Environment and Ecology Mixed Practice — MCQs with Answers (Set 20)

The best answer here is 0.5 percent. The idea is small area, big job. A conference abstract at the European Geosciences Union gives about 0.2% of the ocean surface for coastal vegetated habitats. That is closest to the 0.5 percent option. The same abstract says they contribute 50% of carbon burial in marine sediments. The 75, 40 and 15 percent options are wrong because they are far too large for such thin coastal strips. Memory hook: tiny strip, half the burial.

The correct answer is mangroves, salt marshes and seagrass meadows. NOAA names sea grasses, mangroves and salt marshes as the coastal systems that capture and hold carbon. IUCN names the same three. The rainforest option is wrong because those are land forests and grasslands. The coral, desert and tundra option is wrong because none of those is a blue carbon habitat. The glacier option is wrong because ice does not store carbon the way rooted plants do. Memory hook: tidal forest, tidal grass, underwater grass.

The correct answer is carbon captured by oceans and coastal ecosystems. NOAA defines blue carbon as the carbon captured by the world’s ocean and coastal ecosystems. The forest and farm soil option is wrong because that is land carbon. The petroleum and gas option is wrong because that is fossil carbon. The atmosphere option is wrong because air carbon is the gas that these habitats take out. Memory hook: blue means sea and coast.

Steel slag genuinely works for road base construction, agricultural soil improvement, and cement production. All three are correct.

Furnace oil’s high sulphur content genuinely produces sulphur dioxide on combustion. The other three pairs are the documented exam-trap fakes for their respective topics.

Magnetite from brake pads forms through friction between the pad and rotor, unlike the other four sources, which all trace back to combustion.

Maher and colleagues found magnetite nanoparticles in human brain tissue. They said such exposure might need examining as a hazard. The concern is neurodegenerative disease, such as Alzheimer’s disease. The link is not proven. A 2021 study of Manchester brains found no significant difference in magnetite levels between Alzheimer’s and non-Alzheimer’s cases.

Maher and colleagues say magnetite particles smaller than about 200 nanometres can enter the brain directly through the olfactory bulb. A 2025 review says nanoparticles inhaled through the nose may travel along the olfactory nerves and bypass the blood-brain barrier entirely. Skin absorption and the digestive system are not the route the 2016 paper describes.

Microwave ovens are not a magnetite source in UPSC’s key for the 2021 question, which also leaves out telephone lines. The studies link pollution magnetite to combustion and friction heating. That covers vehicle brakes and engines, and coal-burning power plants.

Magnetite is a strongly magnetic iron oxide with iron in two forms, Fe2+ and Fe3+. Its formula is Fe3O4. Maher and colleagues describe brain magnetite as a mixed Fe2+/Fe3+ iron oxide. A study of coal fly ash also identified magnetite as Fe3O4. The other options are not iron oxides.

UPSC’s official key for CSP 2021, General Studies Paper I, Series A, gives option (b), 1, 2 and 4 only. Brakes, engines and power plants are the sources. Maher and colleagues tie pollution magnetite to combustion and friction heating, such as brake pad friction. Ripley and colleagues name vehicle tailpipe emissions and brake wear. Hammond and colleagues name coal-burning power plants. Microwave stoves and telephone lines are not in the key.

EPCA says the key substitutes for furnace oil and pet coke are natural gas and electricity. It adds that natural gas has no emission standards, because it is accepted as cleaner, with no PM or SO2 emissions. In 2017, gas companies said pipelines were laid but demand was low because furnace oil and pet coke were cheaper.

IS 1593:2018 allows furnace oil up to 3.5 to 4.5 per cent sulphur by mass, depending on grade. EPCA’s 72nd report gives 15,000 to 23,000 ppm for furnace oil. EPCA called 10 ppm low-sulphur in 2017. Burning a sulphur-rich fuel releases sulphur dioxide.

Bharat Petroleum lists these uses: firing boilers, thermic fluid heaters, industrial furnaces, foundry and glass furnaces, and slow-speed engines for captive power generation. Hindustan Petroleum says its LSHS is used mainly in heavy industry, steel plants and power plants. A 3 March 2017 Environment Ministry affidavit said cement and other industries with SO2 and NOx controls may use furnace oil and pet coke. EPCA disagreed and recommended a strict ban in the NCR. The other options name farms and IT firms, or say there is no industrial use, and the Bharat Petroleum list contradicts them.

Furnace oil is a residual fuel. Bharat Petroleum says it is made mainly from the heavier components from the crude distillation unit. The US EIA says the heaviest fractions settle at the bottom of the refinery tower.

Statement 1 is true: Bharat Petroleum says furnace oil is made by blending mainly the heavier components from crude distillation. Statement 2 is true: Bharat Petroleum lists boilers, furnaces and captive power engines among its uses. Statement 3 is true: EPCA’s 72nd report gives 15,000 to 23,000 ppm of sulphur for furnace oil. UPSC’s key for CSP 2021 Q18 (Series A) is D, 1, 2 and 3.

Fly ash, the fine fraction of coal ash, has a well-established reuse market backed by mandatory-use notifications since 1999.

Coal-fired power plants release sulphur dioxide and oxides of nitrogen during combustion, separate from the solid ash they produce.

Coal ash contains arsenic, lead, and mercury, along with other trace metals, all naturally present in the original coal.

Indian coal typically has 25 to 45 percent ash content, notably higher than imported coal’s 10 to 20 percent.

Coal ash genuinely contains these heavy metals, coal plants do release SO2 and NOx, and Indian coal genuinely has high ash content. All three are correct.

The CGWA was constituted in January 1997, under Section 3(3) of the Environment (Protection) Act, 1986, following a Supreme Court direction.

The Environment (Protection) Act, 1986 was enacted as a direct legislative response to the 1984 Bhopal Gas Tragedy, India’s worst industrial disaster.