Match the items given in Column-I and Column-II: Column-I A. Biomagnification B. Electro-precipitation C. Landfills D. Stratosphere Column-II 1. Synthesis of ozone 2. Solid waste 3. Concentration build-up at successive trophic levels 4. Particulate matter Codes:
- (a)A-3, B-4, C-2, D-1
- (b)A-1, B-2, C-3, D-4
- (c)A-2, B-1, C-4, D-3
- (d)A-4, B-3, C-1, D-2
Correct — A, A-3, B-4, C-2, D-1.
Biomagnification is defined as the rise in a persistent substance's concentration at each higher feeding level, which is what Column-II states at 3. Electro-precipitation names the electrostatic precipitator, a stack device that charges suspended particles and draws them onto collecting plates, so B takes 4.
Landfills are where municipal solid waste is finally deposited, giving C-2. Ozone is synthesised in the stratosphere when solar ultraviolet splits molecular oxygen and the freed atoms join other oxygen molecules, giving D-1.
The code carrying all four is A-3, B-4, C-2, D-1.
Carry away that each Column-II entry names the process, medium or product by which its Column-I term is defined — so fix the one pairing you are surest of and delete every code that contradicts it.
- (b)A-1, B-2, C-3, D-4 — This is the code you get by reading the two columns straight down the page — A with 1, B with 2, C with 3, D with 4. Column-II is printed in a different sequence from Column-I, so the serial reading misplaces each item.
Synthesis of ozone (1) is the correct partner for the stratosphere, which is D in Column-I, not A. Solid waste (2) belongs to landfills rather than to a flue-gas cleaning device.
- (c)A-2, B-1, C-4, D-3 — Solid waste (2) is the material a landfill receives, so 2 answers Landfills, which is C. Handing it to biomagnification loses the definition that Column-II already states plainly at 3.
This code also sends ozone synthesis to electro-precipitation. An electrostatic precipitator works on charged solid particles carried in a gas stream, not on the photochemistry of the upper atmosphere.
- (d)A-4, B-3, C-1, D-2 — Concentration build-up at successive trophic levels (3) is the textbook definition of biomagnification, so 3 belongs at A. Here it is given to electro-precipitation, which names a particle-collecting device rather than a food-chain process.
The code then leaves landfills paired with ozone synthesis and the stratosphere paired with solid waste, reversing the two pairings that the terms themselves settle.
Four separate ideas sit in this set, one behind each Column-I entry.
Biomagnification is ecological: a persistent, fat-soluble substance that an organism cannot readily excrete passes intact to whatever eats it, so its tissue concentration climbs at each higher trophic level. It is distinct from bioaccumulation, which is build-up within a single organism over its lifetime.
Electro-precipitation is engineering: an electrostatic precipitator gives suspended particles in a flue gas an electric charge and collects them on oppositely charged plates, from which they are shaken off.
Landfilling is the disposal end of solid waste management, where residual waste is deposited in an engineered site. The stratosphere is the atmospheric layer in which ozone is manufactured from oxygen by solar ultraviolet radiation.
The item spans four corners of the environment syllabus at once — ecology, pollution-control technology, waste management and atmospheric science — and asks only that each term be held with its defining idea.
Each Column-II phrase is a standard description of one specific term, so the pairing is settled by definitions rather than judgement. That structure makes the whole code recoverable from a single certain pair plus elimination, even when one of the four terms is unfamiliar.
- Biomagnification is the increase in the concentration of a persistent substance at each successive trophic level of a food chain.
- Bioaccumulation is the build-up of a substance within one organism over its lifetime, and is a different idea from biomagnification.
- DDT, polychlorinated biphenyls and methylmercury are standard textbook examples of substances that biomagnify.
- An electrostatic precipitator charges particles in a flue gas and collects them on oppositely charged plates; it is fitted on thermal power plant and cement kiln stacks.
- Electrostatic precipitators target particulate matter, while sulphur dioxide in flue gas is handled separately by flue gas desulphurisation.
- A sanitary landfill is an engineered disposal site for solid waste, and generates leachate along with a methane-rich landfill gas.
- Roughly ninety per cent of atmospheric ozone lies in the stratosphere, with the peak number density around 20-25 km, varying with latitude.
- Stratospheric ozone forms when short-wave ultraviolet splits an oxygen molecule and the freed oxygen atoms combine with other oxygen molecules.
- Ozone also occurs near the ground as a secondary pollutant formed from oxides of nitrogen and volatile organic compounds in sunlight.
The keyed code, A-3, B-4, C-2, D-1. Reading the two printed columns straight down instead gives the code in option (b).
- Electro-precipitation reads like a liquid or chemical treatment; the device it names cleans a gas stream of suspended solid particles, which is what ties it to particulate matter.
- Ozone occurs at ground level as a pollutant too, so the word alone does not fix the layer — only the synthesis step does.
- Biomagnification and bioaccumulation are separate terms, and it is biomagnification that is defined across successive trophic levels.
- A matching set is scored whole: three right pairings earn nothing if the fourth is misplaced, so verify the full code rather than the pair you spotted first.
- Pairing the columns in their printed order is a shortcut that only works when the paper happens to print them in step, and here it does not.
These ideas also recur one at a time. UPPSC 2023 asked the definition of a trophic level directly.
CAPF 2024 and CDS 2021-II asked why a food chain stays short, which turns on the energy lost at each level. ESE 2023 and Geologist 2024 took the same stratospheric ozone into depletion and its chemistry.
In a matching set they are paired with the process, medium or product that defines the term. Once each definition can be stated in a single clause, the code follows by eliminating whichever option contradicts your surest pair.
Descriptive papers take the same material and ask for the sources of a pollutant to be explained in prose.
UKPSC_2024_MAINS_GSIII_Q32024Same commission and the same pollutant category as the B-4 pairing here — particulate matter. What differs is the direction and the format: the Mains item asks for the sources of particulate matter to be listed and explained in prose, while this Prelims item asks only that the pollutant be linked to the device that removes it. Read together, they cover both ends of the same topic, where the material comes from and how it is captured.
ESE_GS_2023_Q982023Shares the D-1 pairing's subject, ozone in the stratosphere. What differs is the process being tested: the ESE statement pair is about depletion and the resulting loss of ultraviolet filtering, whereas this item is about synthesis, the step by which stratospheric ozone is formed in the first place. Holding both keeps formation and destruction apart in the same layer.
UPPSC_2023_PRE_GSI_Q1172023Same vocabulary as descriptor 3, trophic levels, and answered from the same definition that organisms linked in a food chain form them. What differs is the depth asked: UPPSC turns on the definition of a trophic level itself, while UKPSC assumes it and tests what happens to a persistent substance as it moves up those levels.
CAPF_GAI_2024_Q292024Also built on the trophic ladder, but tested through energy rather than through toxicants: it turns on the loss of energy at each level as the reason food chains stay short. What differs is the quantity being tracked up the chain — energy falls at each step, while a biomagnifying substance concentrates. The two make a useful contrast on the same structure.
- practice — not a real PYQ
Which device removes suspended particles from an industrial flue gas by imparting an electric charge to them and collecting them on oppositely charged plates?
- (a)Cyclone separator
- (b)Electrostatic precipitator
- (c)Catalytic converter
- (d)Flue gas desulphurisation unit
Answerb — the mechanism named in the stem, charging the particles and collecting them on plates, is the defining action of an electrostatic precipitator.(a) fails because a cyclone separates particles by centrifugal force in a spinning gas stream, without charging them.
(c) fails because a catalytic converter treats gaseous exhaust species such as carbon monoxide, hydrocarbons and oxides of nitrogen. (d) fails because flue gas desulphurisation is aimed at sulphur dioxide, a gas, rather than at particulate matter.
- practice — not a real PYQ
A persistent, fat-soluble pesticide is present in trace amounts in pond water but is found at far higher concentrations in the tissues of fish-eating birds of that pond. This progressive rise along the food chain is called:
- (a)Bioaccumulation
- (b)Eutrophication
- (c)Biomagnification
- (d)Bioremediation
Answerc — biomagnification is precisely the increase in the concentration of a persistent substance at each successive trophic level, which is what the movement from water to fish-eating bird describes.(a) fails because bioaccumulation refers to build-up within a single organism over its lifetime, rather than to the rise across feeding levels.
(b) fails because eutrophication is nutrient enrichment of a water body leading to algal growth and oxygen depletion. (d) fails because bioremediation is the use of organisms to degrade or remove contaminants.
- practice — not a real PYQ
Ozone in the stratosphere is produced when:
- (a)oxides of nitrogen react with volatile organic compounds in sunlight near the ground
- (b)chlorofluorocarbons release chlorine atoms that combine with molecular oxygen
- (c)carbon dioxide is dissociated by infrared radiation
- (d)short-wave ultraviolet radiation splits molecular oxygen and the freed atoms combine with other oxygen molecules
Answerd — this is the formation step of stratospheric ozone: ultraviolet photolysis of oxygen gives atomic oxygen, which then joins an oxygen molecule to make ozone.(a) fails because it describes the photochemical formation of ozone at ground level, which the stem excludes by specifying the stratosphere.
(b) fails because chlorine released from chlorofluorocarbons destroys stratospheric ozone rather than producing it. (c) fails because ozone is built from oxygen, and infrared radiation excites carbon dioxide molecules rather than dissociating them.
- practice — not a real PYQ
The anaerobic decomposition of the organic fraction of municipal solid waste in a landfill chiefly generates:
- (a)Sulphur dioxide and chlorine
- (b)Methane and carbon dioxide
- (c)Ozone and nitrogen dioxide
- (d)Carbon monoxide and sulphur trioxide
Answerb — landfill gas is dominated by methane and carbon dioxide, produced as micro-organisms break down the organic fraction in the absence of oxygen. This is why landfill gas is collected and, at many sites, burned for energy.(a) and (d) fail because sulphur oxides and chlorine are associated with combustion and industrial processes rather than with anaerobic decay. (c) fails because ozone and nitrogen dioxide are atmospheric species linked to photochemistry and high-temperature combustion, not to decomposition in a buried waste mass.