What is water pollution?

Water pollution occurs when water bodies are contaminated with dangerous elements such as sewage, silt and chemicals. These contaminants are a result of human activity.

Case study - The Ganga

The Ganges is one of India's longest perennial rivers, flowing through 11 States in India. It is vital to several people’s survival and daily requirements. However, according to the World Wildlife Fund, Ganga is one of the world's 10 most threatened rivers. 

The Ganga Action Plan

In 1985, the government adopted the Ganga Action Plan to lower river pollution. However, population growth and industrialisation have already irreversibly ruined this majestic river. In 2016, the Indian government announced the National Mission for Clean Ganga (NMCG).

How does water get polluted?

1. Industries

Many businesses pollute rivers and streams by dumping hazardous chemicals into them. Oil refineries, paper mills, textile and sugar mills, and chemical plants are a few examples. To prevent this, there are laws in place. 

2. Pesticides and chemicals

Crops necessitate the use of pesticides and herbicides. These chemicals dissolve in water and are washed into water bodies passing through the farms. They also pollute the groundwater when they leak into the soil.

3. Untreated Sewage

Untreated sewage is sometimes dumped into rivers. This may include food trash, detergents, and microbes. Sewage-contaminated water may contain bacteria, viruses, fungus, and parasites that cause diseases such as cholera, typhoid, and jaundice.

Answer 1:

Soil erosion is induced by water and wind as a result of three basic factors:

• Deforestation as a result of increased population and industrialisation
• Overgrazing by enormous animal populations has degraded flora and resulted in barren ground
• Ploughing for agriculture loosens the soil and destroys its natural riches

Answer 2:

Pollutants such as sulphur dioxide and nitrogen dioxide are emitted by factories. Sulphuric acid and nitric acid are formed when these gases react with water vapour in the environment. These are washed down with the rain, making it acidic. Acid rain is hazardous to our health because it destroys buildings and harms crops and vegetation.

Examples:

• It impacts monuments such as the Taj Mahal
• Plant growth is hampered.
• Humans' eyes are irritated as a result of pollutants in the rain

Answer 3:

The greenhouse effect is so named because the Earth's atmosphere works like a glass greenhouse, allowing sunlight to enter but trapping heat emitted by plants in the form of infrared radiations. Carbon dioxide prevents heat from escaping, which leads to global warming. 

Answer 4:

The Sun’s infrared heat rays can travel through the carbon dioxide in the atmosphere. They are not permitted to exit the atmosphere after being reflected by the Earth. The absorbed heat rays from a thick blanket over the planet. This is called the greenhouse effect.

Answer 5:

Fertilisers contain nitrates and phosphates, which are washed into the ponds. They are eaten by algae and bacteria, which disintegrate after they die. This process consumes a lot of oxygen, making it harder for other aquatic species to live. 

Answer 6:

The Supreme Court has directed industries to utilise greener fuels such as compressed natural gas (CNG) and liquefied petroleum gas (LPG). In addition, autos in the Taj zone are required to use unleaded gasoline. 

Answer 7:

The marble of the Taj Mahal has turned yellow and is deteriorating as a result of acid rain. This is described as "Marble Cancer." 

Answer 8:

The Ganga Action Plan was established in 1985 to safeguard the Ganga River. Its goal is to lower pollution levels by processing home sewage, constructing electric crematoria, and eliminating industrial waste. 

Answer 9:

Many enterprises dump hazardous chemicals into rivers and streams, contaminating the water. Chemicals such as arsenic, lead, and fluorides are emitted into rivers by oil refineries, textile mills, paper mills, and sugar mills. 

Answer 10:

Fertilisers increase agricultural productivity. However, these chemicals dissolve in water and are washed into bodies of water from the fields. These leach into the ground and harm groundwater. 

Answer 11:

Sewage that has not been treated leaks into groundwater. It can cause diseases including typhoid, cholera, and jaundice because it contains bacteria, viruses, fungus, and parasites.

Answer 12:

Yes, hot water can pollute the environment. It boosts the temperature of the water, which harms the creatures and plants that live in it. 

Answer 13:

Suspended particles are introduced into the atmosphere by:

• Automobiles that run on gasoline and diesel
• Several factories
• Nuclear power plants
• Ore extraction

Answer 14:

Water harvesting is the practice of collecting and storing rainwater. It is accomplished by directing rainwater from buildings’ roofs into a deep trench in the ground. Groundwater levels are raised in this manner. Rainwater is not permitted to enter the rivers.

Answer 15:

Catalytic converters installed in automobiles reduce air pollution. It converts toxic exhaust gases such as carbon monoxide and nitrogen dioxide into harmful nitrogen, carbon dioxide, and water.

Answer 1:

The progressive rise in the average temperature of the Earth's atmosphere is known as global warming. The enhanced greenhouse effect is to blame for this.

The following variables contribute to an increase in the amount of carbon dioxide in the atmosphere:

• Deforestation
• Increased human activity
• Industrialisation

Climate change is occurring. If current trends continue, glaciers are predicted to melt and ocean levels to rise.

Answer 2:

The following steps can be taken to mitigate air pollution:

• Vehicles should run on CNG or unleaded fuel
• Say no to fireworks during Diwali
• Using alternate energy sources instead of fossil fuels
• Growing more trees
• Not burning dried leaves and composting them instead

Answer 3:

The following factors contribute to air pollution:

• Forest fire smoke and dust
• Eruptions of volcanoes
• Emissions from automobiles
• Factories and power plants
• The combustion of firewood and dung cakes

Answer 4:

• Gaseous pollutants such as sulphur dioxide and nitrogen dioxide are emitted by petroleum refineries
• Because coal is burned in power plants, sulphur dioxide is released
• Power plants emit microscopic gas particles 
• Particles are also released into the atmosphere as a result of industrial processes.

Answer 5:

Water can be made safe to drink by following these steps:

• At home, it is filtered using, for example, a candle type filter
• To kill bacteria, boil the water
• By using chlorine pills or bleaching powder
• Ozone gas or iodine can be utilised
• Some water treatment systems employ ultraviolet light

Answer 6:

On a personal level,

• We save water by not wasting it
• Water can be reused
• Water must be recycled
• When the water is heated, close the faucets
• To avoid leaks, repair the faucets

Answer 7:

Van Mahotsav is an annual tree-planting initiative that takes place in July.

More trees are planted during this time. Planting trees has the following benefits:

• The greenhouse effect is lessened.
• The number of dust particles in the air is lowered.

NCERT Solutions for Class 8 Science Chapter 18 MCQs 

Students can use the NCERT Solutions for Class 8 Science Chapter 18 to get straightforward and step-by-step answers to the questions in the textbook. The answers are useful in understanding how to answer questions in the CBSE board exams.