Discuss in detail the photochemical smog emphasizing its formation, effects and mitigation. Explain the 1999 Gothenburg Protocol…

Discuss in detail the photochemical smog emphasizing its formation, effects and mitigation. Explain the 1999 Gothenburg Protocol. (Answer in 150 words) 10 marks

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इसके निर्माण, प्रभाव और शमन को महत्व देते हुए फोटोकैमिकल स्मॉग की विस्तारपूर्वक चर्चा कीजिए। 1999 के गोथेनबर्ग प्रोटोकॉल को समझाइए। (150 शब्दों में उत्तर दीजिए)

The question as printed in the 2022 General Studies paper

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Model answer

Drafted with AI by UPSC Answer Check against this question's marking rubric, to the 150-word length. UPSC does not publish answers for Mains — this is one way to score well, not an official key. How we build rubrics and answers.

Photochemical smog is a hazardous haze formed when primary pollutants—Nitrogen Oxides (NOₓ) and Volatile Organic Compounds (VOCs)—react in the presence of solar radiation to generate secondary pollutants, primarily ground-level ozone (O₃), peroxyacetyl nitrate (PAN), and aldehydes. Temperature inversion further traps these pollutants near the surface.

Effects: It triggers respiratory distress, eye irritation, and reduced lung function. It also causes leaf necrosis, retards crop yields, and impairs atmospheric visibility.

Mitigation: Measures include adopting BS-VI vehicular emission norms, installing catalytic converters, vehicle rationing like odd-even schemes, industrial emission limits, and urban greening.

Gothenburg Protocol (1999): Formulated under the UNECE Convention on Long-Range Transboundary Air Pollution, this treaty aims to abate acidification, eutrophication, and ground-level ozone. It employs a multi-pollutant approach, setting national emission ceilings based on "critical loads" for four pollutants: SO₂, NOₓ, VOCs, and NH₃ (later including PM₂.5). India is not a party to this regional protocol.

How this answer will be evaluated

Framework: Environment: threat, causes, impact, mitigation

What earns full marks: Clear chemical mechanism, distinct effects, specific Protocol details (1999, UNECE).

Evaluation rubric

Each sub-part is marked on its own, against the marks and word limit printed on the paper.

The answer Explain photochemical smog (formation, effects, mitigation) and the 1999 Gothenburg Protocol. 10 marks · 150 words

discuss— intro → 3-4 dimensions → example → balanced close
Must cover
- Formation: NOx + VOCs + sunlight -> O3/PAN
- Effects: respiratory issues, crop damage, visibility
- Mitigation: catalytic converters, VOC reduction
- Gothenburg Protocol: 1999 UNECE, acidification/eutrophication limits
Loses marks
- Confusing photochemical smog with industrial smog
- Vague mitigation (e.g., 'plant trees' without context)
- Ignoring the specific year 1999 for the Protocol
Earns more
- Mentions specific precursors (NOx, VOCs)
- Links Protocol to UNECE Convention on LTPC
- Distinguishes photochemical from industrial smog
- Mentions specific pollutants (SO2, NOx, NH3)
Extra mark
- Mentions the 2012 amendment (2020 national targets, PM2.5 added)
- Mentions specific year of entry into force (2005)

What "Discuss" is asking you to do

Lay the issue out from more than one side — how it arose, what is claimed for it, what is held against it, and where it now stands. UPSC attaches discuss to broad topics with several live dimensions, so coverage of the dimensions earns more than the strength of your opinion.

Structure that answers it

Set the issue up → the case as it is made → the case against → the dimension both sides leave out → where the balance now lies

Where marks are lost

Listing facts with no thread between them, or arguing one side throughout and calling it a discussion.

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