Unit 4: Major environmental issues
Table of Contents
Global Atmospheric Issues
Greenhouse Effect and Global Warming
- Greenhouse Effect: A natural process that warms the Earth's surface. Greenhouse gases (GHGs) like CO₂, Methane (CH₄), and Water Vapour (H₂O) trap some of the outgoing infrared radiation (heat) from Earth, acting like a blanket.
- Global Warming: The enhancement of the natural greenhouse effect due to human activities, primarily the burning of fossil fuels, which releases excess CO₂ and other GHGs into the atmosphere, causing the planet's average temperature to rise.
- Climate Change: The long-term change in average weather patterns that defines Earth's local, regional, and global climates. Global warming is a key aspect of climate change, leading to sea-level rise, melting glaciers, and more extreme weather events.
Ozone Layer Depletion
- What it is: The thinning of the protective stratospheric ozone layer, which filters harmful UV-B radiation from the sun.
- Cause: Man-made chemicals, especially Chlorofluorocarbons (CFCs), which release chlorine radicals that catalytically destroy ozone.
- Effect: Increased UV-B radiation reaches Earth, causing skin cancer, cataracts, and damage to plants and plankton.
Acid Rain
- What it is: Rain, snow, or fog that is unusually acidic (pH < 5.6).
- Cause: Sulfur Dioxide (SO₂) from burning coal and Nitrogen Oxides (NOx) from vehicle exhaust react in the atmosphere to form Sulfuric Acid (H₂SO₄) and Nitric Acid (HNO₃).
- Effect: Makes lakes acidic (killing fish), damages forests, and corrodes buildings and statues.
Construction of Dams and Associated Environmental Issues
Large dams are built for hydroelectric power, irrigation, and flood control, but they have significant environmental and social impacts.
Environmental Issues
- Upstream: Submergence of large areas of forests and agricultural land, loss of biodiversity.
- Downstream: Reduced water flow, loss of nutrient-rich silt, and damage to deltas and fisheries.
- General: Fragmentation of river ecosystems, blocking fish migration routes, and potential for reservoir-induced seismicity (earthquakes).
Social Issues
- Large-scale displacement of people (often tribal and poor communities).
- Problems with resettlement and rehabilitation.
Case Studies of Environmental Disasters
These are critical examples of the consequences of pollution and industrial accidents.
| Disaster | What Happened | Pollutant / Cause | Key Consequence |
|---|---|---|---|
| Bhopal Gas Tragedy (India, 1984) | A gas leak at the Union Carbide pesticide plant. | Methyl Isocyanate (MIC) gas. | Thousands died instantly; many more suffered long-term health effects (blindness, respiratory failure). World's worst industrial disaster. |
| Minamata Disaster (Japan, 1950s) | A chemical factory discharged wastewater into Minamata Bay. | Methylmercury. | The mercury bio-magnified in fish. People who ate the fish suffered severe neurological damage, paralysis, and birth defects (known as Minamata disease). |
| Chernobyl Disaster (Ukraine, 1986) | A flawed reactor design and human error caused a catastrophic explosion and fire at a nuclear power plant. | Radioactive fallout (e.g., Caesium-137, Iodine-131). | Massive release of radiation across Europe, acute radiation sickness, long-term increase in thyroid cancer, and a large "exclusion zone." |
| Fukushima Nuclear Accidents (Japan, 2011) | A major earthquake and tsunami disabled the cooling systems of a nuclear power plant, leading to meltdowns. | Radioactive fallout. | Widespread radiation contamination, evacuation of over 100,000 people, and long-term contamination of the ocean. |
| Kalpakkam Disaster (India) | (Note: This likely refers to various safety incidents or concerns at the Kalpakkam nuclear facility, rather than a single large-scale disaster on par with Chernobyl or Fukushima). | Radioactive materials. | Concerns about worker safety, environmental contamination, and risks (e.g., from the 2004 tsunami). |