Ozone day is celebrated on :

Question

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Correct — A, 16th September. The day's full name is the International Day for the Preservation of the Ozone Layer, and the date was not picked for convenience: the United Nations General Assembly proclaimed it in 1994, by resolution 49/114, specifically to commemorate the signing on 16 September 1987 of the Montreal Protocol on Substances that Deplete the Ozone Layer. The sequence behind that signature is worth holding as one chain. Scientific confirmation that the ozone layer was thinning pushed governments to build a cooperation mechanism, which took shape as the Vienna Convention for the Protection of the Ozone Layer, adopted and signed by 28 countries on 22 March 1985; that convention is a framework — it commits parties to cooperate and monitor, but sets no binding cuts. The binding instrument is the Montreal Protocol, drafted in September 1987 and in force from 1 January 1989, which controls nearly 100 chemicals — chlorofluorocarbons, halons, carbon tetrachloride, methyl chloroform, methyl bromide and the hydrochlorofluorocarbons brought in as transitional substitutes — each group with its own phase-out timetable, and with 'consumption' defined as production plus imports minus exports, less verified destruction. A handful of essential-use exemptions survive where no substitute works, notably metered-dose inhalers for asthma and halon fire-suppression systems in submarines and aircraft. The Protocol has been revised repeatedly: London 1990, Copenhagen 1992, Vienna 1995, Montreal 1997, Beijing 1999, Montreal 2007, Kigali 2016 and Quito 2018. The same date carries a second anniversary that examiners like — on 16 September 2009 the Vienna Convention and the Montreal Protocol became the first treaties in the history of the United Nations to achieve universal ratification. The 2025 observance fell three days after this paper was written, on the theme 'From science to global action', marking forty years since the Vienna Convention; the World Meteorological Organization's assessment is that the ozone layer's recovery is on track and that the ozone treaties additionally help avoid about 0.5 °C of global warming.

Why the other options are wrong — (b) 5 June is World Environment Day, the United Nations' principal environmental outreach day, run by the UN Environment Programme and observed since the 1970s. It is the strongest distractor precisely because it is the one environment date almost every candidate knows, so a hurried reader picks it by reflex. But its subject is the environment at large — plastics, air pollution, ecosystems — and it has no connection to the ozone layer or to the Montreal Protocol.  (c) 21 April is observed in India as National Civil Services Day and has no environmental content at all. What makes it dangerous is that it sits one day away from a date that does: Earth Day is 22 April, first held on 22 April 1970 and now coordinated in more than 193 countries. A candidate who half-remembers 'something environmental in late April' can convert a one-day slip into a lost mark plus the negative marking.  (d) 5 December is World Soil Day, endorsed by the Food and Agriculture Organization and the UN General Assembly, and an official international day only since 2014, established under the leadership of the Kingdom of Thailand — which is why its main honour is the King Bhumibol World Soil Day Award. It concerns soil health, degradation and food security: the ground, not the stratosphere.

Concept: Ozone is O₃, and about ninety per cent of the Earth's ozone sits in the stratosphere, in a diffuse band roughly 15 to 35 km up, where it absorbs the ultraviolet-B radiation that would otherwise reach the surface and cause skin cancers, cataracts and damage to crops and plankton. Its thickness is reported in Dobson Units, and the Antarctic 'ozone hole' is conventionally the area where the column falls below 220 DU. The damage mechanism is catalytic. Chlorofluorocarbons are chemically inert in the lower atmosphere, which is exactly why they were adopted as refrigerants, aerosol propellants and foam-blowing agents; being inert, they survive long enough to drift into the stratosphere, where short-wave ultraviolet light finally breaks them apart and frees chlorine atoms. Each freed atom destroys ozone and is regenerated, so a single atom cycles through the reaction many times over. Bromine, released from halons and methyl bromide, is more destructive still per atom than chlorine. The hole is Antarctic and seasonal because the winter polar vortex isolates the air and lets polar stratospheric clouds form, whose surfaces convert unreactive reservoir chlorine into forms that attack ozone as soon as the spring sun returns. Two distinctions matter for exams. Stratospheric ozone is protective while ground-level ozone is a harmful secondary pollutant formed in photochemical smog. And the Montreal Protocol addresses ozone depletion, whereas the Kyoto Protocol and the Paris Agreement address climate change — related atmospheric problems, entirely different treaties.

State PCS 2025 Q149 — Environment & Ecology PYQ with Answer

State PCS 2025 Q149 — Environment & Ecology PYQ with Answer