STD 8 SCIENCE LESSON
TOPIC : ENVIRONMENT
SUBTOPIC: SOIL POLLUTION
What is Soil Pollution?
Soil pollution refers to the contamination of soil with toxic substances. It is a serious environmental concern since it harbours many health hazards. For example, exposure to soil containing high concentrations of benzene increases the risk of contracting leukaemia. An image detailing the discolouration of soil due to soil pollution is provided below.
It is important to understand that all soils contain compounds that are harmful/toxic to human beings and other living organisms. However, the concentration of such substances in unpolluted soil is low enough that they do not pose any threat to the surrounding ecosystem. When the concentration of one or more such toxic substances is high enough to cause damage to living organisms, the soil is said to be contaminated.
The root cause of soil pollution is often one of the following:
- Agriculture (excessive/improper use of pesticides)
- Excessive industrial activity
- Poor management or inefficient disposal of waste
The challenges faced in soil remediation (decontamination of soil) are closely related to the extent of soil pollution. The greater the contamination, the greater the requirement of resources for remediation.
What are the Pollutants that Contaminate Soil?
The different types of pollutants that are found in contaminated soil are listed in this subsection.
Heavy Metals
The presence of heavy metals (such as lead and mercury, in abnormally high concentrations) in soils can cause it to become highly toxic to human beings. Some metals that can be classified as soil pollutants are tabulated below.
| Toxic Metals that Cause Soil Pollution |
| Arsenic | Mercury | Lead |
| Antimony | Zinc | Nickel |
| Cadmium | Selenium | Beryllium |
| Thallium | Chromium | Copper |
These metals can originate from several sources such as mining activities, agricultural activities, electronic waste (e-waste), and medical waste.
Industrial Waste
The discharge of industrial waste into soils can result in soil pollution. Some common soil pollutants that can be sourced to industrial waste are listed below.
- Chlorinated industrial solvents
- Dioxins produced from the manufacture of pesticides and the incineration of waste.
- Plasticizers/dispersants
- Polychlorinated biphenyls (PCBs)
The petroleum industry creates many petroleum hydrocarbon waste products. Some of these wastes, such as benzene and methylbenzene, are known to be carcinogenic in nature.
Pesticides
Pesticides are substances (or mixtures of substances) that are used to kill or inhibit the growth of pests. Common types of pesticides used in agriculture include:
- Herbicides – used to kill/control weeds and other unwanted plants.
- Insecticides – used to kill insects.
- Fungicides – used to kill parasitic fungi or inhibit their growth.
These chemicals pose several health risks to humans. Examples of health hazards related to pesticides include diseases of the central nervous system, immune system diseases, cancer, and birth defects.
ANSWER THESE QUESTIONS
1. What is soil pollution?
