================================== DOCUMENT 3: SESSION 6 (S6) ================================== POLLUTION ABATEMENT (21CHO105T) Unit 1 - Session 6 I. MULTIPLE CHOICE QUESTIONS (MCQs) 1. Nitric acid in acid rain is formed from β Answer: B) Nitrogen oxides β Explanation: Nitrogen oxides ( , such as ) react with atmospheric moisture ππ π₯ ππ 2 and oxygen to form nitric acid ( ). π»ππ 3 2. Acid rain causes damage to monuments mainly due to β Answer: B) Chemical reaction with stone materials β Explanation: Sulfuric acid in acid rain chemically reacts with calcium carbonate ( ) in marble and limestone to form soluble calcium sulfate ( ), a πΆππΆπ 3 πΆπππ 4 process called "stone cancer." 3. Freshwater organisms are affected by acid rain because of β Answer: C) Changes in water pH β Explanation: Acid rain lowers the pH of lakes and rivers below critical survival limits (often ), leaching toxic aluminum ions ( ) into the water and ππ» < 5 π΄π 3+ disrupting aquatic life. 4. Pollution prevention is preferred over pollution control because it β Answer: C) Reduces environmental damage β Explanation: Pollution prevention eliminates pollutants directly at the source, preventing environmental damage and saving long-term waste treatment and disposal costs. 5. Environmental regulations encourage industries to adopt β Answer: B) Cleaner and efficient technologies β Explanation: Regulatory compliance mandates lower emissions thresholds, motivating industries to transition toward resource-efficient, low-emission technologies. II. SHORT ANSWER QUESTIONS Q1. How is acid rain formed? β Answer: β Emissions: Industrial power plants and vehicles emit gaseous precursorsβsulfur dioxide ( ) and nitrogen oxides ( ). ππ 2 ππ π₯ β Oxidation & Hydration: These gases react with atmospheric oxygen, water vapor, and oxidants: β (Sulfuric acid) ππ 2 + [π] + π» 2 π β π» 2 ππ 4 β (Nitric acid) 2ππ 2 + [π] + π» 2 π β 2π»ππ 3 β Precipitation: These acids dissolve into cloud droplets and fall to Earth as wet deposition (rain, snow, fog) with a ππ» < 5. 6 Q2. What is the main aim of environmental policies? β Answer: β To protect natural ecosystems, biodiversity, and human health from environmental degradation. β To enforce industrial compliance with pollutant discharge limits. β To promote sustainable development through pollution prevention, resource conservation, and adoption of cleaner production technologies. III. LONG ANSWER QUESTION 1. Acid rain is a form of precipitation that contains acidic components such as sulfuric acid and nitric acid. [Discuss the causes, chemical mechanisms, environmental impacts, and control strategies for acid rain.] β Answer: 1. Atmospheric Chemical Reactions Acid rain forms when primary pollutants ( and ) undergo atmospheric ππ 2 ππ π₯ transformation: β Sulfuric Acid Formation: β ππ 2 + ππ» β’ β π»ππ 3 β’ β β π»ππ 3 β’ + π 2 β π»π 2 β’ + ππ 3 β β ππ 3 + π» 2 π β π» 2 ππ 4 β Nitric Acid Formation: β ππ 2 + ππ» β’ β π»ππ 3 2. Environmental and Material Impacts β Aquatic Ecosystems: Lowering water bodies' pH below 5.0 causes acidification, triggering fish egg mortality and leaching toxic aluminum ions ( ) into stream π΄π 3+ systems. β Terrestrial Ecosystems & Forestry: Foliar leaching strips essential plant nutrients ( ) from leaves and soils, stunting forest growth. πΆπ 2+ , ππ 2+ β Built Environment & Cultural Heritage: Acid rain degrades historical structures made of limestone and marble ( ): πΆππΆπ 3 β πΆππΆπ 3 + π» 2 ππ 4 β πΆπππ 4 + πΆπ 2 + π» 2 π 3. Abatement and Control Strategies β Flue Gas Desulfurization (FGD): Installing industrial wet/dry limestone scrubbers to strip up to 95% of from industrial flue gases. ππ 2 β Selective Catalytic Reduction (SCR): Employing ammonia-based catalytic converters to reduce exhaust to inert nitrogen gas ( ). ππ π₯ π 2 β Fuel Clean-up: Utilizing ultra-low-sulfur diesel (ULSD) and hydrodesulfurized coal feedstocks.