Daily Static Quiz Prelims Practice 2027
Option (b) is correct — PM2.5 (≤2.5 µm) penetrates deep into the alveoli and crosses into the bloodstream, causing systemic effects like cardiovascular disease, stroke, and low birth weight, beyond respiratory damage alone. Option (a) is wrong — the hazard is reversed; PM2.5 is more dangerous precisely due to its smaller size and deeper penetration, not PM10. Option (c) is wrong — NAAQS sets different annual mean limits for PM10 (60 µg/m³) and PM2.5 (40 µg/m³), not identical ones. Option (d) is wrong — the definitions are reversed; primary pollutants are directly emitted (like vehicle soot), while secondary pollutants form through atmospheric chemical reactions.
- BOD measures the amount of dissolved oxygen consumed by microorganisms while decomposing organic matter in a water sample over five days at 20°C.
- A high BOD value indicates low organic pollution and good water quality suitable for drinking.
- The Central Pollution Control Board classifies rivers into five categories (A to E) based on designated best use, with Class A being the most stringent and associated with drinking water after conventional treatment.
- Eutrophication leads to a reduction in BOD over time because algal photosynthesis continuously replenishes dissolved oxygen in the water body.
Statements 1 and 3 are correct. BOD₅ is measured by incubating a water sample at 20°C for five days and measuring dissolved oxygen consumed, the standard CPCB method. CPCB classifies rivers from Class A (drinking water with conventional treatment and disinfection) to Class E (irrigation, industrial cooling). Statement 2 is incorrect — a high BOD actually indicates high organic pollution and poor water quality, the opposite of what's stated. Statement 4 is incorrect — eutrophication increases BOD over time, since decomposing algal blooms consume large amounts of dissolved oxygen, worsening rather than reducing BOD.
Option (b) is correct — tropospheric ozone is a secondary pollutant forming when NOx (from vehicles and industrial combustion) reacts with VOCs (from vehicles, solvents, vegetation) in sunlight, the defining photochemical smog mechanism peaking on hot, sunny, low-wind days. Option (a) is wrong — refineries emit VOCs and NOx, the precursors, not ozone itself. Option (c) is wrong — natural stratosphere-to-troposphere transport occurs, but doesn't dominate elevated urban ozone, where anthropogenic photochemical production is the primary driver. Option (d) is wrong — sulphur-rich coal combustion primarily emits SO₂ and particulate matter, not ozone.
- Phytoremediation uses hyperaccumulator plants to absorb heavy metals from contaminated soil, with species like Pteris vittata used for arsenic and Thlaspi caerulescens for zinc and cadmium.
- Bioremediation uses microorganisms to degrade or immobilise organic pollutants such as petroleum hydrocarbons and pesticide residues in soil.
- The accumulation of persistent organic pollutants (POPs) such as DDT in soil is a concern primarily because they degrade rapidly through solar radiation, releasing toxic breakdown products.
- Cadmium contamination of agricultural soil is associated with the use of phosphate fertilisers, as phosphate rock deposits naturally contain cadmium as an impurity.
Statements 1, 2 and 4 are correct. Pteris vittata hyperaccumulates arsenic and Thlaspi caerulescens accumulates zinc and cadmium, both used in phytoremediation. Bioremediation exploits microbial pathways to break down petroleum hydrocarbons, chlorinated solvents, and pesticide residues. Phosphate rock used in fertiliser manufacturing naturally contains cadmium, and long-term use gradually elevates soil cadmium, entering the food chain. Statement 3 is incorrect — POPs like DDT are concerning precisely because they resist rapid degradation, persisting for years or decades due to their chemical stability and lipid solubility, leading to biomagnification, not rapid solar breakdown.
- 1. Ozone-depleting substances — Montreal Protocol / Environment Protection Act
- 2. Hazardous wastes — Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016
- 3. Noise from industrial sources — Water (Prevention and Control of Pollution) Act, 1974
- 4. Plastic waste — Plastic Waste Management Rules, 2016
Pairs 1, 2 and 4 are correctly matched. India implements the Montreal Protocol on ozone-depleting substances through the Environment (Protection) Act, 1986. Hazardous wastes are governed by the Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016, aligned with the Basel Convention. Plastic waste is governed by the Plastic Waste Management Rules, 2016 (amended 2018, 2021), including extended producer responsibility. Pair 3 is incorrect — industrial noise is regulated under the Noise Pollution (Regulation and Control) Rules, 2000, not the Water Act, 1974, which governs water pollution and discharge standards instead.
