From choking cities to rising seas — the biological basis of environmental problems and their solutions. This chapter covers pollution (air, water, solid waste, agro-chemicals, radioactive), global warming, ozone depletion, and deforestation.
Before diving in, here's the entire chapter on one page. Environmental issues arise from pollution (air, water, waste), global phenomena (greenhouse, ozone), and deforestation.
Environmental issues result from human activities that pollute air, water, and land. Air pollution (CO, SO₂, NOx, particulates) causes respiratory problems and acid rain. Water pollution (sewage, industrial effluents, thermal) harms aquatic life. Greenhouse gases (CO₂, CH₄, CFCs) warm the planet. CFCs destroy the ozone layer. Deforestation causes soil erosion and reduces biodiversity. Solutions include pollution control, renewable energy, afforestation, and international agreements (Montreal, Kyoto, Paris).
Select the likely source of each pollutant.
Air pollution: The addition of any substance or form of energy to the atmosphere that harms human health, other organisms, or the environment.
Pollutants: The substances that cause pollution. Can be solid, liquid, or gas.
Sources:
| Pollutant | Source | Effects |
|---|---|---|
| Carbon monoxide (CO) | Incomplete combustion, vehicles, cigarettes | Binds hemoglobin ~200× more strongly than O₂ → carboxyhemoglobin → reduces O₂ transport. Headache, dizziness, death at high levels. |
| Carbon dioxide (CO₂) | Respiration, fossil fuel burning, deforestation | Greenhouse gas — global warming. Not directly toxic, but climatic effects. |
| Sulfur dioxide (SO₂) | Burning coal (power plants), smelting | Respiratory irritation, aggravates asthma. Acid rain (H₂SO₄). Damages plants, buildings. |
| Nitrogen oxides (NOx) | Vehicle exhaust, power plants, lightening | Respiratory problems, acid rain (HNO₃), photochemical smog. NO₂ is brown. |
| Ozone (O₃) | Photochemical reactions between NOx and hydrocarbons | Ground-level ozone is toxic — damages lungs, plants. (But stratospheric ozone is protective!) |
| Hydrocarbons | Vehicle exhaust, solvents | Some are carcinogenic (benzene). Contribute to photochemical smog. |
| Particulate matter (PM) | Dust, smoke, industrial processes | PM2.5 (fine) and PM10 — penetrate deep into lungs, cause asthma, bronchitis, cancer. |
| Heavy metals | Industries, mining | Lead, mercury, cadmium, arsenic — toxic, affect nervous system, kidneys. |
Smog: A combination of smoke and fog — severe air pollution that reduces visibility.
Two types:
Acid rain: Rain with pH below 5.6 (naturally, rain is slightly acidic due to CO₂ forming H₂CO₃, pH ~5.6).
Causes: SO₂ and NOx from burning fossil fuels react with water vapor and oxygen in the atmosphere:
SO₂ + O₂ + H₂O → H₂SO₄ (sulfuric acid)
NOx + H₂O → HNO₃ (nitric acid)
Effects:
Control: Reduce SO₂ and NOx emissions; use scrubbers in factories; use cleaner fuels.
Air pollution: CO (carboxyhemoglobin), SO₂/NOx (acid rain), O₃ (ground-level toxic), particulates (respiratory), hydrocarbons (carcinogenic). Smog (classical = London, photochemical = LA). Acid rain (pH <5.6) damages lakes, forests, buildings. Control: electrostatic precipitators, scrubbers, catalytic converters, cleaner fuels, afforestation.
Water pollution: The addition of any substance or form of energy to water that harms human health, aquatic organisms, or water quality.
Major sources:
1. Sewage pollution:
2. Industrial pollution:
3. Agricultural pollution:
4. Thermal pollution:
5. Oil spills:
Eutrophication: Nutrient enrichment of a water body (especially by nitrogen and phosphorus).
Steps:
Consequences: Loss of aquatic life, unusable water, bad smell, loss of biodiversity.
Example: Dal Lake (Srinagar) is threatened by eutrophication. Many rivers and lakes near cities are eutrophic.
BOD (Biological Oxygen Demand): The amount of oxygen consumed by bacteria to decompose organic matter in water (measured over 5 days at 20°C, expressed in mg/L).
Significance: Higher BOD = more organic pollution = more oxygen consumed. Clean water has low BOD (~1 mg/L). Polluted water has high BOD (>10 mg/L).
COD (Chemical Oxygen Demand): The amount of oxygen needed to chemically oxidize all organic matter (using strong oxidant like K₂Cr₂O₇). Includes material that BOD doesn't (unbiodegradable organics).
Water quality standard: Drinking water BOD <2 mg/L; bathing water <3 mg/L.
Biomagnification (biological magnification): The increase in concentration of a toxic substance (pesticide, heavy metal) as it moves up the food chain.
Mechanism:
Example: DDT in food chain: water (0.003 ppb) → plankton (0.04 ppm) → small fish (0.5 ppm) → large fish (2 ppm) → fish-eating birds (25 ppm) → concentration increased 8 million times!
Effects: DDT caused eggshell thinning in birds (nearly wiped out bald eagles, peregrine falcons). Mercury caused Minamata disease in Japan.
Note: Biomagnification occurs with fat-soluble (lipophilic) substances that are not easily metabolized or excreted.
Water pollution: sewage (pathogens, BOD), industrial (heavy metals), agricultural (fertilizers, pesticides), thermal (hot water), oil spills. Eutrophication: nutrient enrichment → algal bloom → oxygen depletion → fish kill. BOD = biological oxygen demand (higher = more pollution). Biomagnification = increasing toxin concentration up food chain (DDT, mercury). Control: sewage treatment, effluent treatment, organic farming.
Solid waste: Discarded solid materials from households, industries, agriculture, hospitals, and other sources.
Types:
Solid waste management: The collection, transport, processing, and disposal of solid waste in an environmentally and economically sound manner.
Methods:
3Rs: Reduce, Reuse, Recycle
Plastic waste: Non-biodegradable, persists for centuries.
Problems:
Solutions:
Solid waste: municipal, industrial, biomedical, construction, e-waste, agricultural. Management: sanitary landfill, incineration, composting, vermicomposting, recycling. 3Rs — Reduce, Reuse, Recycle. Plastic is non-biodegradable, causes serious problems. India generates 62 MT/year; only 20% treated. Ban on single-use plastics from 2022.
Agro-chemicals: Chemicals used in agriculture to increase production — fertilizers, pesticides, herbicides, fungicides.
Benefits: Increased yield (Green Revolution), pest control.
Problems: Environmental pollution, biomagnification, resistance in pests.
Fertilizers: Provide essential plant nutrients — nitrogen (N), phosphorus (P), potassium (K), plus trace minerals.
Problems:
Solution: Organic farming, precision agriculture, slow-release fertilizers.
Pesticides: Chemicals used to kill pests — insects (insecticides), weeds (herbicides), fungi (fungicides), rodents (rodenticides).
Types:
Problems:
Biological control: Using natural enemies (predators, parasites, pathogens) to control pests — an alternative to chemical pesticides.
Examples:
Advantages: Eco-friendly, specific to pests, no biomagnification.
Limitations: Slower than chemicals, requires knowledge and management.
IPM: A balanced approach that combines biological, cultural, physical, and (as a last resort) chemical control methods to manage pests economically and sustainably.
Components:
Benefit: Reduces chemical use, protects environment, prevents resistance.
Agro-chemicals: fertilizers (N, P, K) cause eutrophication, nitrate pollution, N₂O emissions. Pesticides (organochlorines, organophosphates, etc.) cause biomagnification, pest resistance, non-target effects. Alternatives: biological control (Trichogramma, Bacillus thuringiensis, ladybugs, neem), IPM, organic farming.
Radioactive waste: Waste containing radioactive materials — from nuclear power plants, research, medical use, defense.
Sources:
1. Low-level waste (LLW): Low radioactivity — lab coats, gloves, tools, hospital waste. Short half-life (usually). Can be disposed in shallow burial.
2. Intermediate-level waste (ILW): Higher radioactivity — reactor components, chemical sludges. Requires shielding.
3. High-level waste (HLW): Spent nuclear fuel — extremely radioactive, long-lived (thousands of years). Requires deep geological disposal.
Safe disposal strategies:
Ideal geological sites: Salt mines, clay, granite — stable, impermeable.
Problems: Waste remains radioactive for thousands of years. No permanent disposal facility fully operational globally. Risk of leakage.
Radioactive waste: low, intermediate, high level. Sources: nuclear plants, weapons, medical, research. Disposal: storage, deep geological disposal, reprocessing, dilute and disperse, delay and decay. HLW requires isolation for thousands of years. Onkalo (Finland) is first operational deep repository.
Greenhouse effect: The warming of Earth's surface due to greenhouse gases trapping heat in the atmosphere.
How it works:
Natural greenhouse effect: Keeps Earth warm (~15°C average, without it would be −18°C). Essential for life.
Enhanced greenhouse effect: Human activities add extra greenhouse gases → extra warming → global warming.
| Gas | Source | Relative Contribution | Global Warming Potential (GWP) |
|---|---|---|---|
| Carbon dioxide (CO₂) | Fossil fuel burning, deforestation, respiration | ~60% | 1 (reference) |
| Methane (CH₄) | Rice paddies, livestock (cows), wetlands, landfills, natural gas leaks | ~20% | ~25× |
| Nitrous oxide (N₂O) | Fertilizers, industrial processes, biomass burning | ~6% | ~300× |
| CFCs (chlorofluorocarbons) | Refrigerants, propellants, foam blowing | ~14% | ~5,000–14,000× |
| Water vapor (H₂O) | Evaporation (natural) | Largest natural | — |
Note: CFCs are both greenhouse gases AND ozone-depleting. Banned under Montreal Protocol.
Global warming: The observed increase in Earth's average surface temperature due to enhanced greenhouse effect.
Evidence:
Consequences of global warming:
Paris Agreement (2015): Nearly all countries committed to limit global warming to well below 2°C (ideally 1.5°C) above pre-industrial levels.
Greenhouse effect: natural warming (~15°C vs −18°C without). Enhanced by human emissions of CO₂, CH₄, N₂O, CFCs. Global warming (~1.1°C rise since 1880): melting ice, sea level rise, extreme weather, ecosystem disruption. Control: reduce emissions, renewables, afforestation, CCS, international agreements (Kyoto, Paris).
Ozone (O₃): A gas composed of three oxygen atoms. Found in two places:
Stratospheric ozone: ~90% of atmospheric ozone. Continuously formed and destroyed by UV light:
O₂ + UV → 2O
O + O₂ → O₃
O₃ + UV → O₂ + O
This cycle absorbs most UV-B (280-320 nm) and UV-C (<280 nm) — protects life.
Ozone depletion: The thinning of the stratospheric ozone layer due to human-made chemicals (especially CFCs).
Causes:
Ozone hole: Severe seasonal thinning of the ozone layer — most pronounced over Antarctica.
Why Antarctica?
Discovery: 1985 — Joe Farman, Brian Gardiner, Jonathan Shanklin (British Antarctic Survey) reported massive ozone thinning over Antarctica. Led to global action.
Size: The Antarctic ozone hole (Sept-Oct) — ~20-25 million km² (larger than North America!).
Harmful UV-B radiation reaches Earth:
Montreal Protocol (1987): International treaty to phase out ozone-depleting substances (CFCs, halons, HCFCs, methyl bromide).
Success:
India: Phased out CFCs by 2010; currently phasing out HCFCs (by 2030).
Ozone (O₃) in stratosphere protects from UV. CFCs destroy ozone via Cl radical chain — 1 Cl destroys 100,000 O₃. Ozone hole (Antarctica) — severe thinning discovered 1985. Effects: skin cancer, cataracts, ecosystem damage. Montreal Protocol (1987) phased out CFCs — ozone layer recovering, expected healed by 2066.
Deforestation: The large-scale removal of trees from forests — usually for agriculture, urbanization, or logging.
Causes:
Consequences:
Solutions:
Soil erosion: Removal of topsoil by wind or water. Topsoil is the most fertile layer — its loss reduces crop yield.
Causes:
Desertification: The process of fertile land becoming desert — caused by drought, deforestation, overgrazing, poor irrigation.
Examples of desertification: Thar desert expanding (Rajasthan), Sahel region (Africa), parts of China.
Prevention:
Indigenous peoples: Forest-dwelling communities — tribal groups in India, Amazon tribes, etc.
Problems from deforestation:
Solutions: Recognize tribal land rights, community-based forest management, biodiversity conservation that respects indigenous rights.
JFM (India): A program that involves local communities in the management and protection of forests.
Key features:
Benefits: Reduced deforestation, improved forest cover, better livelihoods, reduced conflict.
Example: Arabari project (West Bengal, 1971) — one of the earliest successful community forest management projects.
Improper resource utilisation: Using resources wastefully, causing degradation.
Examples:
Deforestation: loss of biodiversity, climate change, soil erosion, desertification, floods, loss of livelihoods. Solutions: afforestation, reforestation, JFM, protected areas. Soil erosion — topsoil loss from wind/water — leads to desertification. Prevention: contour plowing, terrace farming, windbreaks. JFM involves communities — successful in India. Resource over-exploitation (fishing, grazing, groundwater) causes depletion.
"CO-CO₂-SO₂-NOx"
Carbon monoxide, Carbon dioxide, Sulfur dioxide, Nitrogen oxides — major air pollutants.
"CO binds Hemoglobin 200× more than O₂"
Form carboxyhemoglobin → less O₂ transport → headache, death.
"London = Coal + Fog (Classical)"
"Los Angeles = Sunlight + NOx (Photochemical)"
"SO₂ → H₂SO₄, NOx → HNO₃"
Sulfur and nitrogen oxides → strong acids → acid rain (pH <5.6).
"SIATAO"
Sewage, Industrial, Agricultural, Thermal, Oil spills.
"BOD = Biological (bacteria)", COD = Chemical (oxidants)"
BOD measures microbial oxygen consumption (5 days at 20°C). COD uses strong chemical oxidant.
"DDT, Mercury, PCBs"
Fat-soluble pollutants that bioaccumulate: DDT (banned), Mercury (Minamata), PCBs (banned).
"CO₂-CH₄-N₂O-CFCs"
Carbon dioxide (60%), Methane (20%), Nitrous oxide (6%), CFCs (14%).
"CFCs > N₂O > CH₄ > CO₂"
CFCs (5000-14000×) most potent, CO₂ reference (1).
"Cl· + O₃ → ClO· + O₂"
Cl radical destroys O₃. Then ClO· + O → Cl· + O₂ regenerates Cl → cycle repeats. 1 Cl destroys 100,000 O₃.
"1987 — Montreal — CFCs banned"
Most successful environmental treaty. All 197 countries ratified.
"Bio-Climate-Soil-Water-People"
Loss of biodiversity, climate change, soil erosion, floods, loss of livelihoods.
"Joint Forest Management — Started 1990, West Bengal first"
Communities + forest department jointly manage forests.
Use "CO-CO₂-SO₂-NOx" for air pollutants, "London coal, LA sunlight" for smog types, "SIATAO" for water pollution types, "CO₂-CH₄-N₂O-CFCs" for greenhouse gases, "Cl· destroys O₃" for ozone depletion.
Q1. Why is CO more dangerous than CO₂?
CO binds to hemoglobin to form carboxyhemoglobin. It has ~200× more affinity for hemoglobin than O₂. This reduces the oxygen-carrying capacity of blood — can lead to suffocation, headache, dizziness, and death at high concentrations.
CO₂ is a normal product of respiration. It's not directly toxic at normal concentrations but contributes to greenhouse effect (global warming). At very high concentrations, it causes respiratory issues.
Q2. What is acid rain? Mention two harmful effects.
Acid rain is rain with pH below 5.6 (normal rain is slightly acidic due to CO₂, pH ~5.6). It forms when SO₂ and NOx (from burning fossil fuels) react with water vapor and oxygen in the atmosphere to form H₂SO₄ and HNO₃, which fall as acid rain.
(1) Kills aquatic life: Acidifies lakes, kills fish (pH below 5 kills most)
(2) Damages forests: Leaches nutrients from soil, damages leaves
(3) Corrodes buildings: Attacks marble, limestone (e.g., Taj Mahal)
(4) Contaminates drinking water — heavy metals leached into water
Q3. What is eutrophication? How does it affect aquatic life?
Eutrophication = nutrient enrichment of a water body — especially by nitrogen and phosphorus from sewage, fertilizers, and detergents.
(1) Nutrients enter → algal bloom (rapid growth of algae)
(2) Algae die and decompose → microbial decomposition uses up oxygen
(3) Oxygen depleted → fish and aerobic life suffocate
(1) Fish and other oxygen-dependent organisms die (suffocation)
(2) Loss of biodiversity (only anaerobic organisms survive)
(3) Water becomes foul-smelling, green, unusable
(4) Foul taste, toxins from algal bloom may harm animals/humans
Example: Dal Lake (Srinagar) is threatened by eutrophication.
Q4. What is biological magnification? Give one example.
Biological magnification (biomagnification) = the increase in concentration of a toxic substance (pesticide, heavy metal) as it moves up the food chain.
(1) Toxic substance (fat-soluble) enters water/soil
(2) Absorbed by small organisms — not easily excreted (stored in fat)
(3) Eaten by fish → concentration increases
(4) Eaten by larger fish → further increase
(5) Eaten by birds/humans → highest concentration
DDT in aquatic food chain:
Water (0.003 ppb) → Plankton (0.04 ppm) → Small fish (0.5 ppm) → Large fish (2 ppm) → Fish-eating birds (25 ppm)
Concentration increased ~8 million times! Result: DDT caused eggshell thinning in birds (nearly extinct bald eagles).
Another example: Mercury → Minamata disease in Japan (neurological damage from eating contaminated fish).
Q5. What is global warming? What are its causes, effects, and control measures?
Global warming = the observed increase in Earth's average surface temperature due to enhanced greenhouse effect (human activities adding greenhouse gases).
Greenhouse gases absorb infrared radiation emitted by Earth's surface, trap heat:
(1) CO₂ — fossil fuel burning, deforestation (~60% of greenhouse effect)
(2) CH₄ — rice paddies, livestock, wetlands, landfills (~20%)
(3) N₂O — fertilizers, biomass burning (~6%)
(4) CFCs — refrigerants, propellants (~14%)
Earth's temp has risen ~1.1°C since pre-industrial times.
(1) Melting glaciers/ice caps → sea level rise (~21 cm since 1880)
(2) Coastal flooding: Maldives, Bangladesh threatened
(3) Extreme weather: Heatwaves, floods, droughts
(4) Coral bleaching — corals expel symbiotic algae
(5) Species migration — some go extinct (can't adapt)
(6) Spread of diseases — malaria, dengue expand range
(7) Agricultural losses — reduced crop yields
(8) Water scarcity — less glacier-fed river flow
(1) Reduce emissions: Renewables (solar, wind, hydro, nuclear)
(2) Energy efficiency: LEDs, efficient vehicles
(3) Afforestation: Trees absorb CO₂
(4) Reduce deforestation
(5) Reduce methane: Better livestock management, landfill gas capture
(6) CCS: Carbon capture and storage
(7) International agreements: Kyoto Protocol (1997), Paris Agreement (2015) — limit warming to 2°C
(8) Individual actions: Reduce consumption, use public transport
Selected exercise questions from the OLD NCERT Chapter (Environmental Issues). Removed from current syllabus but useful for competitive exams.
Constituents of domestic sewage: Human waste (feces, urine), kitchen waste, detergents, soaps, paper, organic matter, pathogens (bacteria, viruses, protozoa).
Effects of sewage on river:
(1) Pathogens: Disease-causing microbes → cholera, typhoid, dysentery, hepatitis.
(2) BOD increase: Organic matter decomposed by bacteria → oxygen consumed → oxygen level drops.
(3) Eutrophication: Nutrients (N, P) from detergents → algal blooms → more oxygen depletion → fish death.
(4) Foul smell: Anaerobic decomposition produces H₂S, CH₄ → foul odor.
(5) Water unusable — for drinking, bathing, irrigation.
Wastes: Plastic bags/bottles, paper, food waste, e-waste (batteries, old phones), construction waste, biomedical waste (if applicable), metal cans, glass bottles, tetra packs, wrappers.
Measures to reduce:
(1) Reduce: Use cloth bags, refillable bottles, avoid single-use plastic.
(2) Reuse: Reuse containers, bags, clothes.
(3) Recycle: Separate recyclable waste, compost organic waste.
(4) Segregate at source: Separate wet/dry waste.
(5) Compost: Organic waste → compost for plants.
(6) E-waste: Give to authorized recyclers.
(7) Avoid food waste: Take only what you need, compost leftovers.
(8) Support local recycling — buy products with recycled content.
Causes of water pollution:
(1) Sewage: Domestic waste — pathogens, organic matter, detergents.
(2) Industrial effluents: Chemicals, heavy metals (mercury, lead, arsenic), dyes, acids, alkalis.
(3) Agricultural runoff: Fertilizers (nitrates, phosphates), pesticides (DDT), animal waste.
(4) Thermal pollution: Hot water from power plants.
(5) Oil spills — from tankers, rigs.
(6) Radioactive waste — from nuclear plants.
Making water safe for drinking after sewage treatment:
(1) Primary treatment: Physical — screening, sedimentation (removes large debris and suspended solids).
(2) Secondary treatment: Biological — activated sludge process (bacteria decompose organic matter).
(3) Tertiary treatment: Chemical — precipitation of nutrients, filtration, disinfection.
(4) Disinfection: Chlorination, UV treatment, or ozonation to kill remaining pathogens.
(5) Quality testing: For pathogens, BOD, heavy metals before use.
Biomagnification (biological magnification): The increase in concentration of a toxic substance (pesticide, heavy metal) as it moves up the food chain.
How it affects humans: Humans are at the top of the food chain. When we eat contaminated fish, meat, or crops, we receive the highest concentrations of toxic substances. Effects include:
(1) Cancer (from DDT, PCBs)
(2) Neurological damage (from mercury — Minamata)
(3) Kidney damage (from cadmium — Itai-itai)
(4) Endocrine disruption (from pesticides)
(5) Reproductive problems
Example — DDT: Water (0.003 ppb) → Plankton (0.04 ppm) → Small fish (0.5 ppm) → Large fish (2 ppm) → Fish-eating birds (25 ppm). Concentration increased ~8 million times. Caused eggshell thinning in birds (nearly extinct bald eagles).
Greenhouse effect: The warming of Earth's surface because certain gases in the atmosphere (CO₂, CH₄, N₂O, water vapor, CFCs) trap the infrared radiation emitted by Earth's surface and re-emit it toward Earth.
Natural greenhouse effect: Without it, Earth's average temperature would be −18°C (too cold for life). With it, Earth is ~15°C (habitable). So the greenhouse effect is natural and essential.
Role in global warming: Human activities (burning fossil fuels, deforestation, agriculture) increase the concentration of greenhouse gases. This enhances the natural greenhouse effect → more heat trapped → global warming.
Main greenhouse gases:
(1) CO₂ — most important (60%) — fossil fuels, deforestation
(2) CH₄ — 20% — rice, livestock, wetlands
(3) N₂O — 6% — fertilizers, burning
(4) CFCs — 14% — refrigerants (banned by Montreal Protocol)
Major causes:
(1) Conversion to agricultural land (slash-and-burn, plantations)
(2) Urbanization (cities, roads, infrastructure)
(3) Logging — timber, fuelwood
(4) Mining
(5) Dams and highways
(6) Forest fires
(7) Cattle ranching
Consequences:
(1) Loss of biodiversity — tropical rainforests (highest biodiversity) lose species → extinction.
(2) Climate change — forests are carbon sinks; deforestation releases CO₂ → global warming.
(3) Soil erosion — tree roots hold soil; removal → erosion by wind/water.
(4) Desertification — dry land becomes desert.
(5) Floods — less water absorbed → runoff → flooding.
(6) Reduced rainfall — less transpiration.
(7) Loss of tribal livelihoods — forest-dependent communities displaced.
(8) Loss of ecosystem services — clean air, water, soil fertility.
Effects of ozone depletion:
(1) Skin cancer — non-melanoma and melanoma (increased by UV-B exposure).
(2) Cataracts — clouding of eye lens → blindness.
(3) Suppressed immune system — more susceptible to infections.
(4) Sunburn and premature aging.
(5) Damage to plants — reduced photosynthesis, crop yields.
(6) Damage to phytoplankton — base of marine food chain → impacts whole ecosystem.
(7) Damage to materials — plastics, paints degraded.
Montreal Protocol (1987):
International treaty to phase out ozone-depleting substances (CFCs, halons, HCFCs, methyl bromide, carbon tetrachloride).
Key points:
(1) Ratified by all 197 UN member countries
(2) Considered most successful environmental treaty
(3) CFC production cut by 99% since 1987
(4) Ozone layer recovering — expected to heal by 2066 (Antarctica)
(5) Kigali Amendment (2016) — phase down HFCs (greenhouse gases used as CFC replacements)
(6) India: phased out CFCs by 2010, HCFCs by 2030.
Causes:
(1) Deforestation — loss of tree roots that hold soil
(2) Overgrazing — livestock eat vegetation, expose soil
(3) Improper farming — deep plowing, no cover crops, monoculture
(4) Wind and water — natural erosion accelerated by human activity
(5) Construction — land clearing for buildings, roads
Effects:
(1) Loss of topsoil — most fertile layer gone → reduced crop yield
(2) Desertification — land becomes desert
(3) Water pollution — eroded soil clogs rivers, causes sedimentation in reservoirs
(4) Floods — less water absorption
(5) Loss of biodiversity — plants and animals lose habitat
Prevention measures:
(1) Contour plowing — plow along the contour to slow water runoff
(2) Terrace farming — steps on hillsides
(3) Strip cropping — alternate strips of crops
(4) Windbreaks — rows of trees planted as barriers
(5) Cover crops — crops that cover the soil
(6) Reduced tillage — no-till farming
(7) Afforestation
(8) Managed grazing — limit animals per area, rotate grazing
JFM (Joint Forest Management): A program in India (started 1990) that involves local communities (especially tribal) in the management and protection of forests.
Role in forest conservation:
(1) Community involvement: Forest department + local communities jointly manage forests.
(2) Incentive: Communities get access to minor forest products (fuelwood, fodder, honey, medicinal plants).
(3) Protection: Community protects forest from illegal logging, fire, encroachment.
(4) Livelihood: Provides sustainable income → reduces pressure on forests.
(5) Conflict resolution: Reduces conflict between forest department and communities.
(6) Biodiversity: Protected forests support wildlife.
Success: Started in Arabari (West Bengal, 1971). Now covers ~25% of India's forest area. Notable success stories — improved forest cover, better livelihoods.
Main sources of air pollution:
(1) Burning of fossil fuels (coal, petrol, diesel) — CO, CO₂, SO₂, NOx, hydrocarbons, particulates.
(2) Vehicles — CO, NOx, hydrocarbons, PM.
(3) Industries — SO₂, NOx, heavy metals, particulates.
(4) Burning of biomass — smoke, CO, CO₂.
(5) Agriculture — methane, ammonia, pesticides.
(6) Cigarette smoke — tar, nicotine, CO.
(7) Construction dust — PM.
Effects on human health:
(1) Respiratory problems: Asthma, bronchitis, COPD (from PM, SO₂, NOx, ozone).
(2) Lung cancer — PM2.5, PAHs, benzene.
(3) Cardiovascular diseases — PM2.5 enters bloodstream, causes inflammation.
(4) CO poisoning: Carboxyhemoglobin → reduced O₂ transport → headache, death.
(5) Eye irritation, conjunctivitis — smog, ozone.
(6) Skin problems — from smog, pollutants.
(7) Reduced life expectancy — long-term exposure.
(8) Neurological effects — lead, mercury.
(9) Reproductive problems — some pollutants affect fertility.
(A) Both true, R explains A. (B) Both true, R does NOT explain A. (C) A true, R false. (D) A false, R true.
All key facts at one place — perfect for quick revision.