Aquatic and Terrestrial Pollution

Notes

Sources of pollution

• Point source: a single identifiable source, like a factory pipe or sewage plant.
• Nonpoint source: spread out and hard to trace, like farm runoff or urban stormwater. Harder to regulate.

Water pollutants

• Nutrients (nitrates and phosphates from fertilizer and sewage) cause eutrophication: algal blooms, then decomposition uses up oxygen, creating hypoxic dead zones (like in the Gulf of Mexico).
• Thermal pollution: warm water from power plants holds less dissolved oxygen.
• Sediment makes water turbid, blocking light and smothering habitats.
• Oil spills coat animals and wetlands.
• Plastics break into microplastics that animals swallow.
• Coral reefs are harmed by warming (bleaching), sediment and pollution.
• Indicator species (like mayfly larvae) show water quality: many pollution-sensitive species mean clean water.

Toxins

• LD₅₀: the dose that kills 50% of a test population. A lower LD₅₀ means a more toxic substance.
• Bioaccumulation: a toxin builds up in one organism over its life. Biomagnification: the concentration increases at each higher trophic level. Examples: DDT (thinned eagle eggshells) and mercury in large fish like tuna.
• Persistent organic pollutants (POPs) don't break down easily and are fat-soluble.
• Endocrine disruptors interfere with hormones.

Solid waste and sewage

• Sanitary landfills use clay or plastic liners, leachate collection and methane capture. Problems: leachate, methane emissions, and limited space.
• Incineration reduces waste volume but produces air pollution and toxic ash.
• Reduce, reuse, recycle, and composting cut waste. E-waste contains heavy metals.
• Sewage treatment: primary (physical settling), secondary (bacteria break down organic matter), tertiary (removes nitrogen and phosphorus), then disinfection.
• Dose-response curves and pathogens (cholera, malaria) matter for human health; climate change can spread vector-borne diseases.