UPSC Prelims 2020
Environment & Ecology Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3 only

Steel slag, a by-product of steel manufacturing, has multiple applications in construction, agriculture, and cement production. All three statements correctly identify valid uses of steel slag.

✅ Statement 1 – Correct: Steel slag is widely used in road base construction due to its high strength, durability, excellent drainage properties, and cost-effectiveness.

✅ Statement 2 – Correct: Steel slag can be used as a soil amendment in agriculture to improve drainage, provide essential nutrients like calcium and magnesium, correct soil pH, and enhance soil structure.

✅ Statement 3 – Correct: Steel slag can be used as a partial substitute for limestone and other raw materials in cement production, reducing environmental impact and conserving natural resources.

📝 Short Notes: Steel Slag Utilization

• Definition: Steel slag is a by-product generated during steel manufacturing in furnaces, consisting primarily of calcium, iron, silicon, and magnesium oxides.
• Road Construction: Used as aggregate in asphalt concrete, road base material, and railway ballast due to high abrasion resistance and load-bearing capacity.
• Agricultural Use: Acts as a soil conditioner, neutralizes acidic soils, supplies micronutrients, and improves soil permeability.
• Cement Industry: Can replace 10-15% of clinker in cement production, reducing CO₂ emissions and energy consumption.
• Other Applications: Used in wastewater treatment, coastal protection structures, and as a raw material for mineral wool production.
• Environmental Benefits: Reduces landfill waste, conserves natural resources, and supports circular economy principles in steel industry.

Detailed Explanation:

Answer: Option 3 — Nagarjunsagar-Srisailam

Nagarjunsagar-Srisailam Tiger Reserve, spread across five districts in Andhra Pradesh and Telangana, has the largest Critical Tiger Habitat (CTH) among the given options with a total area of approximately 3,728 sq. km. Critical Tiger Habitats are core areas of tiger reserves notified under the Wildlife Protection Act, 1972, which are kept inviolate for tiger conservation based on scientific evidence.

📝 Short Notes: Major Tiger Reserves and Their Critical Tiger Habitat Areas

• Critical Tiger Habitat (CTH): Also called core areas, these are inviolate zones notified under Section 38V of the Wildlife Protection Act, 1972, where human activities are prohibited or severely restricted.
• Buffer Zones: Areas surrounding CTH where limited human activity is permitted with conservation-oriented management.
• India has 53 tiger reserves (as of 2023) covering about 75,000 sq. km across 18 states.
• Project Tiger was launched in 1973 with 9 tiger reserves; Corbett was the first.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

All three statements about coal combustion and Indian coal characteristics are correct. Coal ash contains heavy metals, coal-fired power plants release sulfur and nitrogen oxides, and Indian coal is characterized by high ash content.

✅ Statement 1 – Correct: Coal ash, a by-product of coal combustion, contains toxic heavy metals including arsenic, lead, and mercury, which can leach into water bodies and contaminate soil, posing environmental and health hazards.

✅ Statement 2 – Correct: Coal-fired power plants release sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) during combustion, which contribute to acid rain, respiratory issues, smog formation, and overall air pollution.

✅ Statement 3 – Correct: Indian coal, especially from eastern and central regions, has high ash content (30-50%), which reduces its calorific value, increases pollution levels, and results in large quantities of fly ash generation in thermal power plants.

📝 Short Notes: Coal Combustion and Environmental Impact

• Coal Ash Composition: Contains heavy metals (arsenic, lead, mercury, chromium, cadmium) that are toxic and carcinogenic; improper disposal can contaminate groundwater and soil.
• Air Pollutants from Coal Plants: Release SO₂ (causes acid rain), NOₓ (forms ground-level ozone and smog), particulate matter (PM2.5, PM10), CO₂ (greenhouse gas), and mercury emissions.
• Indian Coal Characteristics: High ash content (30-50% compared to 10-15% in imported coal), low calorific value (3000-4000 kcal/kg), and high moisture content.
• Fly Ash Utilization: India generates over 200 million tonnes of fly ash annually; used in cement manufacturing, brick making, road construction, and land filling.
• Environmental Regulations: MoEFCC mandates 100% fly ash utilization; thermal power plants must maintain electrostatic precipitators and FGD (Flue Gas Desulfurization) systems.

Detailed Explanation:

Answer: Option 3 — 1 and 3 only

Desert National Park is one of India's largest national parks, spread across Jaisalmer and Barmer districts of Rajasthan, representing the Thar Desert ecosystem. It is a crucial habitat for the critically endangered Great Indian Bustard, though human settlements do exist within the park boundaries.

✅ Statement 1 – Correct: The park is spread across Jaisalmer and Barmer districts of Rajasthan, covering approximately 3,162 km².
❌ Statement 2 – Incorrect: Human habitation exists within the park; several villages and communities engaged in livestock rearing are located inside.
✅ Statement 3 – Correct: It is one of the last remaining natural habitats of the critically endangered Great Indian Bustard (Ardeotis nigriceps).

📝 Short Notes: Desert National Park

• Location: Jaisalmer and Barmer districts, Rajasthan
• Area: Approximately 3,162 km², one of the largest national parks in India
• Ecosystem: Represents the Thar Desert ecosystem with sand dunes (20%), rocky terrain, salt lake bottoms, and sparse vegetation
• Key Wildlife: Great Indian Bustard (critically endangered), Chinkara, Desert Fox, Desert Cat, Wolf
• Human Presence: Unlike strict protected areas, villages and pastoral communities exist within the park
• Conservation Significance: Last stronghold for Great Indian Bustard; captive breeding programs ongoing
• Bird Diversity: Over 140 bird species recorded, including migratory and resident species

Detailed Explanation:

Answer: Option 1 — Birds

All four species mentioned—Ceylon frogmouth, Coppersmith barbet, Gray-chinned minivet, and White-throated redstart—are birds found in India and neighboring regions. The Ceylon frogmouth is a nocturnal bird of the Western Ghats, the Coppersmith barbet is named for its metallic call, the Gray-chinned minivet is known for its colorful plumage, and the White-throated redstart is characterized by its distinctive red tail.

📝 Short Notes: Indian Bird Species

• Ceylon Frogmouth (Batrachostomus moniliger): A nocturnal bird native to the Western Ghats and Sri Lanka; resembles a frog due to its wide mouth and camouflaged plumage; inhabits dense tropical forests.
• Coppersmith Barbet (Psilopogon haemacephalus): A resident bird across the Indian subcontinent; named for its repetitive metallic 'tuk-tuk-tuk' call resembling a coppersmith's hammer; features crimson forehead and throat with green body.
• Gray-chinned Minivet (Pericrocotus solaris): Found in the Himalayas and Southeast Asia; exhibits sexual dimorphism with males displaying orange-red plumage and females showing yellow; inhabits subtropical and temperate forests.
• White-throated Redstart (Phoenicurus schisticeps): A small passerine bird found in the Himalayas, Nepal, Bhutan, and parts of China; males have black plumage with white throat and bright rufous-red tail; prefers high-altitude scrublands and rocky areas.
• Biodiversity Significance: These species represent India's rich avian diversity across different ecological zones—from tropical forests to high-altitude regions—highlighting the importance of habitat conservation.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

Biochar is a carbon-rich, porous material produced through pyrolysis of biomass. It serves multiple functions in agriculture by improving soil structure, supporting beneficial microorganisms, and enhancing water retention. All three statements correctly describe the agricultural uses of biochar.

✅ Statement 1 – Correct: Biochar can be used as a component of growing media in vertical farming systems, where it improves substrate structure and nutrient retention.
✅ Statement 2 – Correct: The porous structure and chemical properties of biochar create favorable conditions for nitrogen-fixing microorganisms, enhancing biological nitrogen fixation in the soil.
✅ Statement 3 – Correct: Due to its high porosity and large surface area, biochar can absorb and retain significant amounts of water, making it available to plants over extended periods.

📝 Short Notes: Biochar in Agriculture

• Definition: Biochar is a stable, carbon-rich solid obtained from the pyrolysis (thermal decomposition in absence of oxygen) of biomass.
• Soil Amendment: Improves soil structure, porosity, and cation exchange capacity (CEC), leading to better nutrient retention.
• Water Retention: Its porous nature can hold 2-5 times its weight in water, reducing irrigation requirements.
• Microbial Habitat: Provides surface area and micro-habitats for beneficial soil microorganisms, including nitrogen-fixing bacteria.
• Carbon Sequestration: Stores carbon in soil for hundreds to thousands of years, contributing to climate change mitigation.
• Nutrient Management: Reduces nutrient leaching, improves fertilizer efficiency, and can adsorb contaminants.
• Applications: Used in conventional farming, vertical farming, container gardening, and soil remediation projects.

Detailed Explanation:

Answer: Option 1 — 1, 2 and 3 only

For ensuring environmental sustainability and reducing carbon footprint in rural road construction, copper slag (a by-product reducing natural resource demand), cold mix asphalt (lower temperature processing with reduced emissions), and geotextiles (synthetic materials minimizing excavation and resource use) are preferred. Hot mix asphalt requires high energy consumption, and Portland cement production is carbon-intensive, making them less environmentally sustainable choices.

✅ Statement 1 – Correct: Copper slag, a copper refining by-product, can replace sand in concrete, reducing sand mining and environmental impact.
✅ Statement 2 – Correct: Cold mix asphalt technology operates at lower temperatures, consuming less energy and emitting fewer greenhouse gases compared to hot mix.
✅ Statement 3 – Correct: Geotextiles provide soil stabilization and drainage while reducing the need for excessive excavation and natural resource consumption.
❌ Statement 4 – Incorrect: Hot mix asphalt technology requires high temperatures and thus higher energy consumption, making it less environmentally sustainable.
❌ Statement 5 – Incorrect: Portland cement production is highly energy-intensive and emits significant CO₂, contributing substantially to carbon footprint.

📝 Short Notes: Sustainable Road Construction Materials

• Green Road Construction: Focus on using industrial by-products, recycled materials, and low-energy technologies
• Rural Road Context: PMGSY (Pradhan Mantri Gram Sadak Yojana) encourages use of sustainable materials and local resources
• Geotextiles Applications: Separation, filtration, drainage, reinforcement, and erosion control in road construction
• Fly Ash & Slag: Other industrial by-products increasingly used as sustainable alternatives in road construction

Detailed Explanation:

Answer: Option 1 — 1 and 2 only

Musk deer are found in high-altitude Himalayan regions, typically above 2,500 meters. Askot Wildlife Sanctuary and Gangotri National Park, both located in Uttarakhand's Himalayan ranges, provide the ideal alpine and subalpine habitat for musk deer. Kishanpur Wildlife Sanctuary consists of terai grasslands unsuitable for musk deer, while Manas National Park in Assam is a lowland tropical forest ecosystem that does not support musk deer populations.

✅ Statement 1 – Correct: Askot Wildlife Sanctuary in Uttarakhand is specifically known for musk deer conservation in high-altitude Himalayan habitat.
✅ Statement 2 – Correct: Gangotri National Park in Uttarakhand is a high-altitude region where musk deer are naturally found.
❌ Statement 3 – Incorrect: Kishanpur Wildlife Sanctuary in Uttar Pradesh has terai grasslands, not the high-altitude habitat required by musk deer.
❌ Statement 4 – Incorrect: Manas National Park in Assam is a lowland tropical forest unsuitable for musk deer which require alpine habitats.

📝 Short Notes: Musk Deer

• Scientific Name: Moschus species (Himalayan Musk Deer - Moschus leucogaster)
• Habitat: High-altitude Himalayan forests (2,500-4,500 m), alpine meadows, and scrub zones
• Distribution in India: Uttarakhand, Himachal Pradesh, Jammu & Kashmir, Sikkim, and Arunachal Pradesh
• Conservation Status: Endangered (IUCN); Schedule I (Wildlife Protection Act, 1972)
• Key Feature: Males possess musk gland (pod) that produces valuable musk, leading to illegal poaching
• Protected Areas: Askot Wildlife Sanctuary, Gangotri National Park, Kedarnath Wildlife Sanctuary, Great Himalayan National Park, Nanda Devi National Park
• Threats: Habitat loss, poaching for musk, climate change affecting alpine habitats

Detailed Explanation:

Answer: Option 1 — 1 and 2 only

Indian elephants live in matriarchal societies where the oldest and most experienced female leads the herd, while males typically live solitary lives or form bachelor groups. The gestation period of elephants is the longest among land mammals, ranging from 18 to 22 months.

✅ Statement 1 – Correct: Elephant herds are matriarchal, led by the oldest and most experienced female (matriarch), while adult males usually live alone or in bachelor groups.

✅ Statement 2 – Correct: Elephants have the longest gestation period among mammals, ranging from 18 to 22 months, with an average of about 22 months.

❌ Statement 3 – Incorrect: Female elephants can continue to reproduce well beyond 40 years of age, often calving into their 50s and sometimes even early 60s, though fertility may decline with age.

❌ Statement 4 – Incorrect: Karnataka has the highest elephant population in India (around 6,000), followed by Assam and Kerala. Kerala ranks third, not first.

📝 Short Notes: Indian Elephants

• Scientific Name: Elephas maximus indicus (subspecies of Asian elephant)
• Protection Status: Schedule I of Wildlife Protection Act, 1972; Appendix I of CITES; IUCN Red List - Endangered
• Social Structure: Matriarchal herds of 6-12 individuals led by the oldest female; adult males are solitary or form temporary bachelor groups
• Reproduction: Gestation period 18-22 months (longest among mammals); females reach sexual maturity at 10-12 years; can reproduce until 50-60 years of age; typically give birth to one calf every 4-5 years
• Distribution in India: Karnataka (highest population ~6,000), Assam (~5,700), Kerala (~3,000), Tamil Nadu, and northeastern states
• Project Elephant: Launched in 1992 to protect elephants, their habitats, and migration corridors; 33 elephant reserves established across 16 states
• Major Threats: Habitat loss and fragmentation, human-elephant conflict, poaching for ivory (though Indian elephants have smaller tusks than African elephants), railway and road accidents

Detailed Explanation:

Answer: Option 4 — Neither 1 nor 2

Solar water pumps are versatile and can power both surface and submersible pumps, as well as both centrifugal and piston pumps. The type of pump (surface/submersible or centrifugal/piston) does not limit the application of solar power, making both statements incorrect.

❌ Statement 1 – Incorrect: Solar power can be used for running both surface pumps and submersible pumps, not just surface pumps.
❌ Statement 2 – Incorrect: Solar power can be used for running both centrifugal pumps and piston pumps, not just centrifugal pumps.

📝 Short Notes: Solar Water Pumping Systems

• Components: A solar water pumping system consists of three main components: photovoltaic (PV) array/solar panels, an electric motor (DC/AC/BLDC), and a pump.
• Types by Motor: Systems are classified as Direct Current (DC), Alternating Current (AC), or Brushless DC (BLDC) based on the motor type.
• Types by Pump Installation: Can use surface pumps (installed above ground) or submersible pumps (installed underwater in wells/borewells).
• Types by Pump Mechanism: Both centrifugal pumps (using rotational energy) and positive displacement pumps like piston pumps can be solar-powered.
• Applications: Ideal for irrigation, drinking water supply, livestock watering, and remote areas without grid electricity.
• Benefits: Clean, energy-efficient, sustainable, low operating costs, minimal maintenance, and environmentally friendly alternative to diesel/electric pumps.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

Zero tillage is a conservation agriculture practice where seeds are sown directly into untilled soil, leaving crop residues on the field. This method offers multiple environmental and economic benefits including reduced labor costs, improved soil health, and enhanced carbon storage.

✅ Statement 1 – Correct: Zero tillage allows wheat sowing directly into fields with previous crop residue (like rice stubble) intact, eliminating the need for burning, which reduces air pollution and preserves soil nutrients.
✅ Statement 2 – Correct: Direct seeding of paddy (DSR - Direct Seeded Rice) in wet soil is possible under zero tillage, bypassing the traditional nursery-transplanting method, saving water, labor, and time.
✅ Statement 3 – Correct: By leaving crop residues undisturbed and minimizing soil disturbance, zero tillage enhances organic matter retention and carbon sequestration in soil, mitigating climate change.

📝 Short Notes: Zero Tillage/Conservation Agriculture

Detailed Explanation:

Answer: Option 1 — 1, 2, 5 and 6 only

India's National Policy on Biofuels (2018) permits the use of surplus food grains, damaged grains, starch-rich crops like cassava, and sugar-rich crops like sugar beet for ethanol production. Oil-seed crops and protein-rich pulses like groundnut seeds and horse gram are not included as feedstock for biofuels to avoid competition with edible oil and food supply.

✅ Statement 1 – Correct: Cassava is a starchy root crop explicitly allowed as feedstock for ethanol production under the policy.
✅ Statement 2 – Correct: Damaged wheat grains (surplus or non-edible) can be diverted for biofuel production to prevent wastage.
❌ Statement 3 – Incorrect: Groundnut seeds are oil-seeds and not permitted for biofuel production to avoid competition with edible oil markets.
❌ Statement 4 – Incorrect: Horse gram is a pulse (protein-rich crop) and is not included in the biofuel feedstock list.
✅ Statement 5 – Correct: Rotten potatoes (damaged/surplus tubers) can be used for biofuel production as waste utilization.
✅ Statement 6 – Correct: Sugar beet is a sugar-rich crop approved for ethanol production under the policy.

📝 Short Notes: National Policy on Biofuels 2018

• First Generation (1G) Biofuels: Produced from sugars, starch, vegetable oils – includes bioethanol and biodiesel.
• Second Generation (2G) Biofuels: Produced from non-food biomass like agricultural residues, forest waste, municipal solid waste.
• Allowed Feedstock for Ethanol: Sugarcane, sugar beet, cassava, damaged food grains, surplus food grains, sweet sorghum.
• Allowed Feedstock for Biodiesel: Non-edible oilseeds (Jatropha, Karanja, Mahua, etc.), used cooking oil, animal fat.
• Not Allowed: Edible oil-seeds (groundnut, soybean, sunflower), pulses and protein-rich crops to avoid food security concerns.
• Ethanol Blending Target: 20% by 2025 (E20) for petrol blending.
• Indicative Biodiesel Blending Target: 5% by 2030.

Detailed Explanation:

Answer: Option 1 — A licence is required to cultivate that plant.

Schedule VI of the Wildlife Protection Act, 1972, specifically lists plant species for which cultivation and planting are prohibited without obtaining a proper licence from the authorities. This provision ensures regulated cultivation of certain sensitive plant species to prevent their exploitation and maintain ecological balance. The other options are incorrect as Schedule VI does not prohibit cultivation entirely, nor does it relate to GMOs or invasive species classification.

📝 Short Notes: Wildlife Protection Act, 1972 - Schedules

• 2022 Amendment: Reduced schedules from six to four, merging and reclassifying species for better alignment with CITES requirements.
• CITES Integration: Schedule IV now specifically covers species listed under CITES, facilitating international trade regulation and conservation commitments.
• Purpose of Schedule VI: To control cultivation of rare and threatened plant species, prevent commercial exploitation, and ensure sustainable use through licensing mechanism.

Detailed Explanation:

Answer: Option 3 — 1, 3 and 4 only

Fertigation is the technique of applying fertilizers through irrigation systems, allowing precise nutrient delivery to the root zone. This method enables control over irrigation water pH, increases nutrient availability to plants, and reduces nutrient leaching, but cannot be used for water-insoluble fertilizers like rock phosphate.

✅ Statement 1 – Correct: Fertigation allows control of irrigation water alkalinity/pH by adjusting it to optimal levels for nutrient absorption.
❌ Statement 2 – Incorrect: Rock phosphate is not water-soluble and cannot be efficiently applied through fertigation systems, which require water-soluble fertilizers.
✅ Statement 3 – Correct: Fertigation delivers nutrients directly to the root zone, significantly increasing nutrient availability and uptake efficiency.
✅ Statement 4 – Correct: Precise nutrient application through fertigation reduces excess fertilizer use and minimizes nutrient leaching into groundwater.

📝 Short Notes: Fertigation

• Definition: Application of fertilizers through irrigation systems (drip, sprinkler) directly to the crop root zone.
• Water-soluble fertilizers used: Urea, potassium nitrate, calcium nitrate, mono-ammonium phosphate (MAP), di-ammonium phosphate (DAP).
• Key advantages: Uniform nutrient distribution, higher nutrient use efficiency (30-50% savings), labor reduction, timely nutrient supply.
• pH management: Allows adjustment of irrigation water pH through acid injection (phosphoric acid, sulfuric acid) to optimize nutrient availability.
• Reduced leaching: Controlled application prevents over-fertilization and groundwater contamination.
• Limitations: Requires soluble fertilizers, initial setup cost, technical knowledge, and regular maintenance of irrigation system.

Detailed Explanation:

Answer: Option 1 — Kanha National Park

Kanha National Park in Madhya Pradesh is renowned for the conservation of the hard ground barasingha (Southern swamp deer), a unique subspecies of the Indian swamp deer that thrives on hard ground in open sal forests and feeds exclusively on grasses (graminivorous). Conservation efforts by the park have successfully revived this subspecies from near extinction, making it a flagship conservation success story.

📝 Short Notes: Barasingha and Its Conservation

• Barasingha (Rucervus duvaucelii): Also known as the swamp deer, it is a herbivorous species native to the Indian subcontinent, classified as Vulnerable by IUCN.
• Three Subspecies: Northern swamp deer (found in Uttar Pradesh terai), Western swamp deer (found in Nepal), and Southern/hard ground swamp deer (found in central India).
• Hard Ground Barasingha: This subspecies is adapted to hard ground in dry deciduous sal forests, unlike other swamp deer that prefer marshy wetlands.
• Kanha National Park: Located in Madhya Pradesh, it is the primary habitat for hard ground barasingha and has achieved remarkable conservation success since the 1970s.
• Diet: Exclusively graminivorous (grass-eating), feeding on various species of grasses found in forest clearings.
• Other Populations: Northern swamp deer are found in Dudhwa National Park; Manas has the Western subspecies but focuses on other wildlife.

Detailed Explanation:

Answer: Option 3 — 1, 3 and 4 only

This question tests knowledge of Protected Areas located in the Cauvery river basin. Among the given options, Nagarhole National Park, Sathyamangalam Tiger Reserve, and Wayanad Wildlife Sanctuary are located in the Cauvery basin, while Papikonda National Park is located in the Godavari basin.

✅ Statement 1 – Correct: Nagarhole National Park is located in Kodagu and Mysore districts of Karnataka, part of the Nilgiri Biosphere Reserve, and lies within the Cauvery basin.
❌ Statement 2 – Incorrect: Papikonda National Park is located in Andhra Pradesh along the Godavari river basin, not the Cauvery basin.
✅ Statement 3 – Correct: Sathyamangalam Tiger Reserve lies on the banks of River Bhavani, a tributary of Cauvery, in the foothills of the Eastern Ghats in Tamil Nadu.
✅ Statement 4 – Correct: Wayanad Wildlife Sanctuary in Kerala has the Kabini river (a tributary of Cauvery) flowing through it, making it part of the Cauvery basin.

📝 Short Notes: Protected Areas in Cauvery Basin

• Cauvery River: Originates in Talakaveri, Western Ghats of Karnataka; flows through Karnataka, Tamil Nadu, and Puducherry before draining into the Bay of Bengal.
• Nagarhole National Park: Also known as Rajiv Gandhi National Park; part of the Nilgiri Biosphere Reserve; rich in tiger, elephant, and leopard populations.
• Sathyamangalam Tiger Reserve: Located in Erode district, Tamil Nadu; connects the Western and Eastern Ghats; crucial elephant corridor.
• Wayanad Wildlife Sanctuary: Part of the Nilgiri Biosphere Reserve; contiguous with Nagarhole and Bandipur; known for its elephant population.
• Major Tributaries of Cauvery: Hemavati, Shimsha, Arkavathi, Kabini, Bhavani, Amaravati, and Noyyal.
• Papikonda National Park: Located in East and West Godavari districts of Andhra Pradesh; part of Godavari basin; known for its pristine forests and tribal population.

Detailed Explanation:

Answer: Option 1 — Long-term damage done by a tonne of CO2 emissions in a given year.

The Social Cost of Carbon (SCC) is an economic metric that estimates the long-term economic damage caused by emitting one additional tonne of carbon dioxide in a given year. It encompasses various climate-related damages such as impacts on human health, agricultural productivity, property damage from extreme weather events, and ecosystem services. This measure is used by policymakers to assess the economic benefits of reducing CO₂ emissions and to inform cost-benefit analyses of climate policies.

📝 Short Notes: Social Cost of Carbon (SCC)

• Definition: The Social Cost of Carbon represents the monetary value of the total damage caused by emitting one additional tonne of CO₂ in a particular year, measured over the lifetime of that emission.
• Components: Includes damages from sea-level rise, agricultural losses, human health impacts, property damage from increased extreme weather events, and ecosystem disruption.
• Time Horizon: Typically calculated over 100-300 years, as CO₂ remains in the atmosphere for centuries.
• Discount Rate: Uses economic discount rates to convert future damages into present-day monetary values, with rates typically ranging from 2.5% to 5%.
• Policy Application: Used by governments (especially in the US and EU) for regulatory impact assessments, carbon pricing mechanisms, and evaluating climate mitigation projects.
• Variability: SCC estimates vary widely (from $10 to over $400 per tonne of CO₂) depending on assumptions about climate sensitivity, economic models, and discount rates used.

Detailed Explanation:

Answer: Option 1 — 1, 2 and 3 only

Benzene is a colorless, volatile organic compound and a known carcinogen present in the environment through various natural and anthropogenic sources. The main sources of benzene exposure include automobile exhaust (as benzene is present in petrol), tobacco smoke (both active and passive), and wood burning (due to incomplete combustion). Varnished wooden furniture and polyurethane products are not significant sources of benzene pollution.

✅ Statement 1 – Correct: Automobile exhaust, especially from petrol-driven vehicles, is a major source of benzene as it is a component of petroleum products.
✅ Statement 2 – Correct: Tobacco smoke contains benzene and is a significant source of exposure for both smokers and passive smokers.
✅ Statement 3 – Correct: Wood burning releases benzene through incomplete combustion, along with other pollutants like polycyclic aromatic hydrocarbons (PAHs).
❌ Statement 4 – Incorrect: Varnished wooden furniture may emit benzene during application but once cured, it is not a significant source of benzene pollution.
❌ Statement 5 – Incorrect: Polyurethane products are primarily associated with other volatile organic compounds (VOCs), not benzene.

📝 Short Notes: Benzene Pollution

• Nature: Benzene (C₆H₆) is a colorless, highly flammable liquid with a sweet odor, classified as a Group 1 carcinogen by IARC.
• Major Sources: Automobile emissions (petrol combustion), tobacco smoke, industrial processes, petroleum refineries, and incomplete combustion of organic materials (wood, coal).
• Health Effects: Prolonged exposure causes blood disorders, anemia, leukemia, immune system suppression, and reproductive health issues.
• Indoor Sources: Tobacco smoke, attached garages (vehicle emissions), and certain paints/solvents during application.
• Occupational Exposure: Workers in petroleum refineries, chemical plants, rubber manufacturing, and printing industries face higher risks.
• Regulatory Standards: WHO air quality guideline for benzene is minimal (no safe level); ambient air standards vary by country to limit exposure.

Detailed Explanation:

Answer: Option 1 — 1, 2 and 3 only

Eco-friendly agricultural practices minimize environmental harm while maintaining productivity. Crop diversification, legume intensification, and precision irrigation using tensiometers all qualify as sustainable practices in the Indian context, whereas vertical farming's high energy demands make it unsuitable.

✅ Statement 1 – Correct: Crop diversification enhances soil health, increases biodiversity, breaks pest cycles, and reduces chemical pesticide dependence.
✅ Statement 2 – Correct: Legume intensification naturally enriches soil through nitrogen fixation via Rhizobium bacteria, reducing synthetic fertilizer requirements.
✅ Statement 3 – Correct: Tensiometers measure soil moisture tension, enabling precision irrigation that conserves water and prevents nutrient leaching from over-watering.
❌ Statement 4 – Incorrect: Vertical farming in India is not eco-friendly due to its heavy reliance on artificial lighting and climate control systems powered predominantly by fossil fuel-based electricity, creating a large carbon footprint.

📝 Short Notes: Eco-Friendly Agricultural Practices

• Crop Diversification: Growing multiple crop species in rotation or together; improves soil fertility, pest control, and resilience to climate variability.
• Legume Intensification: Increased cultivation of pulses/legumes (e.g., lentils, chickpeas) that fix atmospheric nitrogen naturally, reducing chemical fertilizer use.
• Precision Irrigation: Use of tools like tensiometers, drip irrigation, and soil moisture sensors to optimize water use and prevent wastage.
• Organic Farming: Avoids synthetic chemicals; uses compost, green manure, and biopesticides.
• Agroforestry: Integrating trees with crops/livestock; enhances carbon sequestration and biodiversity.
• Conservation Tillage: Minimal soil disturbance practices like zero-tillage that preserve soil structure and organic matter.
• Integrated Pest Management (IPM): Combines biological, cultural, and mechanical pest control methods to minimize pesticide use.
• Green Manuring: Growing and plowing back green crops (like Sesbania, Dhaincha) to enrich soil organic content.