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Q90 (IAS/2024) Environment & Ecology › Pollution & Conservation › Air pollution and health Official Key

According to the Environmental Protection Agency (EPA), which one of the following is the largest source of sulphur dioxide emissions ?

Result
Your answer: —  ·  Correct: D
Explanation

The largest sources of SO2 emissions are from fossil fuel combustion at power plants and other industrial facilities.[5] This is clearly stated by the EPA across multiple references. In contrast, locomotives, ships and other vehicles and heavy equipment that burn fuel with a high sulfur content are classified as smaller sources of SO2 emissions.[2] Additionally, over 97% of the man-made sources are stationary, except for transportation sources (which include motor vehicles, vessels, and railroads).[7] This confirms that power plants, being major stationary sources using fossil fuels, are the largest contributors to sulfur dioxide emissions. Therefore, option D - Power plants using fossil fuels - is the correct answer according to the EPA.

Sources
  1. [1] https://www.epa.gov/so2-pollution/sulfur-dioxide-basics
  2. [2] https://www.epa.gov/so2-pollution/sulfur-dioxide-basics
  3. [3] https://documents1.worldbank.org/curated/en/099032625132535486/pdf/P502230-d16d0858-2e18-41df-a7a6-f1188121ac83.pdf
  4. [4] https://www.epa.gov/so2-pollution/sulfur-dioxide-basics
  5. [5] https://documents1.worldbank.org/curated/en/099032625132535486/pdf/P502230-d16d0858-2e18-41df-a7a6-f1188121ac83.pdf
  6. [6] https://documents1.worldbank.org/curated/en/813211468331794803/pdf/multi0page.pdf
  7. [7] https://documents1.worldbank.org/curated/en/813211468331794803/pdf/multi0page.pdf
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Q. According to the Environmental Protection Agency (EPA), which one of the following is the largest source of sulphur dioxide emissions ? …
At a glance
Origin: Mostly Current Affairs Fairness: Low / Borderline fairness Books / CA: 0/10 · 10/10

This is a 'Sitter' disguised as a 'Bouncer'. The tag 'According to EPA' is an intimidation tactic to make you think you missed a specific report. In reality, the answer relies on the most fundamental static fact of Environmental Science: Coal-fired power plants are the primary global source of SO2. Trust your basic NCERT/Shankar knowledge over the fear of missing a specific report.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
According to the U.S. Environmental Protection Agency (EPA), are locomotives using fossil fuels the largest source of sulfur dioxide (SO2) emissions?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"The largest sources of SO2 emissions are from fossil fuel combustion at power plants and other industrial facilities. Smaller sources of SO2 emissions include: ... locomotives, ships and other vehicles and heavy equipment that burn fuel with a high sulfur content."
Why this source?
  • This EPA page explicitly states the largest SO2 sources are fossil fuel combustion at power plants and other industrial facilities.
  • It then lists locomotives among 'smaller sources', showing locomotives are not the largest source per the EPA.
Web source
Presence: 4/5
"utilize coal and oils as fuel, are the leading sources of sulfur dioxide emissions. Except for transportation sources (which include motor vehicles, vessels, and railroads), over 97% of the man-made sources are stationary."
Why this source?
  • States that sources which utilize coal and oil are the leading sources of sulfur dioxide emissions (i.e., stationary power/industrial sources).
  • Notes transportation (including railroads) is a small fraction and that over 97% of man-made sources are stationary, implying locomotives are not the largest source.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Acidification > p. 8
Strength: 5/5
“motor vehicles inject large amounts of these chemicals into the atmosphere. In the atmosphere, the chemicals combine with water to form sulphuric acid and nitric acid. Tese droplets may be transported at great distances by wind before they precipitate to the ground (Fig. 6.1). Te main gases involved in the production of acid rains are nitrogen oxides—sulphur dioxide (SO2), nitrogen dioxide (NO2) and nitrous oxide (NO). Te major sources of these gases is due to burning of fossil fuel and industrial processes. Acid rain is a phrase that applies to a process that results in deposition of acid on the surface of the Earth.”
Why relevant

States that sulphur dioxide (SO2) is one of the main gases producing acid rain and that the major sources are burning of fossil fuel and industrial processes.

How to extend

A student could use this general rule plus sector-level SO2 data (e.g., power plants vs. transportation) to judge whether locomotives (a transportation sub‑sector) are likely the largest source.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > The main sources > p. 256
Strength: 4/5
“• i. The combustion of fossil fuels to generate electricity. • ii. The combustion of fossil fuels such as gasoline and diesel used for transportation. • iii. Many industrial processes emit CO e through fossil fuel combustion. • iv. Several processes also produce CO e emissions through chemical reactions that do not involve combustion, for example, the production and consumption of mineral products such as cement, the production of metals such as iron and steel, and the production of chemicals, etc.”
Why relevant

Lists combustion of fossil fuels for electricity and for transportation as main sources of emissions, implying transportation is a contributor but separate from electricity/industry.

How to extend

Compare relative emissions of the electricity sector (thermal power) and the transportation sector to see if the transport subsector 'locomotives' could dominate national SO2 emissions.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 6: Geomorphic Movements > Anthropogenic Solution Weathering > p. 91
Strength: 4/5
“• Rainfall is naturally acidic ― pH of ~5.6 (CO2 dissolves in the rainwater producing weak carbonic acid). • Sulphur dioxide, SO2, comes from volcanic eruptions or fossil fuels. The conversion of metallic ores to pure metals often results in the formation of sulphur dioxide.”
Why relevant

Specifies SO2 originates from volcanic eruptions or fossil fuels and notes metal production can form SO2, indicating multiple large non‑transport sources.

How to extend

Use this to suspect that industrial processes and power generation (fossil fuel combustion) are important SO2 sources that may exceed locomotive emissions.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Measures to Check Efects of Acidic Precipitation > p. 10
Strength: 4/5
“Both in the developed and developing countries various remedial measures have been taken to reduce the adverse afect of acidic precipitation. Some of the remedial steps are: • (i) Curtailing the emission of harmful gases and substances from the thermal and other chemical plants.• (ii) Compelling the industries to use better quality of coal which has low emission level of sulphur and other harmful substances.• (iii) Using alternate technologies for efcient use of fossil fuels.• (iv) Implementation of the environmental pollution laws more efectively.• (v) Environmental Impact Assessment on plants, animals, humanity and ecology before the establishment of any major or minor industry.• (vi) Public awareness about acidic rain and its impact on economy, society and ecology.”
Why relevant

Remedial measures emphasise curtailing emissions from thermal and other chemical plants and using low‑sulfur coal, implying thermal power and industry are priority SO2 sources.

How to extend

A student could infer that if policy targets thermal/industrial sources, those sectors likely contribute more SO2 than individual transport modes like locomotives.

Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 12: Transport, Communications and Trade > Main Features of Indian Railways > p. 12
Strength: 3/5
“Prior to Independence, the whole railways system was under steam traction. Since it had poor efficiency and caused great environmental pollution the diesel engines were introduced in 1950s. At present, Diesel Locomotive Works (DLW), Varanasi (UP), Chitranjan Locomotive Works (West Bengal), and Mihijam and Tat Engineering and Locomotive Works, Jamshedpur (Jharkhand), are producing diesel engines for railways. The diesel engines were also the cause of environmental pollution; therefore, in order to overcome the pollution problem and to cope with the growing pressure of traffic and goods, a decision was taken to switch over to electric traction all the important routes.”
Why relevant

Notes diesel locomotives were introduced and caused environmental pollution, later shifted to electric traction to reduce pollution—showing locomotives are a known source of emissions but not quantifying scale.

How to extend

Combine this with knowledge of fleet size/fuel use to estimate locomotive SO2 emissions and compare with larger stationary sources to assess relative rankings.

Statement 2
According to the U.S. Environmental Protection Agency (EPA), are ships using fossil fuels the largest source of sulfur dioxide (SO2) emissions?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"The largest sources of SO2 emissions are from fossil fuel combustion at power plants andother industrial facilities. Smaller sources of SO2 emissions include: ... locomotives, ships and other vehicles and heavy equipment that burn fuel with a high sulfur content."
Why this source?
  • This is an EPA source that explicitly identifies the largest sources of SO2.
  • It states that power plants and other industrial facilities burning fossil fuels are the largest sources and lists ships as a smaller source.
Web source
Presence: 4/5
"utilize coal and oils as fuel, are the leading sources of sulfur dioxide emissions, as shcwn above. Except for transportation sources (which include motor vehicles, vessels, and railroads), over 97% of the man-made sources are stationary."
Why this source?
  • Notes that coal- and oil-using (stationary) sources are the leading sources of SO2.
  • Specifies that transportation sources (which include vessels/ships) are a small portion of man-made SO2 sources (over 97% are stationary).
Web source
Presence: 4/5
"The major source is from the ccmbustion of fossil fuels such as coal and oil. Sane 90 to 95 percent of pollution-related sulfur oxide emissions are in the form of sulfur diox-ide."
Why this source?
  • Identifies combustion of fossil fuels (coal and oil) as the major source of SO2.
  • Establishes that most sulfur oxide emissions are SO2, supporting that large stationary fossil-fuel sources dominate total SO2 emissions.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > a) Sulphur > p. 102
Strength: 5/5
“(a) Sulphur '.ilU-/ rz j! U • (i) Natural sources: • seas and oceans, • r volcanic eruptions, • r Biological processes in the soil 8.9., Decomposition of organic matter. • (ii) Man-made sources: • r burning of coal (6o0/o of SO,), and • . petroleum products $oolr of SO,), and • r The smelting of metal sulfide ores to obtain the pure metals. • e Industrial production of Sulfuric atid in metallurgical, chemical and fertilizer industries. • (b) Nitrogen Natural sources: • r lightenin&• r volcanic eruption, and• r Biological activity.”
Why relevant

Gives a quantitative breakdown of SO2 man-made sources: burning of coal (~60%) and petroleum products (~30%) are listed as the main anthropogenic sources.

How to extend

A student could combine this with the fact that ships burn petroleum-based marine fuels to judge whether shipping could form a substantial fraction of the 'petroleum products' share and thus test if it could be the largest single source.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Acidification > p. 8
Strength: 4/5
“motor vehicles inject large amounts of these chemicals into the atmosphere. In the atmosphere, the chemicals combine with water to form sulphuric acid and nitric acid. Tese droplets may be transported at great distances by wind before they precipitate to the ground (Fig. 6.1). Te main gases involved in the production of acid rains are nitrogen oxides—sulphur dioxide (SO2), nitrogen dioxide (NO2) and nitrous oxide (NO). Te major sources of these gases is due to burning of fossil fuel and industrial processes. Acid rain is a phrase that applies to a process that results in deposition of acid on the surface of the Earth.”
Why relevant

States that the main gases (including SO2) arise from burning of fossil fuel and industrial processes, establishing fossil-fuel combustion as a primary SO2 source.

How to extend

Use knowledge of major fossil-fuel consumers (power plants, industry, transport including shipping) to compare relative contributions and evaluate shipping's potential rank.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > The main sources > p. 256
Strength: 4/5
“• i. The combustion of fossil fuels to generate electricity. • ii. The combustion of fossil fuels such as gasoline and diesel used for transportation. • iii. Many industrial processes emit CO e through fossil fuel combustion. • iv. Several processes also produce CO e emissions through chemical reactions that do not involve combustion, for example, the production and consumption of mineral products such as cement, the production of metals such as iron and steel, and the production of chemicals, etc.”
Why relevant

Lists combustion of fossil fuels for electricity generation, transportation, and industry as main sources of emissions, implying transport (which includes shipping) is a recognized SO2-related sector.

How to extend

A student could obtain basic external data on how much petroleum-based fuel shipping consumes relative to other transport sub-sectors to assess if it could be the single largest SO2 source.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 6: Geomorphic Movements > Anthropogenic Solution Weathering > p. 91
Strength: 3/5
“• Rainfall is naturally acidic ― pH of ~5.6 (CO2 dissolves in the rainwater producing weak carbonic acid). • Sulphur dioxide, SO2, comes from volcanic eruptions or fossil fuels. The conversion of metallic ores to pure metals often results in the formation of sulphur dioxide.”
Why relevant

Notes that SO2 comes from volcanic eruptions or fossil fuels, highlighting the split between natural and anthropogenic SO2 sources.

How to extend

Combine this with geographic/sectoral SO2 inventories (natural vs human) to determine whether anthropogenic sources dominate and whether shipping might top the anthropogenic list.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Sources of Marine Pollution > p. 46
Strength: 2/5
“• 4. Sewage Disposal into the Seas and Oceans: Normally, the greatest volume of waste discharged into the sea is sewage. It is one of the biggest marine pollutant. Te sources of oil pollution have been given in Table 6.1.• 5. Volcanic Eruptions: Volcanic eruptions add enormous quantities carbon dioxides, methan, sulphur compounds, etc. into the oceans.• 6. Cosmic dust: Meteors and cosmic dust from the space fall into the oceans known as taktites. Tis is also an important source of marine pollution. • Source of oil pollution: 1. Use and disposal; Percentage: 34% • Source of oil pollution: 2.”
Why relevant

Mentions volcanic eruptions add sulphur compounds (a natural SO2 source), providing a counterpoint to fossil-fuel sources and indicating multiple source categories to compare.

How to extend

A student could use basic external facts (e.g., locations and frequency of volcanic emissions vs. global fuel combustion patterns) to estimate relative shares and see if shipping plausibly exceeds other fossil-fuel sources.

Statement 3
According to the U.S. Environmental Protection Agency (EPA), is extraction of metals from ores the largest source of sulfur dioxide (SO2) emissions?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"The largest sources of SO2 emissions are from fossil fuel combustion at power plants and other industrial facilities."
Why this source?
  • Explicitly identifies the largest sources of SO2 emissions as fossil fuel combustion at power plants and other industrial facilities.
  • Directly contradicts the idea that metal extraction from ores is the largest source.
Web source
Presence: 4/5
"The major source is from the combustion of fossil fuels such as coal and oil. Sane 90 to 95 percent of pollution-related sulfur oxide emissions are in the form of sulfur diox-ide."
Why this source?
  • States the major source of man-made SO2 emissions is combustion of fossil fuels such as coal and oil.
  • Notes that 90 to 95 percent of pollution-related sulfur oxide emissions are in the form of sulfur dioxide, reinforcing combustion as the dominant source.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > a) Sulphur > p. 102
Strength: 5/5
“(a) Sulphur '.ilU-/ rz j! U • (i) Natural sources: • seas and oceans, • r volcanic eruptions, • r Biological processes in the soil 8.9., Decomposition of organic matter. • (ii) Man-made sources: • r burning of coal (6o0/o of SO,), and • . petroleum products $oolr of SO,), and • r The smelting of metal sulfide ores to obtain the pure metals. • e Industrial production of Sulfuric atid in metallurgical, chemical and fertilizer industries. • (b) Nitrogen Natural sources: • r lightenin&• r volcanic eruption, and• r Biological activity.”
Why relevant

Explicitly lists man-made sources of SO2 and names 'the smelting of metal sulfide ores to obtain the pure metals' as one source, while also calling out burning of coal and petroleum products as major sources.

How to extend

A student could treat this as a ranked list cue and check EPA emissions inventories to compare the relative contribution of smelting versus combustion (coal/petroleum) to see which is largest.

Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.4.4 Extracting Metals in the Middle of the Activity Series > p. 51
Strength: 4/5
“The metals in the middle of the activity series such as iron, zinc, lead, copper, are moderately reactive. These are usually present as sulphides or carbonates in nature. It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonates. Therefore, prior to reduction, the metal sulphides and carbonates must be converted into metal oxides. The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting. The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination.”
Why relevant

Describes that sulphide ores are converted to oxides by roasting in presence of excess air — a metallurgical step that typically releases sulfur compounds (e.g., SO2).

How to extend

Use this process-link to identify industrial facilities (roasters/smelters) on a map and compare their emissions footprints with other industrial sources reported by EPA.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > 20.1. Composition of The Earth's Atmosphere > p. 270
Strength: 3/5
“• The composition of Earth's atmosphere is largely governed by the by-products of the life it sustains. Dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon and traces of hydrogen, helium, and other noble gases. The remaining gases are often referred to as trace gases, among which are the greenhouse gases, principally carbon dioxide (0.036%), methane, nitrous oxide, and ozone.• Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds and elemental mercury vapour. Sulphur compounds such as hydrogen sulphide (H2S) and sulphur dioxide (SO2) may be derived from natural sources or industrial air pollution.”
Why relevant

Notes that sulfur compounds such as SO2 can derive from natural sources or industrial air pollution, framing SO2 as both geogenic and anthropogenic with multiple industrial contributors.

How to extend

Combine this general source-categorization with EPA sectoral emissions data (power generation, transport, metallurgy) to judge which sector dominates SO2 emissions.

Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > What you have learnt > p. 55
Strength: 2/5
“These oxides are known as amphoteric oxides.• n Different metals have different reactivities with water and dilute acids.• n A list of common metals arranged in order of their decreasing reactivity is known as an activity series.• n Metals above hydrogen in the Activity series can displace hydrogen from dilute acids.• n A more reactive metal displaces a less reactive metal from its salt solution.• n Metals occur in nature as free elements or in the form of their compounds.• n The extraction of metals from their ores and then refining them for use is known as metallurgy.• n An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.• n The surface of some metals, such as iron, is corroded when they are exposed to moist air for a long period of time.”
Why relevant

Defines the extraction of metals from ores as 'metallurgy', linking the activity in the statement to a named industrial category that could be compared in emissions inventories.

How to extend

Search EPA terminology or inventories for 'metallurgy'/'metal extraction' emissions entries and compare reported SO2 quantities to other sectors.

Statement 4
According to the U.S. Environmental Protection Agency (EPA), are power plants using fossil fuels the largest source of sulfur dioxide (SO2) emissions?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"The largest sources of SO2 emissions are from fossil fuel combustion at power plants andother industrial facilities."
Why this source?
  • This is an EPA webpage that explicitly states the largest sources of SO2.
  • It names fossil fuel combustion at power plants (and other industrial facilities) as the largest source.
Web source
Presence: 4/5
"The largest sources of SO2 emissions are from fossil fuel combustion at power plants and other industrial facilities."
Why this source?
  • World Bank text summarizing SO2 sources repeats the same point about power plants and industrial facilities.
  • It states the largest sources are fossil fuel combustion at power plants and other industrial facilities, supporting the EPA claim.
Web source
Presence: 4/5
"Sources: SO2 emissions come primarily from the burning of sulfur-containing fossil fuels, mainly by power plants and other industrial"
Why this source?
  • This source lists SO2 emissions as coming primarily from burning sulfur-containing fossil fuels, mainly by power plants and other industrial sources.
  • It corroborates that power-plant fossil fuel combustion is a primary source of SO2.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 5.5.1. Major sources > p. 77
Strength: 4/5
“• power plants creating electricity from fossil fuel • r'ater as a cooling agent in industrial facilities All rights reserved. No part of this material may be reproduced in any form without permission in writing.”
Why relevant

Lists 'power plants creating electricity from fossil fuel' as a key item under major sources of pollution, implying power plants are important emitters.

How to extend

A student could compare this assertion with EPA sector-by-sector emission inventories (power generation vs. other sectors) to assess if power plants are the largest SO2 source.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Acidification > p. 8
Strength: 5/5
“motor vehicles inject large amounts of these chemicals into the atmosphere. In the atmosphere, the chemicals combine with water to form sulphuric acid and nitric acid. Tese droplets may be transported at great distances by wind before they precipitate to the ground (Fig. 6.1). Te main gases involved in the production of acid rains are nitrogen oxides—sulphur dioxide (SO2), nitrogen dioxide (NO2) and nitrous oxide (NO). Te major sources of these gases is due to burning of fossil fuel and industrial processes. Acid rain is a phrase that applies to a process that results in deposition of acid on the surface of the Earth.”
Why relevant

States that the main gases involved (including SO2) come mainly from burning fossil fuel and industrial processes, tying SO2 production to fossil-fuel combustion.

How to extend

One could use this rule to focus on fossil-fuel-burning sectors (electricity generation, industry, transport) in EPA data to see which sector emits most SO2.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > S.r5.7. Control Measures: > p. 106
Strength: 5/5
“Reducing or eliminating the sources of poilution by • r Buffering - the practice of adding a neutralizing agent to the acidified water to increase the pH is one of the important control measures. Usually lime in the form of calcium oxide and calcium carbonate is used. • r Reducing the emission of SO<sub>2</sub> from power stations by burning less fossil fuel, using alternate energy sources like tidal, wind, hydropower etc., • . using low sulphur fuel; • r desulphurization • r decreasing emission of NO<sub>x</sub> from power stations and • r Modification of engines r Neutralizing it and using it in the manufacture of other products.”
Why relevant

Recommends 'reducing the emission of SO2 from power stations by burning less fossil fuel' and lists control measures specific to power stations, indicating power stations are a notable target for SO2 reduction.

How to extend

A student could treat power stations as a likely major source and check EPA emissions tables or trends for SO2 by source category to verify relative share.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Measures to Check Efects of Acidic Precipitation > p. 10
Strength: 4/5
“Both in the developed and developing countries various remedial measures have been taken to reduce the adverse afect of acidic precipitation. Some of the remedial steps are: • (i) Curtailing the emission of harmful gases and substances from the thermal and other chemical plants.• (ii) Compelling the industries to use better quality of coal which has low emission level of sulphur and other harmful substances.• (iii) Using alternate technologies for efcient use of fossil fuels.• (iv) Implementation of the environmental pollution laws more efectively.• (v) Environmental Impact Assessment on plants, animals, humanity and ecology before the establishment of any major or minor industry.• (vi) Public awareness about acidic rain and its impact on economy, society and ecology.”
Why relevant

Lists curtailing emissions from 'thermal and other chemical plants' and use of low-sulfur coal as remedies for acid precipitation, linking thermal/power plants to SO2 concerns.

How to extend

Use this to narrow investigation to thermal (coal/oil) power plants in EPA inventories and compare their SO2 contributions to other industrial sources.

INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 9: Geographical Perspective on Selected Issues and Problems > Air Pollution > p. 97
Strength: 3/5
“Air pollution is taken as addition of contaminants, like dust, fumes, gas, fog, odour, smoke or vapour to the air in substantial proportion and duration that may be harmful to flora and fauna and to property. With increasing use of varieties of fuels as the source of energy, there is a marked increase in emission of toxic gases into the atmosphere resulting in the pollution of air. Combustion of fossil fuels, mining and industries are the main sources of air pollution. These processes”
Why relevant

Says combustion of fossil fuels, mining and industries are main sources of air pollution, providing a general pattern that fossil-fuel combustion sectors (including power generation) are key emitters.

How to extend

Combine this general pattern with EPA sector breakdowns (power plants vs. vehicles vs. industry) to judge whether power plants dominate SO2 emissions.

Pattern takeaway: The 'Authority Citation Trap': UPSC adds 'According to [Agency]' to standard static questions to test confidence. The strategy is to strip the agency name and answer based on first principles. If the question asks for the largest source of a major pollutant, it is almost always the sector associated with its primary chemical precursor (Sulfur -> Coal -> Power Plants).
How you should have studied
  1. [THE VERDICT]: Sitter disguised as Current Affairs. Source: General Knowledge / Shankar IAS (Chapter on Pollution) / NCERT Class XII Geography.
  2. [THE CONCEPTUAL TRIGGER]: Environmental Pollution > Criteria Pollutants > Source Apportionment (Who emits what?).
  3. [THE HORIZONTAL EXPANSION]: Memorize the 'Largest Source' for other key pollutants: 1. NOx: Transportation (Mobile sources). 2. CO: Transportation (incomplete combustion). 3. Ammonia (NH3): Agriculture (Livestock waste/Fertilizers). 4. VOCs: Solvents/Industrial use. 5. Mercury: Coal Power Plants & Gold Mining. 6. Methane: Agriculture/Enteric Fermentation.
  4. [THE STRATEGIC METACOGNITION]: When UPSC cites a foreign body (EPA/WHO) for a scientific question, they are usually validating a 'General Truth', not a 'Niche Exception'. If standard books say Power Plants are the main SO2 culprit, the EPA likely agrees. Do not overthink or look for obscure exceptions.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Primary sources of sulfur dioxide (SO2)
💡 The insight

Sulfur dioxide originates chiefly from burning fossil fuels and from volcanic activity, which defines the main natural and anthropogenic pathways for SO2 emissions.

High-yield for environment sections: knowing SO2 origins is essential to explain acidification, health impacts, and sectoral responsibility. Connects pollution-source questions with mitigation policies and international/regional emission inventories. Enables answering questions about prioritising control measures and differentiating natural vs human sources.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 6: Geomorphic Movements > Anthropogenic Solution Weathering > p. 91
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Acidification > p. 8
🔗 Anchor: "According to the U.S. Environmental Protection Agency (EPA), are locomotives usi..."
📌 Adjacent topic to master
S1
👉 Fossil-fuel combustion as a driver of acid rain
💡 The insight

Combustion of fossil fuels releases SO2 and nitrogen oxides that chemically form acidic compounds deposited as acid rain.

Directly relevant to questions on acidification, environmental management and regulatory responses; links energy production, industrial processes and environmental impacts. Helps frame policy and technical remedy answers (e.g., fuel quality, emission controls, EIA requirements).

📚 Reading List :
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Acidification > p. 8
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Measures to Check Efects of Acidic Precipitation > p. 10
🔗 Anchor: "According to the U.S. Environmental Protection Agency (EPA), are locomotives usi..."
📌 Adjacent topic to master
S1
👉 Rail traction switch (steam/diesel → electric) and emissions
💡 The insight

Transitioning locomotives from steam and diesel traction to electric traction is a historical and policy measure aimed at reducing pollution from rail transport.

Useful for transport and environment overlap questions: demonstrates sectoral mitigation (electrification) and links to energy supply choices and industrial policy. Enables discussion of technology choices, their environmental trade-offs, and infrastructure planning in answers.

📚 Reading List :
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 12: Transport, Communications and Trade > Main Features of Indian Railways > p. 12
🔗 Anchor: "According to the U.S. Environmental Protection Agency (EPA), are locomotives usi..."
📌 Adjacent topic to master
S2
👉 Anthropogenic sources of SO2 (coal and petroleum dominance)
💡 The insight

Burning coal and petroleum products are the principal human-caused sources of sulfur dioxide emissions.

High-yield for questions on air pollution sources and mitigation policy; links energy choices to pollution outcomes and helps answer questions on source apportionment and regulatory priorities. Useful for reasoning about sectoral emission controls (power plants, transport, industry).

📚 Reading List :
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Acidification > p. 8
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > a) Sulphur > p. 102
🔗 Anchor: "According to the U.S. Environmental Protection Agency (EPA), are ships using fos..."
📌 Adjacent topic to master
S2
👉 Fossil-fuel combustion as a driver of multiple air pollutants
💡 The insight

Combustion of fossil fuels emits SO2, nitrogen oxides, and CO2, contributing to acid rain and broader air pollution problems.

Important for integrated questions connecting climate change, acidification, and air quality policy; helps frame cross-cutting answers on co-benefits of reducing fossil-fuel use and technologies (e.g., cleaner fuels, emission controls).

📚 Reading List :
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Acidification > p. 8
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > The main sources > p. 256
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > 20.1. Composition of The Earth's Atmosphere > p. 270
🔗 Anchor: "According to the U.S. Environmental Protection Agency (EPA), are ships using fos..."
📌 Adjacent topic to master
S2
👉 Natural versus anthropogenic sulfur sources
💡 The insight

Sulfur compounds come from natural processes (volcanoes, seas, biological decay) as well as human activities like fuel burning and metal smelting.

Useful for distinguishing baseline natural emissions from policy-relevant anthropogenic emissions; aids in answering questions on attribution, monitoring priorities, and the design of emission reduction strategies.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > a) Sulphur > p. 102
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 6: Geomorphic Movements > Anthropogenic Solution Weathering > p. 91
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Sources of Marine Pollution > p. 46
🔗 Anchor: "According to the U.S. Environmental Protection Agency (EPA), are ships using fos..."
📌 Adjacent topic to master
S3
👉 Major anthropogenic sources of SO2
💡 The insight

Burning of coal and petroleum are identified as large human-caused contributors to SO2, alongside metallurgical activities.

High-yield for environment and economy questions: distinguishes dominant industrial emitters (fossil-fuel combustion) from other sources, links to air pollution control policy and energy questions, and helps answer questions on emission inventories and mitigation priorities.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > a) Sulphur > p. 102
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > 20.1. Composition of The Earth's Atmosphere > p. 270
🔗 Anchor: "According to the U.S. Environmental Protection Agency (EPA), is extraction of me..."
🌑 The Hidden Trap

Since they asked SO2 (Stationary Source dominant), the next logical question is Nitrogen Oxides (NOx). Unlike SO2, the largest source of NOx is usually Transportation (Mobile Sources). Be ready for this inversion.

⚡ Elimination Cheat Code

Use the 'Raw vs. Refined' Heuristic. Power plants burn raw Coal (high sulfur). Locomotives and Ships burn Diesel/Fuel Oil (refined products). Even with 'bunker fuel' being dirty, the sheer volume of coal burned 24/7 by power plants dwarfs the fuel consumption of transport sectors. Scale dictates the answer.

🔗 Mains Connection

Mains GS-3 (Environment): Link this to 'Flue Gas Desulphurization (FGD)' technology. The Ministry of Power has repeatedly extended deadlines for thermal plants to install FGD units to cut SO2. This connects the Prelims fact (Source) to the Mains issue (Policy Implementation & Delay).

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SIMILAR QUESTIONS

NDA-II · 2016 · Q78 Relevance score: -2.43

Which one of the following sectors is the largest contributor to carbon dioxide emissions from fuel consumption in India ?

IAS · 2025 · Q38 Relevance score: -2.94

Consider the following statements: 1. Carbon dioxide (CO₂) emissions in India are less than 0.5 t CO₂/capita. 2. In terms of CO₂ emissions from fuel combustion, India ranks second in Asia-Pacific region. 3. Electricity and heat producers are the largest sources of CO₂ emissions in India. Which of the statements given above is/are correct?

IAS · 2011 · Q2 Relevance score: -3.04

Consider the following: 1. Carbon dioxide 2. Oxides of Nitrogen 3. Oxides of Sulphur Which of the above is/ are the emission/ emissions from coal combustio nat thermal power plants ?

IAS · 2019 · Q35 Relevance score: -3.53

Consider the following : 1. Carbon monoxide 2. Methane 3. Ozone 4. Sulphur dioxide Which of the above are released into atmosphere due to the burning of crop/biomass residue?

CAPF · 2025 · Q125 Relevance score: -3.60

Which one among the following is not a greenhouse gas?