2.2H Pollutants and human activities Notes

1. Non-biodegradable pollutants are substances that cannot be broken down by natural biological processes.
2. Examples include polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), and mercury.
3. These pollutants persist in the environment for decades, becoming toxic hazards that accumulate in organisms and magnify through food chains.
4. These pollutants affect ecosystems through two main processes -bioaccumulation and biomagnification.

Bioaccumulation

1. Bioaccumulation occurs when an organism absorbs a pollutant faster than it can excrete it.
2. Pollutants enter organisms through:
   1. Direct absorption from water or soil.
   2. Ingestion of contaminated food or prey.
   3. Respiration (in the case of volatile pollutants).
3. Over time, this results in increased internal concentrations, especially in long-lived organisms.

Biomagnification

1. Biomagnification refers to the progressive increase in pollutant concentration at successive trophic levels of a food chain.
2. At each step, consumers ingest the accumulated pollutants from their prey. Since these pollutants are non-biodegradable and fat-soluble, they are retained and further concentrated in their tissues.
3. As a result, top predators exhibit the highest concentrations of toxic substances.

Environmental and Biological Consequences

1. Top predators (e.g., eagles, seals, humans) are most at risk.
2. Persistent pollutants can cause:
   1. Reduced reproductive success (e.g., eggshell thinning)
   2. Neurological and developmental damage
   3. Hormonal imbalances and carcinogenic effects
   4. Disruption of aquatic and terrestrial food webs

Microplastics and Non-biodegradable Pollutants

1. Microplastics are non-biodegradable and can persist in marine and terrestrial ecosystems for centuries.
2. When combined with other persistent organic pollutants (POPs), microplastics act as vectors, absorbing and transporting harmful chemicals through food chains.

How Microplastics Spread Pollutants

1. Absorption of Pollutants: Microplastics have large surface areas and hydrophobic properties, allowing them to attract and bind pollutants like PCBs, pesticides, and heavy metals.
2. Ingestion by Marine Life: Plankton, shellfish, and fish mistake microplastics for food, ingesting them directly.
3. Transfer Through the Food Chain: Polluted microplastics pass from prey to predator, increasing pollutant concentration through biomagnification.
4. Human Exposure: Humans ingest microplastics and associated pollutants through seafood, table salt, and drinking water.

Effects on Ecosystems and Human Health

1. Reduces reproductive success and growth in marine species.
2. Alters feeding behavior and digestive processes.
3. Pollutants attached to microplastics cause endocrine disruption and immune dysfunction.
4. Humans consuming contaminated seafood risk exposure to heavy metals and POPs.

Human Impacts on Energy and Matter Flows in Ecosystems

1. Human activities have dramatically altered the flow of energy and transfer of matter in ecosystems.
2. These impacts disrupt photosynthesis, nutrient cycling, and overall ecosystem productivity.

1. Burning Fossil Fuels

1. Releases CO₂, SO₂, and nitrogen oxides (NOₓ) into the atmosphere.
2. Increases greenhouse gas concentrations, contributing to global warming.
3. Alters the carbon cycle by adding stored carbon (from fossil fuels) into the atmosphere.
4. While increased CO₂ can enhance photosynthesis (CO₂ fertilization effect), overall impacts such as acid rain, temperature rise, and climate instability reduce net primary productivity (NPP).

2. Deforestation

1. Removes large carbon sinks, decreasing CO₂ absorption.
2. Reduces biomass and energy storage within ecosystems.
3. Disrupts water and nutrient cycles by increasing soil erosion and runoff.
4. Leads to loss of biodiversity and collapse of food webs.

3. Urbanization

1. Replaces natural vegetation with impervious surfaces (concrete, asphalt).
2. Decreases photosynthetic area and carbon sequestration capacity.
3. Creates urban heat islands, altering local microclimates and increasing energy demand.
4. Increases pollution runoff into rivers, affecting aquatic nutrient balances.

4. Agriculture

1. Intensive agriculture uses fertilizers, pesticides, and monocultures, altering nutrient cycles.
2. Fertilizer runoff increases nitrogen and phosphorus levels in water bodies → eutrophication and oxygen depletion.
3. Pesticides enter food webs, leading to bioaccumulation in non-target species.
4. Repeated tilling and irrigation degrade soil structure and reduce organic matter.

Global Implications

1. Reduced primary productivity due to habitat loss and pollution.
2. Altered nutrient cycles (carbon, nitrogen, phosphorus).
3. Climate change effects amplify existing ecosystem stresses.
4. Human health impacts from pollutant accumulation in food webs.