution is the addition of chemicals to the soil in quantities that are toxic to the environment and its residents. This addition is mostly by human activities such as mining, modern practices in agriculture, deforestation, indiscriminate dumping of human generated trash and unregulated disposal of untreated wastes of various industries
Pollution by agricultural practises has come up ever since the demand for food has increased, proportional to the increase in population. To increase the yield of farms and fields the farmers have had to resort to additional chemical fertilizers, pesticides, weedicides, hormonal treatments for the animals, nutrient laden feed and many such practices which changed the way farming was done traditionally.
Soil pollution does not stand alone. It mostly is accompanied by the water pollution and air pollution.
Causes of Soil Pollution
- Indiscriminate Use of Chemical fertilizers
These are mostly nitrogen and phosphorus based chemicals like ammonia and nitrates that are most often than not, used in larger than required quantities and tend to accumulate in the soil.
- Chemical pesticides
Controlling pests are a farmer’s need if a good crop is to be reaped. Pesticides and insecticides like organochlorines, organophosphates and carbonates are used regularly. These also contaminate the ground not only in the fields, but also in the places of manufacture, storage and disposal. They also tend to bio accumulate i.e. they collect in the body of the insects and then enter the food chain and lead to chronic poisoning of the higher level animals. Some pesticides also are absorbed naturally by the plants themselves and stored their different parts.
- Heavy metals
Cadmium, fluoride, radioactive elements like uranium are regularly found in the parent minerals from which the fertilisers are obtained. Dangerous metals such as Mercury, Lead, Arsenic, Chromium, and Nickel are seen in traces in Zinc rich wastes from the steel industries which are used as fertilizers. These are often not removed from the because of the high cost involved.
- Excessive tillage of the land
Overturning, digging or stirring leads to release of greenhouse gases produced in the ground such as nitrous oxide
- Soil erosion
Loss of soil material due to poor management causes soil to become infertile. Soil erosion is followed by deforestation, storm water runoff, overgrazing and excess of agriculture practices, constructions, mining. The soil sediments settling elsewhere on land or in water cause differences to occur in the environments there. In water it causes murkiness reducing visibility for fish and other animals sourcing their food. It leads to reduced penetration of sunlight and affects the process of photosynthesis causing reduction in oxygen levels of the water. Heavy pollutants and nutrients are bound to the sediment particles and carried into the water contaminating it. Faster rate of soil erosion changes the topography of a place.
- Animal management
The disposal of manure and other associated waste material from animal farms are also a reason for soil pollution. They cause pollution of the air as well as the water. 18 per cent of Greenhouse gases are said to be generated by farm animals. The large amounts of manure created, carry pathogens that are harmful for humans too.
- Landfills and other waste dumping issues.
Human generated sewage is a major cause for soil pollution. At the same time waste products such as plastics, glass, metals, Batteries, paper, fibres and rubber etc. add to the contamination as most of these are non-biodegradable. Much of the trash can be recycled such as paper, metal and glass, etc. Leaching of toxic materials occur at landfills. The more dangerous substances found in landfills are oils, battery metals, heavy metals from smelting industries and organic solvents.
- Acid rain
Air pollutants, sulphur dioxides, nitrous oxide and others combine with rain water, form acids and reach the soil. This is called acid rain. It reduces the pH of the soil ie it makes it acidic. It changes the nutrient content of the soil. These changes have adverse effects on the plants growing here, the insects and the other animal’s dependant on the land.
Mechanisms (Types of Soil pollution)
Leaching and Ground Water Poisoning
When chemicals accumulate in the soil, depending on its water solubility and soil structure it percolates through reaching the ground water, causing its contamination. This also depends on the rainfall. For example after applying pesticides on crops in sandy areas, if excessive irrigation is done , the pesticide chemicals leach into ground. Leaching occurs not only in the fields, but also at the manufacturing, mixing and disposal sites.
Only a fraction of fertilisers and other chemical additives are utilised on the fields. The major bulk mixes in the runoff water and flows into the nearby watercourses. This is mainly in the form of nitrates and phosphates.
Barrenness of the ground
Many times the ground becomes barren and cannot support any flora or fauna on it. Use of excessive fertilizer progressively reduces the nutrient content of the foods such as proteins and vitamins in grains and vegetables.
Prevention of soil pollution
- Managing and regulating the chemical waste disposal by industries is vital to soil health. Treatment of the wastes before disposal to remove chemicals and heavy metals at any cost must be done
- Prevention can never be a solo effort. The state governments, farmers’ organisations, collectives and cooperatives, educational institutions and conservation groups need to work together for regulating and reducing farming related soil pollution.
- Planning the application of fertilizer at the right time, in the right quantity with the correct methods can reduce the accumulation of chemicals.
- Planting certain grasses and clovers that can absorb and recycle the additional nutrients and prevent soil erosion. Planting rows of trees and shrubs around fields and along the borders of the stream or lake also help in the same way.
- Over tilling of the soil must be avoided to prevent soil erosion and soil compaction.
- Managing the correct disposal of human and animal wastes and treating the sewage before release makes a big difference in the magnitude of soil and water pollution
- Composting, solid liquid separation, anaerobic digestion and lagoons are different ways of managing animal manure. Of these anaerobic digestion is the most effective. It involves the use of anaerobic bacteria and heat. The products of this process are nutrient rich liquid used as fertiliser and methane gas that can be burned to produce electricity and heat. Anaerobic digestion is a best method for controlling odour associated with manure management.
- Afforestation or planting of more trees is always good for binding the soil.
Effects of soil pollution
Since soil pollution is not a lone standing entity, its effects are carried over as water pollution and air pollution. It affects every aspect of the environment and every organism from the earthworm to humans. Some of the adverse effects are as follows:
Since we are dependent on the land for our food, pollution from the soil is transferred to us in this manner. Bio accumulation of toxins occurs in our bodies, causing chronic poisoning, and leading to various diseases. Reproductive health, birth and developmental defects, neurologic effects, malnutrition, and mutations in the cells of the body leading to cancers; all these are on the increase today.
Growth of plants
Plants will not be able to adapt to sudden changes occurring in the soil. Fungi and bacteria found in the soils cannot bind the soil due to chemical changes and this causes soil erosion. Large tracts of land become barren; unable to support any life on it. Even the plants that do grow on these lands will absorb the toxins and transfer to the food chain.
Toxic dust rises from landfills along with foul odour, pollutes the air and causes adverse effects to the people who live near them.
Since every living being is dependent on the land for their nourishment, everyone is affected. As soil pollution continues unabated, malnourishment is a very real occurrence. The irony of high yield of crops versus decreased nutritional content in them is lost on many, who are in a position to bring about changes. Soil pollution also causes heavy economic losses. Medical expenses, rising costs of dwindling stocks of food, famines are all realities that have to be faced.
Much research and technological advances are helping to control soil pollution. Farmers are opting for more traditional organic methods of farming to reverse the damage caused to the lands. Hardier indigenous plants are now being grown again in the place of the hybrid ones. As awareness of one’s environment grows everyone must pitch in by following the motto of recycle, reduce and reuse. The consumerist in us must reduce and the conservationist must increase.