Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

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Performance objectives

• Explain the causes and consequences of pollution (air, water, soil).
• Describe the impact of deforestation and alien plant species.
• Analyse the causes and consequences of loss of biodiversity.
• Discuss sustainable resource management strategies.
• Apply knowledge to analyse South African environmental case studies.

Lesson summary

This week, we begin our exploration of one of the most critical topics in Life Sciences: the impact of human activities on the environment. This is not just an abstract, academic topic; it directly affects our lives in South Africa. From the air we breathe in Gauteng to the water scarcity faced in the Western Cape, and the biodiversity threatened across our country, understanding our environmental impact is crucial for a sustainable future. As future leaders, thinkers, and citizens, it's vital you understand the complex interplay between human actions and the environment to make informed decisions and contribute to positive change.

Lesson notes

2. 1.

Pollution: Air, Water, and Soil Air Pollution: Air pollution arises from the release of harmful substances into the atmosphere. In South Africa, major sources include: Industrial Emissions: Power plants (especially coal-fired ones like those operated by Eskom), factories, and mining operations release pollutants such as sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM), and heavy metals. These contribute to acid rain, respiratory problems, and smog.

Vehicle Emissions: Cars, trucks, and buses emit carbon monoxide (CO), NOx, and hydrocarbons, which contribute to greenhouse gases and respiratory issues, especially in urban areas like Johannesburg and Cape Town. The reliance on older vehicles in some areas exacerbates this.

Burning of Fossil Fuels: Domestic burning of coal and wood, particularly in informal settlements during winter, leads to high levels of PM2.5, posing serious health risks.

Mining Activities: Dust from mining operations contaminates the air with heavy metals like lead and arsenic.

Consequences: Respiratory Illnesses: Asthma, bronchitis, and lung cancer.

Acid Rain: Damages forests, aquatic ecosystems, and infrastructure.

Climate Change: Contributes to global warming and changing weather patterns.

Reduced Visibility: Smog affects tourism and transportation.

Example: Consider a coal-fired power plant in Mpumalanga. The plant releases SO2 into the air. SO2 reacts with water vapor in the atmosphere to form sulfuric acid (H2SO4), a component of acid rain. This acid rain damages nearby forests and contaminates rivers, impacting biodiversity and water quality.

Water Pollution: Water pollution occurs when harmful substances contaminate water bodies.

Key sources in South Africa include: Industrial Effluent: Factories release untreated or poorly treated wastewater containing toxic chemicals, heavy metals, and organic pollutants.

Agricultural Runoff: Fertilizers, pesticides, and herbicides from farms contaminate rivers and groundwater. Eutrophication (excessive nutrient enrichment) can occur, leading to algal blooms and oxygen depletion.

Sewage: Untreated or poorly treated sewage releases pathogens and organic matter into water bodies, posing health risks and disrupting aquatic ecosystems.

Mining Activities: Acid mine drainage (AMD), formed when water reacts with sulfide minerals in mine tailings, contaminates water with sulfuric acid and heavy metals. This is a severe problem in Gauteng and other mining regions.

Informal Settlements: Lack of proper sanitation leads to the direct discharge of sewage into rivers and streams.

Consequences: Waterborne Diseases: Cholera, typhoid, and diarrhea.

Eutrophication: Algal blooms, oxygen depletion, and fish kills.

Contamination of Drinking Water: Poses health risks to humans and animals.

Damage to Aquatic Ecosystems: Loss of biodiversity and disruption of food webs.

Example: Imagine a farm using excessive amounts of fertilizer. Rain washes the fertilizer into a nearby river. The fertilizer contains nitrates and phosphates, which act as nutrients for algae. The algae grow rapidly, forming a dense algal bloom. When the algae die, bacteria decompose them, consuming oxygen in the water. This oxygen depletion kills fish and other aquatic organisms.

Soil Pollution: Soil pollution results from the accumulation of harmful substances in the soil.

Main sources in South Africa include: Industrial Waste: Improper disposal of industrial waste contaminates soil with heavy metals, chemicals, and radioactive materials.

Mining Activities: Mine tailings and waste rock contaminate soil with heavy metals and acids.

Agricultural Practices: Excessive use of pesticides, herbicides, and fertilizers pollutes soil.

Sewage Sludge: Application of sewage sludge to agricultural land can introduce heavy metals and pathogens into the soil.

Waste Disposal: Improperly managed landfills contaminate soil with leachate (contaminated liquid).

Consequences: Contamination of Food Crops: Heavy metals and other pollutants can be taken up by plants, posing health risks to humans and animals.

Reduced Soil Fertility: Pollutants can inhibit plant growth and reduce agricultural productivity.

Groundwater Contamination: Pollutants can leach into groundwater, contaminating drinking water sources.

Health Risks: Exposure to contaminated soil can cause skin irritation, respiratory problems, and other health effects.

Example: A gold mine in Gauteng leaves behind large piles of mine tailings. Rainwater percolates through the tailings, dissolving heavy metals like arsenic and lead. The contaminated water seeps into the soil, poisoning the land and making it unsuitable for agriculture. The heavy metals can also be absorbed by plants grown on the contaminated soil, posing health risks to people who consume them. 2.

2. Deforestation and Alien Plant Species Deforestation: Deforestation is the clearing of forests for other land uses, such as agriculture, urban development, and mining.