Impact of water pollution - Environmental Management (0680) - Cambridge IGCSE

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🌊 Environmental Management (0680): Impact of Water Pollution 🌊

Welcome, IGCSE Environmental Managers!

Water is the essence of life, but human activities often contaminate this vital resource. In this chapter, we will explore the serious consequences—for both people and the planet—that occur when our rivers, lakes, and groundwaters become polluted. Understanding these impacts is crucial for effective water management.

Don't worry if some terms sound complicated! We will break down processes like *bioaccumulation* and *eutrophication* step-by-step. Let's dive in!

Part 1: Impact of Water Pollution on People and Health

The most immediate and critical impact of fresh water pollution on humans is the risk of spreading disease. When water is contaminated, especially with untreated sewage, it becomes unsafe to drink. This is a major global issue.

1.1 The Risk of Infectious Bacterial Diseases

When domestic waste, particularly sewage (fecal matter), enters drinking water sources, it carries harmful microorganisms (pathogens).

Typhoid: A bacterial infection that causes high fever and potentially severe complications.
Cholera: A serious bacterial disease causing severe diarrhea and dehydration, often leading to death if not treated quickly.

Imagine drinking water straight from a river that flows past a village with no sewage treatment—the water is full of germs! These diseases spread rapidly in areas where potable water (safe drinking water) is scarce.

1.2 Global Inequalities in Water Treatment

The ability to treat sewage and provide safe drinking water is unequal across the world:

In Water-Rich / Economically Developed Regions (MEDCs): Comprehensive sewage treatment plants and water purification systems are common. This significantly reduces the risk of waterborne diseases like cholera.
In Water-Poor / Less Economically Developed Regions (LEDCs): Treatment facilities are often lacking or poorly maintained, especially in rural areas. This means raw sewage often goes directly into rivers or groundwater, leading to high rates of waterborne disease.

Quick Review: Unsafe water leads to disease. The lack of proper sanitation systems, particularly in poorer regions, is the main driver of deadly epidemics like cholera.

Part 2: Impact of Water Pollution on the Environment (Ecosystems)

2.1 Accumulation of Toxic Substances

Industrial processes (like manufacturing, mining, and power generation) often discharge toxic waste into water bodies (lakes and rivers). These toxic substances include:

Heavy Metals: Such as mercury, lead, and cadmium.
Pesticides and PCBs: Man-made chemicals used in agriculture or industrial cooling.

These toxins are often non-biodegradable, meaning they do not naturally break down. They settle in the sediment or are taken up by aquatic organisms.

2.2 Bioaccumulation and Food Chains

When toxic substances enter an ecosystem, they pose a severe threat through the food chain.

Bioaccumulation: This is when a toxic substance builds up inside a single organism over its lifetime because the organism takes in the toxin faster than it can excrete it.
Biomagnification (Accumulation in Food Chains): This is the process where the concentration of the toxin increases at each successive trophic level in a food chain.

Step-by-Step Biomagnification:

Small plankton absorb trace amounts of mercury from the water.
Small fish eat many plankton, accumulating the mercury from all of them.
Large fish eat many small fish, accumulating even higher, more dangerous concentrations.
Humans (or top predators like birds of prey) eat the large fish, receiving a potentially toxic dose.

Did You Know? This is why governments sometimes issue warnings about eating large, long-lived predatory fish (like tuna or swordfish) due to high mercury levels.

2.3 The Effect of Acid Rain

Acid rain results from atmospheric pollution (sulfur dioxide and nitrogen oxides from factories and vehicles). This acid precipitation falls into rivers and lakes, lowering the pH (making the water more acidic).

Impact on Organisms: Many aquatic organisms, particularly delicate species like shrimp and insect larvae, cannot survive in acidic conditions.
Reproduction Failure: Fish are especially sensitive during their early life stages. Acidic water can prevent fish eggs and larvae from developing and hatching, leading to reduced fish populations and potentially total ecosystem collapse.
Example: In some highly industrial areas, lakes have become so acidic that they are virtually dead.

Key Takeaway: Toxic industrial waste gets concentrated in animals higher up the food chain, while acid rain destroys the sensitive reproductive cycles of lower aquatic life.

Part 3: Nutrient Enrichment and Eutrophication (The Oxygen Killer)

Nutrient pollution is perhaps the most common and widespread impact of pollution on freshwater ecosystems.

Nutrient Sources:

Agricultural practices: Runoff of excess fertilisers (rich in nitrates and phosphates).
Domestic waste: Sewage and detergents containing phosphates.

3.1 The Process of Eutrophication

Eutrophication is the enrichment of water bodies by nutrients, leading to excessive growth of plants and algae, and ultimately, a lack of oxygen.

Don't worry if this seems tricky at first. Let's follow the steps—it's like a chain reaction!

Step 1: Nutrient Overload (The Feast)

Excessive nitrates (NO₃^-) and phosphates (PO₄^3-) wash into the lake or river. These nutrients act like a massive dose of fertiliser for tiny aquatic plants (algae and phytoplankton).

Step 2: Algal Bloom (The Green Blanket)

The algae reproduce uncontrollably, forming a dense, thick layer on the surface called an algal bloom. This blocks sunlight from reaching plants living deeper down, killing them.

Step 3: Death and Decomposition (The Clean-up Crew Arrives)

The algae die (usually because they run out of nutrients or sunlight). They sink to the bottom. Large numbers of decomposer bacteria arrive to break down this dead organic matter.

Step 4: Oxygen Depletion (The Oxygen Crisis)

The decomposers use up vast amounts of Dissolved Oxygen (DO) during respiration as they break down the huge supply of dead material. This high oxygen demand is sometimes measured as BOD (Biological Oxygen Demand).

Step 5: Ecosystem Collapse (The Fish Die-Off)

The DO levels in the water drop dramatically. Fish and other aerobic (oxygen-requiring) organisms cannot breathe and they suffocate, leading to mass death (a 'fish kill'). The water body becomes an unpleasant, smelly, deoxygenated swamp.

Memory Aid for Eutrophication: Think of it as a party gone wrong! Too much food (nutrients) leads to too many guests (algae), a huge clean-up job (bacteria), and then everyone suffocates because the oxygen runs out.

Summary of Impacts:

Human Impacts:

Infectious diseases (Typhoid, Cholera).
Toxins in food (Biomagnification in fish).

Environmental Impacts:

Acidification of water bodies (kills fish and larvae).
Toxicity from industrial chemicals (kills organisms).
Eutrophication (depletes oxygen, kills fish, damages habitat).