Announcement
Pollution/Ozone-Day 12
Assertion (A): Ocean acidification significantly impairs the ability of marine organisms like corals and mollusks to build and maintain their shells.
Reason (R): An increase in the absorption of atmospheric carbon dioxide by the oceans leads to a decrease in the concentration of carbonate ions in the water.
- A A is true, but R is false.
- B Both A and R are true, and R is the correct explanation of A.
- C Both A and R are true, but R is NOT the correct explanation of A.
- D A is false, but R is true.
Explanation: Both A and R are true, and R is the correct explanation. When oceans absorb excess CO2, it forms carbonic acid, which releases hydrogen ions. These hydrogen ions bond with free carbonate ions in the water to form bicarbonate. Because corals and mollusks rely on free carbonate ions to build calcium carbonate shells, this depletion (ocean acidification) directly impairs their survival.
Assertion (A): The deposition of black carbon (soot) on the Himalayan glaciers accelerates their melting process.
Reason (R): Black carbon increases the surface albedo of the snow and ice, causing them to absorb more solar radiation.
- A A is true, but R is false.
- B A is false, but R is true.
- C Both A and R are true, and R is the correct explanation of A.
- D Both A and R are true, but R is NOT the correct explanation of A.
Explanation: Assertion is true, but Reason is false. Black carbon (soot) does accelerate the melting of glaciers, but it does so by decreasing the albedo (reflectivity) of the ice, not increasing it. Dark soot absorbs more solar radiation, warming the surrounding ice.
Assertion (A): Photochemical smog is primarily a winter phenomenon occurring in cold, damp, and cloudy climates.
Reason (R): Volatile Organic Compounds (VOCs) and Nitrogen Oxides (NOx) react in the presence of sunlight to form ground-level ozone.
- A Both A and R are true, and R is the correct explanation of A.
- B A is true, but R is false.
- C A is false, but R is true.
- D Both A and R are true, but R is NOT the correct explanation of A.
Explanation: Assertion is false, but Reason is true. Photochemical smog is a summer phenomenon (often called Los Angeles smog) that requires warm, dry, and sunny climates to occur. It forms precisely because UV sunlight drives the reaction between VOCs and NOx to create secondary pollutants like ozone.
Assertion (A): The thawing of Arctic permafrost acts as a severe positive feedback loop for global warming.
Reason (R): Thawing permafrost releases large quantities of previously trapped methane and carbon dioxide into the atmosphere.
- A Both A and R are true, but R is NOT the correct explanation of A.
- B A is false, but R is true.
- C A is true, but R is false.
- D Both A and R are true, and R is the correct explanation of A.
Explanation: Both A and R are true, and R explains A. Permafrost holds vast amounts of ancient organic matter. When it thaws, microbes decompose this matter, releasing potent greenhouse gases (Methane and CO2). This warming causes more permafrost to thaw, creating a dangerous positive feedback loop.
Assertion (A): Acid rain can lead to the widespread death of fish in lakes and streams.
Reason (R): Acid rain lowers the pH of water bodies and leaches toxic metals like aluminum from the surrounding soil into the water.
- A Both A and R are true, and R is the correct explanation of A.
- B Both A and R are true, but R is NOT the correct explanation of A.
- C A is true, but R is false.
- D A is false, but R is true.
Explanation: Both A and R are true, and R explains A. Acid rain lowers the pH of lakes, which directly stresses fish. More severely, acidic water leaches toxic aluminum from the soil into aquatic ecosystems. This aluminum damages the gills of fish, suffocating them, explaining the widespread aquatic deaths.
Assertion (A): Apex predators, such as eagles and polar bears, are highly susceptible to the effects of Persistent Organic Pollutants (POPs) like DDT.
Reason (R): POPs are water-soluble compounds that are easily excreted by organisms at lower trophic levels.
- A Both A and R are true, and R is the correct explanation of A.
- B A is true, but R is false.
- C A is false, but R is true.
- D Both A and R are true, but R is NOT the correct explanation of A.
Explanation: Assertion is true, but Reason is false. Apex predators are highly susceptible due to biomagnification. However, POPs are fat-soluble (lipophilic), not water-soluble. Because they dissolve in fat, they are not easily excreted, which is why they accumulate in tissues and magnify up the food chain.
Assertion (A): The ozone hole over Antarctica is most prominent during the Antarctic spring (September to November).
Reason (R): Polar Stratospheric Clouds (PSCs), which facilitate ozone-depleting catalytic reactions, form during the extremely cold Antarctic winter.
- A A is true, but R is false.
- B Both A and R are true, but R is NOT the correct explanation of A.
- C Both A and R are true, and R is the correct explanation of A.
- D A is false, but R is true.
Explanation: Both A and R are true, and R explains A. During the ultra-cold Antarctic winter, Polar Stratospheric Clouds (PSCs) form. These clouds provide a surface for inactive chlorine compounds to convert into ozone-destroying forms. When the sun returns in the spring (Sept-Nov), the UV light acts on these compounds, rapidly depleting the ozone layer.
Assertion (A): Mangrove ecosystems are highly effective at sequestering "Blue Carbon" compared to many terrestrial forests.
Reason (R): Mangrove soils are highly oxygenated (aerobic), which promotes the rapid decomposition and stabilization of organic matter.
- A Both A and R are true, and R is the correct explanation of A.
- B A is false, but R is true.
- C A is true, but R is false.
- D Both A and R are true, but R is NOT the correct explanation of A.
Explanation: Assertion is true, but Reason is false. Mangroves are excellent carbon sinks (Blue Carbon). However, their soils are highly anaerobic (lacking oxygen) because they are waterlogged. This lack of oxygen slows down decomposition, allowing massive amounts of organic carbon to be stored in the soil for millennia.
Assertion (A): The Kigali Amendment to the Montreal Protocol mandates the phase-down of Hydrofluorocarbons (HFCs).
Reason (R): Hydrofluorocarbons (HFCs) are potent ozone-depleting substances that severely damage the stratospheric ozone layer.
- A A is true, but R is false.
- B Both A and R are true, and R is the correct explanation of A.
- C A is false, but R is true.
- D Both A and R are true, but R is NOT the correct explanation of A.
Explanation: Assertion is true, but Reason is false. The Kigali Amendment does mandate the phase-down of HFCs. However, HFCs are not ozone-depleting substances (they were actually introduced to replace ODS like CFCs). They are being phased down because they are extraordinarily potent greenhouse gases that drive global warming.
Assertion (A): Eutrophication leads to the formation of hypoxic "dead zones" in coastal marine ecosystems.
Reason (R): Excessive nutrient runoff promotes sudden algal blooms, and the subsequent bacterial decomposition of these dead algae depletes dissolved oxygen in the water.
- A Both A and R are true, but R is NOT the correct explanation of A.
- B Both A and R are true, and R is the correct explanation of A.
- C A is true, but R is false.
- D A is false, but R is true.
Explanation: Both A and R are true, and R explains A. Agricultural runoff causes an explosion of algal growth. When these algae die, massive amounts of aerobic bacteria consume them. The bacteria use up the dissolved oxygen in the water, creating a hypoxic environment (dead zone) where marine life cannot survive.
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