Humans and populations

Definition and Nature of Pollution

Pollution is defined as the addition of a substance or agent to an environment through human activity, at a rate greater than it can be rendered harmless by the environment, which has an appreciable effect on organisms. This definition encompasses a wide range of human-induced environmental changes that negatively impact ecosystems and living beings.

The key aspects of this definition are:

1. Human activity as the source
2. Rate of introduction exceeding the environment's capacity to neutralize
3. Noticeable impact on organisms

Types and Sources of Pollutants

Organic and Inorganic Substances

Pollutants can be categorized into organic and inorganic substances:

1. Organic pollutants: These are carbon-based compounds, often derived from living organisms or synthetic processes. Examples include:
   • Pesticides (e.g., DDT)
   • Polychlorinated biphenyls (PCBs)
   • Petroleum products
2. Inorganic pollutants: These are typically mineral-based substances that do not contain carbon. Examples include:
   • Heavy metals (e.g., lead, mercury, cadmium)
   • Nitrates and phosphates from fertilizers
   • Sulfur dioxide and nitrogen oxides from industrial processes

Energy Pollutants

Pollution is not limited to chemical substances. Various forms of energy can also be pollutants:

1. Light pollution: Excessive or misdirected artificial light that affects natural light cycles.

1. Noise pollution: Unwanted or excessive sound that can harm human health and wildlife.

1. Thermal pollution: The release of heated water into natural water bodies, often from industrial cooling processes.

Biological Agents and Invasive Species

Biological pollution involves the introduction of organisms into ecosystems where they are not naturally present:

1. Pathogens: Disease-causing microorganisms introduced into water bodies or soil.
2. Invasive species: Non-native plants or animals that can outcompete native species and disrupt ecosystems.

Major Sources of Pollution

1. Combustion of fossil fuels:
   • Vehicle emissions
   • Power plant emissions
   • Industrial processes
2. Agricultural activities:
   • Pesticide and fertilizer runoff
   • Animal waste
3. Industrial processes:
   • Chemical manufacturing
   • Mining and mineral processing
   • Textile and paper production
4. Urban development:
   • Construction activities
   • Wastewater and sewage
   • Solid waste disposal

Characteristics of Pollutants

Point Source vs Non-Point Source

1. Point source pollution:
   • Originates from a single, identifiable source
   • Examples: Factory discharge pipes, oil spills from tankers
   • Easier to monitor and regulate
2. Non-point source pollution:
   • Comes from multiple diffuse sources
   • Examples: Agricultural runoff, urban stormwater
   • More challenging to control and manage

Persistent vs Biodegradable

1. Persistent pollutants:
   • Resist breakdown in the environment
   • Can accumulate in food chains (bioaccumulation)
   • Examples: PCBs, heavy metals
2. Biodegradable pollutants:
   • Can be broken down by natural processes
   • Less long-term environmental impact
   • Examples: Sewage, some types of plastics

Acute vs Chronic

1. Acute pollution:
   • Short-term, high-impact events
   • Often results in immediate, visible effects
   • Example: Chemical spills, severe air pollution episodes
2. Chronic pollution:
   • Long-term, continuous exposure to pollutants
   • Effects may not be immediately apparent
   • Example: Low-level exposure to air pollutants in urban areas

Primary vs Secondary Pollutants