Air & Water Pollution — Set 5

Correct Answer: C. Rapid cooling of the ground at night

During clear nights, the ground loses heat quickly, cooling the air immediately above it. If a warmer layer of air moves in above, it traps the cold, polluted air near the surface. This condition is responsible for persistent winter fog and high pollution levels in many cities.

Correct Answer: D. Fecal contamination

Coliform bacteria are found in the intestines of humans and warm-blooded animals. Their presence in water indicates potential contamination by sewage and the possible presence of other harmful pathogens. Testing for coliforms is a standard procedure for checking the safety of drinking water.

Correct Answer: A. Montreal Protocol

The Montreal Protocol was signed in 1987 and is considered one of the most successful environmental treaties. It has led to the near-total phase-out of substances that deplete the ozone layer. As a result, the ozone layer is showing signs of gradual recovery.

Correct Answer: C. Nitrogen oxides

Ground-level ozone is formed by the reaction of nitrogen oxides and volatile organic compounds in the presence of sunlight. Unlike the ozone in the stratosphere, this ozone is a harmful pollutant and a major component of smog. It can cause severe respiratory problems and damage crops.

Correct Answer: D. It can both cool and warm the atmosphere

Some particles reflect sunlight back into space, having a cooling effect, while dark particles like black carbon absorb heat. This dual role makes it complex to model their exact impact on global temperatures. Overall, they significantly influence the Earth's energy balance and cloud formation.

Correct Answer: A. Coal-fired power plants

Coal naturally contains sulfur, which is released into the air as sulfur dioxide when burned for electricity. India is one of the world's largest emitters of this gas due to its reliance on coal for energy. Installing 'flue-gas desulfurization' systems in plants can help reduce these emissions.

Correct Answer: C. Methane

Methane is produced by bacteria during the digestion process in cattle and the decomposition of waste in landfills. It is a powerful greenhouse gas with a high capacity to trap heat in the atmosphere. Capturing methane from landfills is a viable way to generate renewable energy.

Correct Answer: D. Eliminating Persistent Organic Pollutants (POPs)

POPs are toxic chemicals like DDT that remain in the environment for a long time and accumulate in the food chain. The Stockholm Convention is a global treaty to protect human health and the environment from these substances. It focuses on restricting and eventually eliminating their production and use.

Correct Answer: C. No gas used (It uses bacteria)

The Ames test is a biological assay to assess the ability of a chemical to cause mutations in the DNA of bacteria. Many chemical pollutants in water are tested this way to identify potential carcinogens. It is a standard preliminary screening tool used in toxicological research.

Correct Answer: D. Removing dissolved and suspended organic matter

Secondary treatment typically uses biological processes like activated sludge or trickling filters. Microorganisms consume the organic waste in the water, significantly reducing its BOD. The water is much cleaner after this stage but may still require further disinfection.