What is soil pollution?
Soil pollution or soil contamination is a part of land degradation caused by acid rain, excess and wrong use of agricultural fertilizer, insecticides ( the chemical compounds that kill insects), and herbicides (chemical substances that kill plants) to affect the natural soil environment. Petroleum, polynuclear hydrocarbon, and heavy metals are the most common substances which cause soil or water pollution.
All the soil contains different types of harmful or toxic polluted substances for human beings and other living organisms. However, the natural concentration of such substances does not threaten the surroundings of our ecosystem. Soil pollution effect or damage a living organism, when the concentration of one or more of such toxic molecule is large enough.
Sources of soil pollution
Different types of polluting substances or sources are responsible for soil pollution in our environment or ecosystem. Acidic or alkaline water molecules, repeated or excessive use of fertilizer, inadequate drainage systems in agricultural fields, spraying of insecticides, and herbicides are the main factors responsible for soil pollution. The different types of sources and their effect are discussed below in this learning chemistry topic.
Effects of acid rain on soil
We know that the air of our environment contains gaseous sulfur dioxide (SO2) and nitrogen dioxide (NO2). Sulfur dioxide present in the air undergoes photolytic or catalytic oxidation to form sulfur trioxide (SO3). It reacts with rainy water or moisture to form sulfuric acid rain ( SO3 + H2O → H2SO4) is responsible for soil and water pollution.
NO2 also reacts with rainy water or moisture in presence of oxygen or ozone produces nitric acid (HNO3) rain. The sulfuric acid and nitric acid formed by the above formula come down to the atmosphere to damages standing crops or changes the pH scale of soil.
Effect of fertilizer on soil
Repeated and excess use of the same fertilizer pollutes the soil of our environment. Some of the fertilizer increases the acidity of soil and some made the soil alkaline.
Which fertilizer increases the acidity of soil?
When we used ammonium sulfate [NH4(SO4)] fertilizer for the production of crops into the soil, again and again. The ammonium ion (NH4+) is used up by crops but sulfate ion (SO4-2) gets accumulated into the soil responsible for increases the acidity of the soil. The sulfate ion makes the soil highly acidic, hence the soil unfit for plant growth.
How to reduce soil acidity?
Soil acidity can be easily removed by adding basic material like limestone to neutralize the soil. Calcium carbonate or limestone is widely used because it is easy to handle and economically lower than other basic substances.
Fertilizer for alkaline soil
If we use sodium nitrate (NaNO3) or potassium nitrate (KNO3) again and again, the nitrate ion (NO3–) is used up by successive crops but sodium and potassium ions get accommodated into the soil. These fertilizers make the soil alkaline and hence the soil cannot be used for the high production of food.
Drainage system in agriculture
We use a lot of water for irrigation along with fertilizer, but there should be a good drainage system for the outlet of unused water. Otherwise, the soil becomes highly saline (salt-containing) which affects the growth of plants and is responsible for soil pollution. Therefore, the inadequate drainage system in the agricultural field is another source of soil pollution.
Pesticides and herbicides
When we speared different types of pesticides and herbicides to save the fruits and vegetable plants from harmful insects and herbs. Pesticides and herbicides enter into the living tissue of the growing plants in our environment. The pesticides and herbicides cause soil pollution and toxic effects on our health, when we eat these grains, fruits, or vegetables, it may damage our heart, kidney, etc. Therefore, we advised that before eating these types of polluted foods growing from soil pollution, they should be washed with a sufficient quantity of water.
Prevention of soil pollution
Soil pollution can be prevented or minimized by the following methods,
- Reducing the emission of sulfur dioxide and nitrogen dioxide causes acid rain to increase soil acidity.
- The use of excess nitrate, sulfate, and phosphate fertilizer should be avoided because it increases or decreases the acidity of the soil.
- To minimize the use of synthetic detergents, properly recycle batteries and other harmful chemicals which cause soil pollution.
- Before throwing industrial wastes into the soil, they should be treated chemically to neutralize harmful substances present on them. These should be throwing the places which are authorized for them.
- Encourage for the eco-friendly model for the industry, farming.
- Using proper drainage system for agriculture.
- Improving urban planning and waste water treatment.
- Decreasing the use of harmful pesticides and herbicides that cause soil pollution.