Pollution & waste

Answer: (d) 1, 2 and 3

All three statements are correct, because farming is a major source of reactive nitrogen. Fertilised soils release nitrous oxide, and manure and urine from cattle and poultry give off ammonia.

• ✓ 1. When reactive nitrogen such as fertiliser reaches the soil, microbes convert part of it into nitrous oxide, an oxide of nitrogen and a greenhouse gas.
• ✓ 2. Much of the protein that cattle eat is lost in manure and urine, and this nitrogen escapes as ammonia and other nitrogenous gases.
• ✓ 3. Poultry waste is rich in nitrogen, and under aerobic conditions it can evaporate as ammonia, which is a reactive nitrogen compound.

Remember · Agriculture is a big source of reactive nitrogen: soils give nitrous oxide, while cattle and poultry manure gives ammonia.

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Answer: (b) 2 and 3 only

Statements 2 and 3 are correct. Blending hydrogen, which has no carbon, into CNG lowers carbon dioxide and hydrocarbon emissions, and India's trials and rules use a blend of about 18% hydrogen by volume, which is within one-fifth. H-CNG does not eliminate carbon monoxide and is not cheaper than plain CNG.

• ✗ 1. H-CNG is still mostly natural gas, a carbon fuel, so it can lower carbon monoxide but cannot eliminate it. Official pages describe the benefit as emissions reduction, not elimination.
• ✓ 2. Part of the fuel is carbon-free hydrogen, so less carbon is burnt per unit of energy and the blend gives lower carbon dioxide and hydrocarbon emissions; the Petroleum Ministry calls H-CNG an interim technology for emissions reduction.
• ✓ 3. The Road Transport Ministry allowed H-CNG with an 18% hydrogen mix in CNG engines, which is under one-fifth (20%) by volume; the Delhi bus trials also used 18%.
• ✗ 4. Making the blend is costly: the Petroleum Ministry notes that the high cost of producing and blending hydrogen offsets the fuel-economy savings over plain CNG, and its Secretary called commercial viability the main challenge.
• • Since then After the exam year, the Road Transport Ministry notified (GSR 585(E), 25 September 2020) H-CNG with an 18% hydrogen mix as an automotive fuel.

Remember · H-CNG is CNG blended with up to about 18% hydrogen by volume: it lowers emissions but does not remove them, and it is costlier than plain CNG.

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Answer: (c) The Rules provide for exact and elaborate criteria for the identification of sites for landfills and waste processing facilities.

Option (c) is correct because Schedule I of the Solid Waste Management Rules, 2016 gives detailed site-selection criteria for sanitary landfills, such as minimum distances from rivers, ponds, highways, habitations and airports. The other three options misstate the rules.

• ✗ (a) Rule 4 asks every waste generator to segregate waste into three streams: bio-degradable, non bio-degradable and domestic hazardous waste. There is no five-way split.
• ✗ (b) Rule 2 applies the Rules far more widely than 'only' urban local bodies, notified towns and industrial townships. It also covers census towns, outgrowths of urban agglomerations, railways, airports, ports, defence establishments, SEZs and more.
• ✓ (c) Schedule I lays down criteria such as a landfill 100 metres from a river, 200 metres from a pond, highways, habitations, public parks and water supply wells, and 20 km from airports.
• ✗ (d) The Rules contain no ban on moving waste between districts. They say the State Pollution Control Board regulates inter-State movement of waste.
• • Since then The Solid Waste Management Rules, 2016 have since been superseded by the Solid Waste Management Rules, 2026, notified in January 2026 and in force from 1 April 2026. The new Rules make four-stream segregation (wet, dry, sanitary and special care waste) mandatory (PIB).

Remember · Under the 2016 Rules, waste is segregated into three streams and Schedule I fixes landfill siting distances; the 2026 Rules replaced these with four-stream segregation.

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Answer: (c) The e-Waste (Management and Handling) Rules, 2011

India's e-Waste (Management and Handling) Rules, 2011 introduced extended producer responsibility (EPR), which makes the producer of electrical and electronic equipment answerable for the product until its safe disposal after use. The rules were notified in May 2011 and came into force on 1 May 2012.

• ✓ (c) The official guidelines on these rules say they place the main responsibility for e-waste on producers of electrical and electronic equipment by introducing the concept of extended producer responsibility.
• ✗ (a) The 1998 bio-medical waste rules pre-date the e-waste rules and are not the ones credited with bringing in EPR.
• ✗ (b) The 1999 recycled plastics rules likewise pre-date the 2011 e-waste rules, which are the ones that introduced EPR in India.
• ✗ (d) The Food Safety and Standards Regulations, 2011 deal with food safety, not with waste, so producer responsibility for end-of-life products is not their feature.

Remember · EPR = the producer stays responsible for a product until its safe disposal. In India it came with the e-Waste Rules, 2011 (in force 1 May 2012).

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Answer: (a) 1 only

Only the Aral Sea fits. From the 1960s the Soviet Union diverted its feeder rivers, the Amu Darya and Syr Darya, to irrigate cotton, and the lake that was once the world's fourth largest broke into small remnants. The Black Sea and Lake Baikal have not shrunk in this way.

• ✓ 1. Irrigation diversions starved the Aral Sea (on the Kazakhstan–Uzbekistan border) of inflow; satellite images show it was already a fraction of its 1960 extent by 2000.
• ✗ 2. The Black Sea, a large inland sea linked to the Mediterranean through the Bosporus, faces pollution problems but has not dried up.
• ✗ 3. Lake Baikal in Siberia, the world's deepest lake, still holds its vast volume of fresh water; it has not shrunk immensely.

Remember · Aral Sea: once the world's fourth-largest lake, fed by the Amu Darya and Syr Darya; shrank drastically after Soviet-era irrigation diversions from the 1960s.

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Answer: (b) 2 and 3 only

Heavy sand mining harms groundwater in two ways: it can pollute it and it can pull the water-table down. It does not lower river salinity; near the coast it makes salt-water intrusion more likely.

• ✗ 1. Removing sand deepens the channel and weakens natural barriers, so salt water can enter aquifers; UNEP lists 'salination of aquifers' as a result of sand extraction. Salinity goes up, not down.
• ✓ 2. The sand layer filters water that seeps into the ground. The MoEFCC guidelines say mining can pollute groundwater by thinning this filter material, especially over recharge fissures.
• ✓ 3. Mining lowers the riverbed and river level, and groundwater in the adjoining flood plain drains towards it, so the water-table falls. The guidelines record this as a listed effect.

Remember · Heavy riverbed sand mining lowers the water-table, weakens the sand filter that protects groundwater, and raises salt intrusion risk near the coast.

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Answer: (c) 1 and 3 only

Bioremediation speeds up the natural breakdown of pollutants by microbes, and microbes can be genetically engineered for the job. But microbes break down organic compounds; metals such as cadmium and lead are elements that cannot be degraded, only changed in form or immobilised, so statement 2 overclaims.

• ✓ 1. It uses microorganisms that feed on or co-metabolise contaminants, boosting the same biodegradation that happens in nature by supplying nutrients, oxygen or other electron acceptors.
• ✗ 2. Bioremediation is described as degrading organic contaminants. Heavy metals cannot be broken down by microbes, so 'readily and completely treated' is wrong; at best microbes change their chemical form.
• ✓ 3. Biotechnology uses genetically modified microbes for bioremediation; in 1971 Ananda Mohan Chakrabarty developed a bacterium that could break down oil spills.

Remember · Bioremediation = microbes degrading organic pollutants (oil, solvents, pesticides); engineered microbes help. Heavy metals cannot be degraded, only transformed or immobilised.

📘 Read it in NCERT: Class 12 Biology, Ch 10 (practise this chapter) · Class 8 Curiosity, Ch 2 (practise this chapter)

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Answer: (c) Pollution assay in aquatic ecosystems

BOD is the amount of oxygen that bacteria would use up to break down the organic matter in a sample of water, so it is a standard test of how polluted water is. A higher BOD means more organic pollution.

• ✓ (c) BOD measures the oxygen consumed by microbes in decomposing the organic matter in water, so it works as an indirect measure of that matter. The greater the BOD of waste water, the greater its polluting potential.
• ✗ (a) BOD is a test on water samples. It has nothing to do with the oxygen carried in blood.
• ✗ (b) BOD says nothing about oxygen in forests. It tells us how much oxygen microbes need in water that carries organic waste.

Remember · BOD is oxygen bacteria need to decompose the organic matter in water. Higher BOD means more pollution; sewage treatment aims to bring it down.

📘 Read it in NCERT: Class 12 Biology, Ch 8 (practise this chapter) · Class 12 Biology, Ch 8 (practise this chapter)

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Answer: (b) 2 only

The Climate and Clean Air Coalition (CCAC) is a voluntary partnership convened within the UN Environment Programme (UNEP), not an initiative of the G20, so statement 1 is wrong. It targets methane, black carbon and hydrofluorocarbons, so statement 2 is correct.

• ✗ 1. The CCAC was founded in 2012 and is convened within UNEP. It is a voluntary partnership of governments, intergovernmental organisations and non-governmental organisations, not a project of the G20 group.
• ✓ 2. The CCAC works to cut short-lived climate pollutants: methane, black carbon, hydrofluorocarbons and tropospheric ozone. These stay in the air only briefly but heat the planet strongly and harm air quality.

Remember · CCAC (2012) is a UNEP-convened voluntary coalition on short-lived climate pollutants: methane, black carbon, HFCs and tropospheric ozone. It is not a G20 body.

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Answer: (b) 2, 3 and 4 only

Carbon monoxide, nitrogen dioxide and sulfur dioxide are used in India's National Air Quality Index; carbon dioxide and methane are not. The index is built from eight pollutants for which short-term air quality standards exist: PM10, PM2.5, NO2, SO2, CO, ozone, ammonia and lead.

• ✗ 1. Carbon dioxide is a greenhouse gas, not one of the eight pollutants in the National AQI.
• ✓ 2. Carbon monoxide (CO) is one of the eight AQI pollutants.
• ✓ 3. Nitrogen dioxide (NO2) is one of the eight AQI pollutants.
• ✓ 4. Sulfur dioxide (SO2) is one of the eight AQI pollutants.
• ✗ 5. Methane is a greenhouse gas and is not among the eight pollutants used for the AQI.

Remember · National AQI pollutants: PM10, PM2.5, NO2, SO2, CO, O3, NH3, Pb. No CO2 and no methane.

📘 Read it in NCERT: Class 8 Curiosity, Ch 8 (practise this chapter)

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