13.1 Air & Atmosphere
🌍 The Atmosphere
- Envelope of gases surrounding Earth
- 78% Nitrogen, 21% Oxygen
- Traces: CO₂, water vapor, noble gases
- Regulates temperature and weather
- Protects from solar radiation
📊 Atmospheric Layers
💨 Other Environmental Components
- Hydrosphere: All water bodies
- Lithosphere: Earth’s solid outer layer
- Biosphere: All living organisms
- All interconnected through natural processes
13.1.2 Air Pollutants
☣️ Types of Pollutants
Directly emitted
Formed in atmosphere
📋 Major Air Pollutants
| Pollutant | Formula | Major Sources | Effects |
|---|---|---|---|
| Particulate Matter | PM2.5/PM10 | Combustion, dust | Respiratory issues |
| Nitrogen Oxides | NOₓ | Vehicles, industry | Smog, acid rain |
| Sulfur Dioxide | SO₂ | Coal burning | Acid rain |
| Carbon Monoxide | CO | Incomplete combustion | Cardiovascular |
| Volatile Organics | VOCs | Vehicles, solvents | Ozone formation |
| Ozone (Ground) | O₃ | NOₓ + VOCs + sunlight | Lung damage |
| Heavy Metals | Pb, Hg, Cd | Industry | Health, environment |
13.2 SMOG
🌫️ What is Smog?
- Air pollution = Fog + Smoke
- Hazy, yellowish appearance
- Reduces visibility dangerously
- Forms from pollutants + sunlight
🔍 Types of Smog
• Urban areas
• Vehicles emissions
• NOₓ + VOCs + sunlight
• Contains ozone
• “Brown smog”
• Coal burning areas
• Particulate matter + SO₂
• “Black smog”
• London-type smog
• Grey color
⚗️ Formation Reactions
Photochemical Smog Formation
NO₂ + sunlight → NO + O
O + O₂ → O₃ (ozone)
NO + O₃ → NO₂ + O₂
NO₂ + VOCs → PAN (peroxyacetyl nitrate)
⚠️ Hazardous Effects
- Respiratory problems (asthma, bronchitis)
- Cardiovascular issues
- Eye irritation
- Reduced visibility → accidents
- Crop damage
- Global warming contribution
13.3 ACID RAIN
🌧️ What is Acid Rain?
- Rainfall with pH < 5.6
- Normal rain pH ≈ 5.6 (slightly acidic from CO₂)
- Caused by SO₂ and NOₓ emissions
- Formation in atmosphere:
Acid Formation Reactions
Sulfuric Acid: 2SO₂ + O₂ + 2H₂O → 2H₂SO₄
Nitric Acid: NO₂ + H₂O → HNO₃
🔥 Sources
- Burning fossil fuels (coal, oil)
- Industrial processes
- Vehicle emissions
- Power plants
💔 Impacts
Also: Human health effects, biodiversity loss, economic costs
13.7 Greenhouse Effect & Global Warming
🌡️ Greenhouse Effect
- Natural phenomenon
- Traps heat in atmosphere
- Essential for life (Earth’s average temp: 15°C)
- Enhanced by human activities
🔥 Greenhouse Gases
| Gas | Formula | Sources | Global Warming Potential |
|---|---|---|---|
| Carbon Dioxide | CO₂ | Fossil fuels, deforestation | 1 (reference) |
| Methane | CH₄ | Agriculture, waste | 25× CO₂ |
| Nitrous Oxide | N₂O | Fertilizers, industry | 298× CO₂ |
| CFCs | CFCs | Refrigerants, aerosols | 1000s× CO₂ |
📈 Global Warming Causes
🌊 Consequences
- Rising temperatures
- Melting ice → sea level rise
- Extreme weather events
- Ecosystem disruption
- Human health impacts
- Food and water shortages
13.4 Air Quality Parameters
📊 Air Quality Index (AQI)
- Standardized measure of air quality
- Based on multiple pollutants
- Categories: Good, Moderate, Unhealthy, etc.
- Calculated from: PM2.5, PM10, O₃, CO, SO₂, NO₂
🔬 Monitoring Methods
• Beta attenuation
• Gravimetric
• Optical counters
• Electrochemical sensors
• Infrared spectroscopy
• Gas chromatography
• Satellite data
• Large area coverage
• Modern method
• Hospital data analysis
• Public health impact
📋 National Standards (NAAQS 2009)
| Pollutant | Averaging Time | Standard (μg/m³) |
|---|---|---|
| PM2.5 | Annual/24-hour | 40/60 |
| PM10 | Annual/24-hour | 60/100 |
| Ozone | 8-hour | 100 |
| NO₂ | Annual/24-hour | 40/80 |
| SO₂ | Annual/24-hour | 50/80 |
| CO | 8-hour | 2 mg/m³ |
13.5 Laws & Control Measures
⚖️ Major Regulations
- Clean Air Act (USA): Comprehensive air quality law
- EU Air Quality Directive: European standards
- NAAQS: National Ambient Air Quality Standards
- Emissions Standards: Industry and vehicles
🛡️ Control Strategies
🌱 Specific Measures
- Renewable energy transition
- Electric vehicles
- Eco-friendly building designs
- Tree plantation
- Proper waste disposal
- Industrial best practices
- Emission trading schemes
- Vehicle testing programs
Exercise Questions – Complete Solutions
Multiple Choice Questions:
1. What is a primary source of air pollution?
Answer: (d) All of the above
Explanation: Air pollution comes from both natural (volcanic eruptions, forest fires) and anthropogenic sources (industrial emissions). All listed options are significant sources of air pollutants.
2. Which gas is primarily responsible for the greenhouse effect?
Answer: (b) Carbon dioxide (CO₂)
Explanation: While multiple gases contribute, CO₂ is the most significant anthropogenic greenhouse gas due to its abundance and long atmospheric lifetime.
3. Which of the following is NOT a greenhouse gas?
Answer: (c) Sulfur dioxide (SO₂)
Explanation: SO₂ causes acid rain but has negligible greenhouse effect. Methane, nitrous oxide, and water vapor are all greenhouse gases.
4. What is the main component of smog that poses health risks to humans?
Answer: (d) Nitrogen dioxide (NO₂)
Explanation: NO₂ is a key component of photochemical smog and causes respiratory problems. While ozone is also harmful, NO₂ is particularly damaging to lungs.
5. Acid rain is primarily caused by the emission of:
Answer: (c) Sulfur dioxide (SO₂)
Explanation: SO₂ reacts with water to form sulfuric acid, the main component of acid rain. NOₓ also contributes but SO₂ is the primary cause.
Short Answer Questions:
2. What are main sources of air pollution?
Answer: Natural and anthropogenic sources including:
- Natural: Volcanic eruptions, forest fires, dust storms, pollen
- Anthropogenic:
- Vehicles (cars, trucks, airplanes)
- Industrial processes (manufacturing, power plants)
- Agricultural activities (fertilizers, livestock)
- Residential (heating, cooking)
- Waste burning and landfills
3. Describe photochemical smog, its ingredients and health effects.
Answer: Photochemical smog is brownish haze formed in urban areas.
Ingredients: NOₓ + VOCs + Sunlight → Ozone (O₃) + PAN + other oxidants
Formation: Sunlight triggers reactions between vehicle emissions
Health Effects:
- Respiratory problems (asthma, bronchitis)
- Eye irritation and watering
- Reduced lung function
- Cardiovascular issues
- Increased mortality in vulnerable groups
4. Write down the reactions which are involved in the formation of acid rain.
Answer: Main reactions:
Sulfuric Acid Formation:
2SO₂ + O₂ → 2SO₃
SO₃ + H₂O → H₂SO₄
H₂SO₄ + H₂O → H₃O⁺ + HSO₄⁻
Nitric Acid Formation:
2NO₂ + H₂O → HNO₃ + HNO₂
HNO₃ + H₂O → H₃O⁺ + NO₃⁻
5. Describe the phenomenon of greenhouse effect.
Answer: Natural process where greenhouse gases trap heat.
Process:
- Sun emits shortwave radiation
- Earth absorbs and re-emits as longwave (IR) radiation
- Greenhouse gases (CO₂, CH₄, etc.) absorb IR radiation
- Gases re-radiate heat in all directions
- Some heat returns to Earth’s surface
Importance: Maintains Earth’s temperature at habitable level (15°C average)
Enhanced Effect: Human activities increase greenhouse gases → more heat trapped → global warming
8. Suggest some measures to reduce air pollution.
Answer: Multiple strategies at different levels:
• Use public transport
• Conserve energy
• Reduce, reuse, recycle
• Plant trees
• Avoid burning waste
• Carpooling programs
• Community gardens
• Awareness campaigns
• Waste management
• Green spaces
• Clean technologies
• Pollution control devices
• Renewable energy
• Waste treatment
• Sustainable practices
• Strict regulations
• Emission standards
• Renewable energy policies
• Environmental monitoring
• International agreements
10. Enlist some problems caused by global warming.
Answer: Global warming causes multiple interconnected problems:
- Environmental:
- Melting glaciers and ice caps
- Rising sea levels
- Ocean acidification
- Loss of biodiversity
- Coral bleaching
- Weather & Climate:
- More frequent heatwaves
- Intense storms and hurricanes
- Changing rainfall patterns
- Prolonged droughts
- Increased wildfires
- Human Impacts:
- Food and water insecurity
- Spread of diseases
- Displacement of populations
- Economic losses
- Health problems from heat
Project Suggestions:
1. Create posters to highlight the hazardous effects of environmental pollution.
Answer: Poster creation ideas:
(e.g., smog, acid rain)
appealing poster
Content ideas:
- Before/after photos of affected areas
- Statistics on health impacts
- Simple chemical reactions
- Prevention tips
- Local relevance (city/region specific)
Display: School notice boards, community centers, social media
2. Using instruments measure the particulate matter in industrial and residential areas.
Answer: Scientific investigation project:
Hypothesis: Industrial areas have higher particulate matter than residential areas.
Materials: PM2.5/PM10 monitor, notebook, map of city
Method:
- Select multiple sites in both area types
- Measure at same time of day
- Record weather conditions
- Take multiple readings
- Calculate averages
Data Analysis:
- Compare PM levels
- Identify patterns
- Relate to sources (factories, traffic)
- Compare with safety standards
Presentation: Charts, graphs, written report with conclusions