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Subject: Environment

  • Doomsday Glacier Destabilisation and the Future of Antarctic Ice Sheets

    Why in the News?

    A recent scientific study has revealed increasing fracturing in the Thwaites Glacier, also known as the Doomsday Glacier, indicating how large parts of the Antarctic ice sheets could collapse in the future. The findings were published in the Journal of Geophysical Research: Earth Surface.

    Thwaites Glacier (Doomsday Glacier)

    The Thwaites Glacier is a massive glacier in West Antarctica that drains ice from the West Antarctic Ice Sheet into the Amundsen Sea. It is one of the fastest changing glacier systems on Earth.

    Why it is called the Doomsday Glacier

    • Complete collapse could raise global sea levels by about 65 cm
    • Acts as a gateway glacier whose destabilisation can trigger wider ice sheet collapse
    • Focus area: Thwaites Eastern Ice Shelf (TEIS), a floating extension of the glacier

    Pinning point and shear zone

    • TEIS is attached to an undersea ridge called a pinning point
    • Pinning points slow ice flow but also cause compression and fracturing
    • Upstream of the pinning point lies a shear zone where ice deforms intensely

    Fracture patterns observed

    • Ice fracturing occurred in two stages
      • Long fractures parallel to ice flow
      • Smaller fractures perpendicular to ice flow
    • Annual fracture length increased sharply
      • From about 165 km in 2002
      • To about 335 km in 2022

    Consequences of fracturing

    • Breakdown of the shear zone accelerates ice flow
    • Faster ice flow increases ice discharge into the ocean
    • Raises risk of destabilisation of the entire West Antarctic Ice Sheet

    Prelims Pointers

    • Thwaites Glacier is located in West Antarctica
    • Known as the Doomsday Glacier due to sea level rise potential
    • Complete melt could raise sea levels by about 65 cm
    • Study used satellite and GPS data over two decades
    • West Antarctic Ice Sheet is a global climate tipping element
    [2021] With reference to the water on the planet Earth, consider the following statements: 

    1. The amount of water in the rivers and lakes is more than the amount of groundwater

    2. The amount of water in polar ice caps and glaciers is more than the amount of groundwater

    Which of the statements given above is/are correct? 

    (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2

  • India’s progress on its climate targets

    Introduction

    India’s climate commitments under the Paris Agreement reflect the principle of Common but Differentiated Responsibilities, balancing development imperatives with environmental responsibility. While headline indicators show substantial compliance, deeper analysis reveals incomplete decoupling between growth and emissions, structural dependence on coal, and gaps between capacity creation and actual decarbonisation outcomes.

    Why in the News?

    India has recorded significant progress on climate metrics such as emissions intensity reduction and non-fossil power capacity expansion. Emissions intensity declined by nearly 36% between 2005 and 2020, placing India ahead of its 2030 target of 33-35% reduction. Installed non-fossil capacity crossed 40% of total capacity, achieving a Paris commitment nearly a decade early. However, absolute emissions continue to rise, forest carbon sinks remain overstated, and renewable capacity has not proportionally translated into electricity generation. The divergence between numerical targets and real climate outcomes makes this a critical inflection point.

    Has India Successfully Reduced Its Emissions Intensity?

    1. Emissions Intensity Reduction: Declined by approximately 36% from 2005 to 2020, exceeding the 2030 target of 33-35%.
    2. Comparative Performance: Intensity decline outperforms most G20 peers despite lower per-capita emissions.
    3. Structural Drivers: Renewable capacity expansion, efficiency improvements in power generation, and sectoral shifts towards services.
    4. Limitation: Intensity reduction masks rising absolute emissions due to economic expansion.

    Why Do Absolute Emissions Continue to Rise?

    1. Incomplete Decoupling: GDP growth has outpaced emissions growth, but emissions have not declined in absolute terms.
    2. Emission Levels: Territorial greenhouse gas emissions stood at ~2,959 MtCO₂e in 2020 and continue to increase.
    3. Sectoral Divergence: Power sector emissions grow faster than industrial emissions due to coal dependence.
    4. Policy Implication: Intensity-based targets delay hard choices on fossil fuel phase-down.

    Has Renewable Capacity Expansion Translated into Clean Power Generation?

    1. Installed Capacity: Non-fossil capacity crossed 40% by 2025, nearly ten years ahead of schedule.
    2. Generation Share: Non-fossil generation remains substantially lower due to grid constraints and intermittency.
    3. Coal Dominance: India retains 253 GW of coal-based capacity, providing baseload power.
    4. Curtailment Losses: Grid congestion and state-level regulatory bottlenecks limit renewable utilisation.
    5. Storage Gap: Against a projected requirement of 336 GWh of storage by 2029-30, only 500 MW of battery storage is operational as of September 2025.

    Are Forest-Based Carbon Sink Targets Credible?

    1. Official Claim: India reports 30.43 billion tonnes of CO₂ equivalent forest carbon stock.
    2. 2030 Target: Additional 2.5-3 billion tonnes CO₂e sequestration through forests.
    3. Measurement Issue: Forest Survey of India defines “forest cover” as land above one hectare with over 10% canopy, including plantations and monocultures.
    4. Satellite Evidence: Natural forest cover increased only 156 sq km between 2015-2023, while recorded forest cover rose by over 75,000 sq km.
    5. CAMPA Utilisation: Of ₹95,000 crore available, only 23% utilised between 2019-20 and 2023-24.
    6. Policy Risk: Over-reliance on plantations weakens biodiversity and long-term carbon stability.

    Why Does the Gap Persist Between Targets and Outcomes?

    1. Capacity vs Output Gap: Renewable installations do not proportionately increase clean electricity generation.
    2. Grid Infrastructure Deficit: Transmission, balancing capacity, and storage expansion lag behind capacity addition.
    3. Policy Fragmentation: Climate governance prioritises accounting compliance over ecological restoration.
    4. Administrative Frictions: Delays in land acquisition, approvals, and state coordination limit execution.

    What Are the Critical Challenges Ahead?

    1. Coal Lock-in: Continued investment in coal infrastructure constrains long-term decarbonisation.
    2. Storage Scaling: Energy transition hinges on rapid deployment of battery and pumped storage.
    3. Data Transparency: Overstated forest metrics undermine credibility of carbon sink commitments.
    4. Climate Stress: Rising heatwaves and water stress challenge forest productivity and carbon assimilation.

    Conclusion

    India has delivered on quantified climate commitments but remains short of achieving ecological transformation. The next phase requires shifting from intensity-led compliance to outcome-oriented decarbonisation through coal phase-down, grid modernisation, credible carbon accounting, and governance reform.

    PYQ Relevance

    [UPSC 2021] Describe the major outcome of the 26th session of the Conference of Parties [COP] to the United Nations Framework conversation on climate change [UNFCCC]. What are the commitments made by India in this conference.

    Linkage: This question links to the article’s evaluation of India’s COP-26 commitments, showing that while emissions intensity reduction and non-fossil capacity targets are being met, absolute emissions continue to rise. It highlights the UPSC focus on assessing climate pledges against actual outcomes, especially coal dependence and gaps in real decarbonisation.

  • Remarkable New Species Discovered in India in 2025

    Why in the News?

    In December 2025, Indian scientists announced the discovery of multiple new species across diverse ecosystems, ranging from the Eastern Himalayas to the Western Ghats, highlighting India’s rich and still underexplored biodiversity.

    Key New Species Discovered

    Bridgeoporus kanadii

    Type: Macro fungi
    Discovery region: West Kameng district, Arunachal Pradesh
    Habitat: Old growth Abies fir trees
    Key features:

    • Thick, leathery and massive fruiting body
    • Extremely sturdy, capable of bearing human weight
       Significance:
    • Indicates high fungal diversity in Eastern Himalayan forests
    • Highlights ecological value of old growth conifer ecosystems

    Rhinophis siruvaniensis

    Type: Non venomous shieldtail snake
     Family: Uropeltidae
     Discovery region: Siruvani Hills, Kerala, Western Ghats
     Key features:

    • Fossorial or burrowing lifestyle
    • Specialized tail shield for digging and protection
       Significance:
    • Adds to endemic reptile diversity of the Western Ghats
    • Reinforces the region as a global biodiversity hotspot

    Neelus sikkimensis

    Type: Springtail or Collembola
    Discovery region: High altitude cold desert soils of Sikkim, Eastern Himalayas
    Key features:

    • Wingless arthropod with a jumping organ called furcula
    • First record of the genus Neelus in India
       Significance:
    • Identified by Zoological Survey of India
    • Global species count of Neelus expanded to eight
    • Indicates biodiversity even in extreme cold environments

    Parasynnemellisia khasiana

    Type: Fungus
    Taxonomy: Completely new genus and species
    Discovery region: Khasi Hills near Mawsynram, Meghalaya
    Habitat: Dense bamboo forests in ultra high rainfall zones
    Key features:

    • Grows in association with bamboo ecosystems
    • Adapted to one of the wettest regions on Earth
       Significance:
    • Demonstrates unexplored microbial diversity of Northeast India

    Dolomedes indicus

    Type: Fishing spider
    Discovery region: Wayanad and Lakkidi, Western Ghats, Kerala
    Key features:

    • Semi aquatic spider
    • Can skate on water surfaces
    • Hunts aquatic insects and small fish

    Significance:

    • First confirmed fishing spider species in India
    • Highlights freshwater dependent arthropod diversity

    Ophiorrhiza mizoramensis

    Type: Flowering shrub
    Family: Rubiaceae or coffee family
    Discovery region: Murlen National Park, Mizoram
    Key features:

    • Grows up to one metre
    • Dark purplish pink tubular flowers
    • Unique stigma lobe structure

    Conservation status:

    • Provisionally assessed as Critically Endangered
    • Fewer than 200 mature individuals recorded

    Overall Significance

    • Confirms India as a megadiverse country
    • Highlights importance of Eastern Himalayas and Western Ghats
    • Strengthens case for habitat conservation and taxonomy research
    • Shows climate resilient and niche specific species evolution

    Prelims Pointers

    • Western Ghats and Eastern Himalayas are global biodiversity hotspots
    • New genus discovery indicates unexplored fungal diversity
    • High altitude ecosystems also host unique micro fauna
    • Many new species face immediate conservation threats
    [2022] With reference to ‘Gucchi’ sometimes mentioned in the news, consider the following statements: 

    1. It is a fungus. 

    2. It grows in some Himalayan forest areas

    3. It is commercially cultivated in the Himalayan foothills of north-eastern India

    Which of the statements given above is correct? 

    (a) 1 only (b) 3 only (c) 1 and 2 (d) 2 and 3

  • Barcelona Convention COP24 

    Why in the News?

    At COP24 of the Barcelona Convention held in Cairo, European Union countries and Mediterranean partners adopted strengthened commitments to protect the Mediterranean Sea from pollution and ecological degradation.

    About Barcelona Convention

    • A legally binding regional environmental agreement led by United Nations Environment Programme
    • Focuses on protection of the Mediterranean Sea and sustainable coastal management

    Key Milestones

    • Adopted on 16 February 1976 as Convention for the Protection of the Mediterranean Sea Against Pollution
    • Entered into force in 1978
    • Amended and renamed in 1995 as the Convention for the Protection of the Marine Environment and the Coastal Region of the Mediterranean

    About Mediterranean Sea

    • A semi enclosed intercontinental sea between Europe, Asia and Africa
    • Covers about 2.5 million square kilometres
    • Accounts for roughly 0.7 percent of global ocean area
    • Recognised as a global biodiversity hotspot

    Connectivity

    • Atlantic Ocean through Strait of Gibraltar
    • Black Sea through Dardanelles, Sea of Marmara and Bosporus
    • Red Sea through Suez Canal

    Prelims Pointers

    • Barcelona Convention is a regional sea convention under UNEP
    • Mediterranean Sea is semi enclosed making it vulnerable to pollution
    • COP is the supreme decision making body of the Convention
    • Integrated coastal zone management is a key protocol area
    [2017] Mediterranean Sea is a border of which of the following countries? 

    1. Jordan 

    2. Iraq 

    3. Lebanon 

    4. Syria 

    Select the correct answer using the code given below: 

    (a) 1, 2 and 3 only (b) 2 and 3 only (c) 3 and 4 only (d) 1, 3 and 4 only

  • Is Delhi’s winter pollution breeding superbugs?

    Introduction

    Delhi’s winter pollution is characterised by elevated particulate matter levels due to temperature inversion, biomass burning, vehicular emissions, and industrial activity. The Jawaharlal Nehru University (JNU) study identifies airborne bacteria attaching to fine particulates, enabling their survival, dispersal, and inhalation by humans. The findings indicate that environmental pollution is actively contributing to antimicrobial resistance, transforming air quality from a respiratory hazard into a microbial and genetic risk pathway.

    Why in the News?

    A Jawaharlal Nehru University (JNU) study, published in Nature, has for the first time in Delhi established the presence of antibiotic-resistant bacteria in ambient air, particularly during winter months. The study records high bacterial loads exceeding WHO exposure thresholds in crowded urban localities, establishing a direct association between particulate matter (PM2.5 and PM10) and airborne transmission of multi-drug resistant Staphylococci. This marks a departure from earlier AMR discourse that focused primarily on hospitals, water bodies, and food chains, by identifying air as a vector for AMR spread.

    How does air pollution facilitate the spread of antibiotic-resistant bacteria?

    1. Particulate Matter (PM2.5 and PM10): Facilitates bacterial adhesion, atmospheric transport, and prolonged suspension.
    2. Carrier Function: Enables bacteria to remain viable and reach human respiratory tracts.
    3. Toxic Synergy: Enhances inflammatory response and susceptibility to infection upon inhalation.
    4. Crowded Environments: Increases bacterial exchange through coughing and breathing.

    What did the JNU study reveal about bacterial load in Delhi’s air?

    1. First-of-its-kind Study: Conducted across indoor and outdoor environments in Delhi.
    2. High Bacterial Concentration: Levels exceeded WHO recommended exposure limit of 1000 CFU/m³.
    3. Seasonal Pattern: Winter and monsoon months recorded higher bacterial loads than summer.
    4. Urban Hotspots: Crowded neighbourhoods exhibited the highest concentrations.

    Which antibiotic-resistant bacteria were identified?

    1. Staphylococci Presence: Eight species identified in air samples.
    2. Dominant Species: Staphylococcus arlettae emerged as the most prevalent.
    3. Resistance Profile:
      1. 36% multi-drug resistant strains
      2. 73% resistance to at least one antibiotic
    4. Clinical Significance: Staphylococci cause pneumonia, sepsis, skin infections, and endocarditis.

    Which locations showed the highest bacterial load?

    1. High-Load Areas: Munirka Market Complex, Slum clusters near Vasant Vihar
    2. Low-Load Area: Jawaharlal Nehru University (STP site), attributed to lower population density
    3. Urban Pattern: Crowding directly correlated with bacterial concentration.

    Who is most vulnerable to airborne antibiotic-resistant bacteria?

    1. Elderly Population: Reduced immunity increases infection risk.
    2. Immunocompromised Individuals: Cancer survivors and patients with chronic illnesses.
    3. Urban Poor: Greater exposure due to overcrowding and limited healthcare access.
    4. Hospital Visitors: Risk of exposure to resistant strains circulating between hospital and community.

    How does improper antibiotic disposal worsen the AMR threat?

    1. Disposal Practices: Flushing or discarding antibiotics into municipal waste.
    2. Environmental Impact: Creates low-dose antibiotic environments enabling bacterial mutation.
    3. Resistance Amplification: Promotes survival and genetic evolution of resistant strains.
    4. Ecosystem Spread: Resistance genes transmitted across soil, water, air, and food chains.

    What gaps in AMR governance does the study highlight?

    1. Monitoring Deficit: Absence of systematic surveillance of airborne AMR.
    2. Urban Blind Spot: AMR strategies focused on hospitals and wastewater, not air.
    3. Data Fragmentation: Lack of integration between pollution control and health agencies.

    Conclusion

    The JNU study underscores that Delhi’s winter air pollution is not merely a respiratory hazard but an active enabler of antimicrobial resistance, facilitating the survival and spread of antibiotic-resistant bacteria through particulate matter. By revealing air as an overlooked transmission pathway for resistant microbes, the findings expose critical gaps in urban pollution control, waste disposal practices, and AMR surveillance frameworks. Addressing this emerging threat requires integrating air quality management with antimicrobial stewardship and environmental monitoring, without which urban public health risks will continue to intensify silently.

    PYQ Relevance

    [UPSC 2014] Can overuse and free availability of antibiotics without Doctor’s prescription, be contributors to the emergence of drug-resistant diseases in India? What are the available mechanisms for monitoring and control? Critically discuss the various issues involved.

    Linkage: This question directly links to GS Paper III under Public Health, Science & Technology, and Environmental Pollution, particularly the microtheme of Antimicrobial Resistance (AMR). Recent evidence, such as findings on airborne antibiotic-resistant bacteria in polluted urban environments, expands the AMR discourse beyond clinical misuse to environment-driven and community-level transmission.

  • Drones Used to Detect Virus in Arctic Whales 

    Why in the News?

    Scientists have detected Cetacean morbillivirus in Arctic waters for the first time by collecting breath samples from whales using drones.

    About the Study

    • Title Deep breath out molecular survey of selected pathogens in blow and skin biopsies from North Atlantic cetaceans
    • Published in BMC Veterinary Research
    • Lead researcher Helena Costa from Nord University

    Species and Regions Covered

    • Whale species studied Humpback whale, sperm whale and fin whale
    • Regions Northern Norway, Iceland and Cape Verde
    • Sample collection period 2022 to 2025
    • Over 50 whale blow samples collected

    About Cetacean Morbillivirus

    • Infectious virus affecting whales, dolphins and porpoises
    • First discovered in 1987
    • Impacts respiratory and nervous systems
    • Known to cause mass strandings and deaths
    • Spreads through direct contact and respiratory droplets

    Prelims Pointers

    • Whale blow refers to exhaled breath from blowholes
    • Drones are emerging tools in non invasive wildlife research
    • Cetacean morbillivirus is linked to mass marine mammal mortality events
    • Arctic disease surveillance is critical under climate change
    [2020] At the present level of technology, which of the above activities can be successfully carried out by using drones? 

    1. Spraying pesticides on a crop field 

    2. Inspecting the craters of active volcanoes 

    3. Collecting breath samples from spouting whales for DNA analysis 

    Select the correct answer using the code given below: 

    (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3

  • Why does India need climate resilient agriculture

    Introduction

    India’s food system faces mounting stress from climate variability, declining soil health, and environmental degradation. Agriculture must simultaneously ensure food security for a growing population and adapt to rising climate risks. Conventional farming systems, particularly in rainfed regions, are proving inadequate under these pressures. Climate-resilient agriculture offers a pathway to sustain productivity while safeguarding ecological stability.

    Why in the news?

    Climate-resilient agriculture has gained renewed attention as India confronts increasing climate unpredictability, declining soil health, and rising pressure on food security. With nearly 51% of India’s net sown area being rainfed and contributing about 40% of total food production, climate variability poses a systemic risk to agricultural output and farmer livelihoods. 

    Why is Climate-Resilient Agriculture Necessary for India?

    1. Rainfed Agriculture Dependence: Nearly 51% of India’s net sown area remains rainfed, producing about 40% of national food output, increasing vulnerability to rainfall variability.
    2. Climate Variability Exposure: Erratic monsoons, heat stress, droughts, and extreme weather events directly affect crop yields and farm incomes.
    3. Population Pressure: Rapid population growth intensifies demand for reliable and stable agricultural productivity.
    4. Limits of Conventional Farming: Input-intensive methods show declining returns under climate stress and contribute to soil degradation and pollution.

    What is Climate-Resilient Agriculture (CRA)?

    1. Biotechnology Integration: Uses biofertilisers, biopesticides, and soil-microbiome analysis to reduce chemical dependence while maintaining productivity.
    2. Genomic Interventions: Enables development of genome-edited crops tolerant to drought, heat, salinity, and pests.
    3. Digital and AI-Based Tools: Applies AI-driven analytics to integrate climate and agronomic variables for location-specific advisories.
    4. Sustainability Orientation: Balances productivity enhancement with soil health and environmental protection.

    Where Does India Stand Today on CRA Adoption?

    1. Institutional Leadership: In 2011, the Indian Council of Agricultural Research launched the National Innovations in Climate Resilient Agriculture (NICRA) project.
    2. Technology Demonstration: CRA practices demonstrated across 448 climate-resilient villages.
    3. Key Interventions Implemented:
      1. Cropping Techniques: System of Rice Intensification (SRI), aerobic rice cultivation.
      2. Resource Efficiency: Zero-till wheat sowing, direct seeding of rice.
      3. Soil Management: In-situ incorporation of rice residues.
    4. Outcome: Enhanced adaptive capacity and resilience of farmers to climate variability.

    How Does the National Mission for Sustainable Agriculture Contribute?

    1. Productivity Enhancement: Focuses on improving yields, especially in rainfed regions.
    2. Integrated Farming Systems: Encourages crop-livestock-resource integration.
    3. Water Use Efficiency: Prioritises efficient irrigation and moisture conservation.
    4. Soil Health Management: Supports balanced nutrient use and organic matter restoration.
    5. Resource Synergy: Aligns conservation with productivity goals.

    What is the Role of Biotechnology and BioE3 Policy in CRA?

    1. Policy Positioning: BioE3 policy identifies CRA as a key thematic area for biotechnology-led solutions.
    2. Commercial Readiness: Several CRA-relevant technologies already commercialised.
    3. Bio-inputs Expansion: Companies supplying bio-inputs that improve soil health and reduce chemical dependency.
    4. Private Sector Participation: Signals transition from pilot-based models to scalable solutions.

    How is Digital Agriculture Strengthening Climate Resilience?

    1. AI-Enabled Advisory Services: Provide real-time, location-specific climate advisories.
    2. Precision Irrigation: Optimises water use under variable climatic conditions.
    3. Crop Health Monitoring: Enables early detection of stress and pest outbreaks.
    4. Yield Prediction Tools: Improve risk assessment and planning for farmers.

    Conclusion

    Climate-resilient agriculture is no longer optional for India’s food system. High dependence on rainfed farming, combined with climate volatility, necessitates a coordinated national strategy integrating biotechnology, digital tools, and institutional support. India’s early investments through NICRA, sustainable agriculture missions, and biotechnology policies provide a foundation, but scaling and coherence remain critical for long-term resilience.

    PYQ Relevance

    [UPSC 2016] Given the vulnerability of Indian agriculture to vagaries of nature, discuss the need for crop insurance and bring out the salient features of the Pradhan Mantri Fasal Bima Yojana (PMFBY). 

    Linkage: This question directly links to GS Paper III themes of agricultural vulnerability, climate risk, and risk-mitigation mechanisms. Climate-resilient agriculture frameworks emphasize crop insurance (PMFBY) as a financial resilience tool to buffer farmers against increasing climate-induced crop losses.

  • Amazonian Stingless Bees 

    Why in the News?

    Municipalities in Peru passed a landmark ordinance granting legal rights to Amazonian stingless bees, making them the first insects in the world to receive such recognition.

    About Amazon’s Stingless Bees

    Stingless bees belong to the Meliponini group and either lack stingers or have non functional stingers, making them harmless to humans. They are critical pollinators in tropical ecosystems.

    Origin

    • Among the oldest bee lineages, existing for nearly 80 million years
       • Emerged during the age of dinosaurs
       • About 500 species globally, nearly half in the Amazon

    Habitat

    • Tropical forests worldwide
       • Highly abundant in the Amazon rainforest
       • Peru hosts over 170 species

    Key Ecological and Cultural Features

    • Primary rainforest pollinators
       • Pollinate over 80 percent of Amazonian plant species
       • Support key global crops like coffee, cacao, avocado, blueberry
       • Deeply embedded in Indigenous knowledge systems
       • Culturally significant to communities such as Asháninka and Kukama-Kukamiria

    Legal Rights for Stingless Bees

    The ordinance recognises inherent rights, including
     • Right to exist and flourish
     • Right to maintain healthy populations
     • Right to regenerate natural ecological cycles
     • Right to live in pollution free habitats
     • Right to legal representation when threatened

    Significance

    • Global legal first: First instance of insects granted legal rights
       • Stronger conservation framework: Enables legal action against deforestation, pollution, and habitat loss
       • Advances Rights of Nature doctrine: Moves from human centred environmental protection to ecosystem centred justice
    [2023] Which of the following organisms perform waggle dance for others of their kin to indicate the direction and the distance to a source of their food? 

    (a) Butterflies 

    (b) Dragonflies 

    (c) Honeybees 

    (d) Wasps

  • Secondary Pollutants

    Why in the News?

    A recent analysis by the Centre for Research on Energy and Clean Air has revealed that secondary pollutants now contribute nearly one third of Delhi’s annual PM2.5 load, highlighting a major shift in the nature of urban air pollution.

    What are Secondary Pollutants?

    • Secondary pollutants are not emitted directly from pollution sources.
    • They are formed in the atmosphere when primary pollutants such as SO₂, NOx and VOCs undergo chemical reactions.
    • These reactions are influenced by sunlight, temperature, humidity and stagnant air conditions.
    • They often accumulate downwind and over time, making monitoring and control more complex than primary pollutants.

    Major Secondary Pollutants

    • Secondary PM2.5: Ammonium sulfate and Ammonium nitrate
    • Ozone (O₃): Formed from nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight
    • Acids: Sulfuric acid and Nitric acid (contributors to acid rain)
    • Photochemical smog components: Peroxyacetyl nitrates (PANs) and Nitrogen dioxide (NO₂)

    Implications

    Regional and transboundary impact

    • Secondary aerosols can travel hundreds of kilometres
    • Delhi’s air quality is influenced by emissions from coal intensive states beyond the NCR

    Winter smog intensification

    • Moist and stagnant winter air sharply increases secondary PM2.5

    Health risks

    • Fine secondary particles penetrate deep into the lungs
    • Increase risks of respiratory and cardiovascular diseases

    Prelims Pointers

    • Secondary pollutants are formed in the atmosphere, not emitted directly
    • Ammonia plays a key role in secondary PM2.5 formation
    • Winter meteorology is crucial for secondary aerosol build up
    • Air pollution control requires regional coordination, not only city level measures
    [2013] Photochemical smog is a resultant of the reaction among 

    (a) NO₂, O₃ and peroxyacetyl nitrate in the presence of sunlight

    (b) CO₂, O₂, and peroxyacetyl nitrate in the presence of sunlight

    (c) CO, CO₂, and NO₂ at low temperature

    (d) high concentration of NO₂, O₃ and CO in the evening

  • Kolleru Lake

    Why in the News?

    • Kolleru Lake is gaining recognition for its black dried fish, now popular in domestic and international markets.

    What is Black Dried Fish

    • A traditional sun dried fish product
    • Prepared by drying small freshwater or brackish water fish without heavy salting
    • Dark colour develops due to natural oxidation and fermentation during drying
    • Strong aroma and long shelf life

    Location and Physical Features

    • One of the largest freshwater lakes in India
    • Located in Andhra Pradesh, near Eluru
    • Lies in the inter-deltaic plain of Krishna and Godavari
    • Acts as a natural flood-balancing reservoir for both rivers
    • Shallow lake in nature

    Hydrology

    • Receives water from Budameru, Ramileru, Tammileru, Errakalva rivers
    • Also fed by 18 drains
    • Drains into the Bay of Bengal through Upputeru outlet

    Ecological Importance

    • Known as Peerless Fisherman’s Paradise and Bird Heaven
    • Declared a Wildlife Sanctuary in November 1999
    • Designated a Ramsar Wetland in November 2002
    • Supports over 20 million migratory birds annually
    • Key species: Grey pelican, Painted stork, Open billed stork
    • Hosts migratory birds from Siberia, Central Asia, and the Himalayas

    Socio-Economic Significance

    • Sustains livelihoods through fishing, duck farming, and paddy cultivation
    • Traditional black dried fish is a unique local product with growing market value

    Prelims Pointers

    • Largest freshwater lake in Andhra Pradesh
    • Ramsar site and wildlife sanctuary
    • Flood moderation role for Krishna and Godavari
    • Internationally known for migratory birds and fisheries
    Consider the following statements: (2023)

    1. Jhelum River passes through Wular Lake. 

    2. Krishna River directly feeds Kolleru Lake. 

    3. Meandering of Gandak River formed Kanwar Lake. 

    How many of the statements given above are correct? 

    (a) Only one (b) Only two (c) All three (d) None