Air Pollution & Emissions

✅ A. silver iodide and potassium iodide: True Both are used in cloud seeding because their crystalline structures help form ice nuclei, inducing rainfall. ❌ B. silver nitrate and potassium iodide: False Silver nitrate is not used for artificial rainmaking. ❌ C. silver iodide and potassium nitrate: False Potassium nitrate is not used in cloud seeding. ❌ D. silver nitrate and potassium chloride: False Neither chemical is used in artificial rainmaking. Therefore, option A is correct.

A circular economy focuses on minimizing waste, reusing resources, and improving efficiency, all of which help lower greenhouse gas emissions and conserve raw materials. ✅ Statement I: Correct By reducing waste and energy use, the circular economy helps cut greenhouse gas emissions. ✅ Statement II: Correct It reduces the need for raw materials through reuse, recycling, and product life extension. ✅ Statement III: Correct It also lowers production waste using efficient and sustainable design and processes.

India’s CO₂ emissions come mainly from fuel combustion, especially electricity generation, and per capita emissions are higher than 0.5 tonnes. ❌ Statement I is incorrect:
* India’s per capita CO₂ emissions are around 1.9-2.0 tonnes, higher than 0.5 t CO₂/capita. ✅ Statement II is correct:
* India ranks second in the Asia-Pacific for total CO₂ emissions from fuel combustion, after China. ✅ Statement III is correct:
* Electricity and heat production (mainly coal-based) is the largest source of India’s CO₂ emissions. So, the correct answer is: C

Cement manufacturing contributes significantly to global carbon emissions, mainly due to the chemical process involved in producing clinker. ✅ Statement I: Cement industry emissions are estimated to be around 5-8% of global CO₂ emissions, making it a major source of greenhouse gases. ✅Statement II: Silica-bearing clay is indeed mixed with limestone during cement making to provide essential minerals like silicon, aluminum, and iron needed for the final product. ✅Statement III: During clinker production, limestone (calcium carbonate) is heated and converted into lime (calcium oxide), releasing CO₂ in the process. This calcination is the main source of carbon emissions in cement manufacturing. Both Statements II and III are correct, but only Statement III directly explains the source of carbon emissions mentioned in Statement I.

Direct Air Capture (DAC) is a technology that removes CO₂ directly from the air for storage or use in various industries. ✅ Statement I is correct:
* DAC captures CO₂ for carbon sequestration, reducing greenhouse gases. ✅ Statement II is correct:
* Captured CO₂ can be used to make plastics and in food processing. ✅ Statement III is correct:
* DAC provides carbon to make synthetic low-carbon aviation fuels by combining with hydrogen. So, the correct answer is: C

Power plants burning fossil fuels (coal, oil, and, to a lesser extent, natural gas) are the largest source of sulfur dioxide emissions globally. Coal, in particular, contains high levels of sulfur, and when burned, it releases large amounts of SO₂.    * Locomotives, especially older ones, use diesel fuel which contains sulfur. While locomotives do contribute to sulfur dioxide (SO₂) emissions, their contribution is relatively minor compared to larger industrial sources.   * Ships, particularly large cargo vessels and tankers, often use bunker fuel, a heavy, sulfur-rich fuel oil. This contributes significantly to SO₂ emissions, particularly in maritime regions.  However, they are still overshadowed by emissions from power plants  * The process of extraction of metals from ore involves heating ores that contain sulfur compounds, releasing SO₂ into the atmosphere. However, its contribution is less than that of power plants.

Pyroclastic debris: This is a general term for fragmental material ejected from a volcano during an eruption. It includes ash, pumice, cinders, and volcanic bombs. Ash and dust: These are fine-grained particles of volcanic rock and glass that can be carried long distances by wind. Nitrogen compounds: Nitrogen is a common gas released by volcanoes, and it can react with other elements in the atmosphere to form compounds such as ammonia and nitrogen oxides. Sulphur compounds: Sulphur dioxide (SO2) is one of the main gases released by volcanoes. It can irritate the respiratory system and contribute to acid rain. Other sulphur compounds, such as hydrogen sulphide (H2S), can also be released in smaller amounts. All of the above (1, 2, 3, and 4) are products of volcanic eruptions.

Fuel Cell Electric Vehicles (FCEVs) powered by hydrogen generate electricity by combining hydrogen (H₂) with oxygen (O₂) in a fuel cell. This process produces electricity, heat, and the only exhaust emission is water vapour (H₂O), making hydrogen fuel cells zero-emission.

Out of the above substances, hydrofluorocarbons (HFCs) are used in the making of:  1. Aerosols HFCs were historically used as propellants in aerosol cans, but their use is being phased out due to environmental concerns. 2. Foam agents Some types of fire-fighting foam agents use HFCs. 3. Fire retardant HFCs can be a component in some fire retardant formulations. 4. Lubricants typically do not contain HFCs. They use different chemical formulations to achieve lubricating properties.

* Statement 1 is correct: Gold mining is poisoning Amazon forests with mercury. To separate the gold, miners mix liquid mercury into the sediment, which forms a coating around the gold. * Statement 2 is correct: Fly ash generated by TPPs is one of the ways mercury is released into the environment. Fly ash is usually disposed of in ash ponds in the form of ash slurry, forming an aquatic ecosystem of its own. Coal-based TPPs are the major source of mercury – the ninth most toxic element found on earth — emissions into the environment. Mercury contributed over 80 percent of emissions released by the TPPs, according to 2016 estimates by the Delhi-based think-tank Centre for Science and Environment. * Statement 3 is incorrect: While mercury is unquestionably toxic, toxicology works on the principle of dose: “The dose makes the poison.” Hence, scientific bodies define reference doses (RfD) or tolerable intake levels, not zero exposure. WHO's Provisional Tolerable Weekly Intake (PTWI) for methylmercury (from fish) → 1.6 µg/kg body weight/week and 1 µg/litre for total mercury in drinking water. If no safe level truly existed: Mercury would be completely banned, not regulated. NOTE: UPSC usually considers extreme statement to be wrong.