Natural Disasters

Natural disasters are sudden, extreme events resulting from environmental factors that can cause injury and property damage. Common examples include:

• Droughts
• Windstorms
• Earthquakes
• Wildfires
• Floods
• Hurricanes
• Thunderstorms
• Volcanic eruptions

Impact of Human Activities on Natural Disasters

Human actions significantly influence the occurrence and severity of natural disasters, particularly floods, through:

• Deforestation: Removing trees and vegetation leads to bare land, increasing erosion and making water flow faster across hard surfaces like concrete.
• Urban Development: Expansion of urban areas disrupts natural waterways, altering the landscape and increasing flood risk.
• Destruction of Wetlands: Wetlands play a crucial role in absorbing excess water. Their destruction can lead to severe flooding during heavy rainfall.
• Agriculture: Large-scale agricultural practices can deplete topsoil and weaken vegetation, reducing land’s ability to absorb water and protect against flooding.

Effects of Natural and Human Activities on the Atmosphere

The combined effects of natural disasters and human activities can lead to:

• Destruction of buildings
• Loss of life (humans and animals)
• Altered landscapes
• Damage to vegetation
• Global warming due to harmful gas emissions

Greenhouse Gases

Greenhouse gases are atmospheric components that trap heat, contributing to global temperature rise. Key greenhouse gases include:

• Carbon Dioxide (CO2)
• Methane (CH4)
• Nitrogen Oxides (NO, NO2)
• Sulphur Dioxide (SO2)

Sources of Greenhouse Gases

• Carbon Dioxide (CO2):
  • Produced through combustion, respiration, fermentation, and decomposition.
• Methane (CH4):
  • Found in natural gas, wetlands, oceans, and produced by termites.
• Nitrogen Oxides (NO, NO2):
  • Generated from natural processes (like lightning) and the combustion of fossil fuels.
• Sulphur Dioxide (SO2):
  • Emitted from fossil fuel combustion in power plants and metal ore extraction.

Global Warming

Global warming refers to the ongoing increase in Earth’s average temperature due to the accumulation of greenhouse gases.

Mechanism of Greenhouse Effect

1. The sun emits energy as light and ultraviolet (UV) rays.
2. This energy warms the Earth, which then reflects some as heat.
3. Some heat escapes into space, while greenhouse gases in the atmosphere absorb and re-radiate some of this heat, warming the air and the Earth.

Key Contributors to Global Warming

Carbon dioxide and methane are the primary greenhouse gases responsible for global warming, with their levels on the rise:

• Carbon Dioxide: Increased fossil fuel combustion contributes to higher CO2 levels.
• Methane: Rising animal farming, rice cultivation, and landfill sites increase methane emissions.

Mitigating Global Warming

To address the effects of global warming, several strategies can be implemented:

• Renewable Energy: Utilize solar, wind, and hydroelectric power to reduce reliance on fossil fuels.
• Catalytic Converters: Install in automobiles to reduce exhaust emissions before they enter the atmosphere.
• Afforestation: Plant trees to absorb carbon dioxide and combat deforestation, enhancing carbon sequestration.

Air Quality Standards

International air quality standards, largely based on guidelines from the World Health Organization (WHO), aim to limit gas emissions and ensure cleaner air. In Malawi, the Malawi Bureau of Standards (MBS) has published specific guidelines on allowable emissions for various pollutants.

Ambient Air Quality Standards in Malawi

• Suspended Particulate Matter: 25 µg/m³ (1 day)
• Carbon Monoxide:
  • 9 ppm (8 hours)
  • 35 ppm (1 hour)
• Sulphur Dioxide:
  • 0.20 ppm (1 hour)
  • 0.08 ppm (1 day)
  • 0.02 ppm (1 year)
• Nitrogen Dioxide: 0.3 ppm (1 year)
• Ozone: 0.12 ppm (1 hour)
• Lead: 0.50 µg/m³ (1 year)
• Photochemical Oxidants:
  • 0.10 ppm (1 hour)
  • 0.08 ppm (4 hours)

Motor Vehicle Air Quality Standards in Malawi

• Hydrocarbons: 160 µg/m³ (3 hours), typical high concentration: 6 ppm
• Carbon Monoxide: 10 µg/m³ (8 hours), typical high concentration: 40 ppm
• Nitrogen Dioxide: 100 µg/m³ (1 year), typical high concentration: 0.1 ppm
• Oxidants: 160 µg/m³ (1 hour), typical high concentration: 0.6 ppm

The Ozone Layer

The ozone layer is a region in the Earth’s stratosphere, located approximately 20 to 30 km above the surface, that absorbs most of the sun’s harmful ultraviolet (UV) radiation.

Importance of the Ozone Layer

• Protection Against UV Rays: The ozone layer absorbs 93% to 99% of UV light, which can be harmful to living organisms.
• Health Risks from UV Exposure: Exposure can lead to:
  • Skin cancer
  • Damage to crops
  • Harm to aquatic life

Depletion of the Ozone Layer

Chlorofluorocarbons (CFCs) are the primary agents responsible for ozone layer depletion. Common sources of CFCs include coolants, foams, and aerosol products. When CFCs reach the atmosphere, chlorine atoms are released, which react with ozone (O₃) to form oxygen (O₂) and further deplete the ozone layer.

Chemical Reactions Involved

1. Decomposition of Ozone:
   • O₃ → O₂ + [O]
   • O₃ + [O] → 2 O₂

This reaction diminishes the ozone layer’s ability to shield the Earth from UV radiation.

Problems Associated with Ozone Layer Depletion

The depletion of the ozone layer leads to various health and environmental issues:

• Health Effects:
  • Increased risk of skin cancer
  • Cataract formation
  • Weakened immune system
  • Premature skin aging
  • Respiratory issues (e.g., difficulty breathing, chest pain)
• Environmental Impact:
  • Decline in amphibian populations, affecting their life cycles
  • Disruption of food chains and biogeochemical cycles
  • Alteration of physiological processes in plants

Addressing ozone layer depletion is critical to protecting human health and preserving ecosystems.

Depletion of the Ozone Layer

The primary agents responsible for the depletion of the ozone layer are chlorofluorocarbons (CFCs). These compounds are commonly found in products such as coolants, foams, and aerosol sprays.

How CFCs Cause Ozone Depletion

1. Release of CFCs: When these products are used, CFCs are released into the atmosphere.
2. Chlorine Atom Release: Once in the atmosphere, CFCs undergo chemical reactions triggered by ultraviolet (UV) radiation. This process releases chlorine atoms.
3. Chemical Reactions:
   • The released chlorine reacts with ozone (O₃) in the stratosphere.
   • The following chemical reactions occur:
     • Decomposition of Ozone:
       • O3→O2+[O]
       • O3+[O]→2O2

Impact on Ozone Layer

These reactions result in the conversion of ozone into oxygen (O₂), which diminishes the ozone layer’s capacity to shield the Earth from harmful UV radiation. As a result, increased UV exposure can lead to serious health risks and environmental damage.