Point source
A pollution source identifiable as coming from a single, specific location, such as a discharge pipe.
Water PollutionNonpoint source
A diffuse pollution source with no single identifiable origin, such as agricultural runoff.
Water PollutionEutrophication
Excess nutrients triggering algal blooms; decomposition of the algae depletes dissolved oxygen.
Water PollutionDead zone
An area of water with severely depleted oxygen where most aquatic life cannot survive, often from eutrophication.
Water PollutionThermal pollution
An artificial increase in water temperature, often from power plant cooling systems, reducing dissolved oxygen.
Water PollutionPersistent organic pollutants (POPs)
Toxic chemicals like DDT and PCBs that resist environmental breakdown and persist for years.
ToxicologyBioaccumulation
The buildup of a toxin within an individual organism over its lifetime.
ToxicologyBiomagnification
The increasing concentration of a toxin at each successive trophic level in a food chain.
ToxicologyLD50
The dose of a substance that causes death in 50% of a test population, used to compare relative toxicity.
ToxicologyEndocrine disruptor
A chemical that interferes with hormone system function, sometimes at very low concentrations.
ToxicologyDose-response curve
A graph showing how the effect on an organism changes as the dose of a chemical increases, used to compare toxicity and identify thresholds.
ToxicologyThreshold dose
The lowest dose of a substance at which a measurable effect first appears; below it, no response is observed.
ToxicologyAcute vs. chronic exposure
Acute exposure is a single, short, high-dose event; chronic exposure is repeated or long-term exposure to lower doses.
ToxicologyWetland
Land saturated with water that filters pollutants, stores floodwater, and provides critical habitat and nursery grounds.
Water PollutionMangrove
Salt-tolerant coastal trees whose roots stabilize shorelines, buffer storm surge, and shelter juvenile fish — threatened by clearing and development.
Water PollutionSanitary landfill
An engineered solid waste disposal site, lined to prevent leachate contamination and capped to control gas emissions.
Solid WasteLeachate
Contaminated liquid formed as water percolates through landfill waste.
Solid WasteIncineration
Burning solid waste to reduce volume, sometimes generating energy but releasing air pollutants and toxic ash.
Solid WasteWaste management hierarchy
A prioritized strategy: reduce, then reuse, then recycle/compost, with disposal as the last resort.
Solid WastePrimary treatment
The first sewage treatment stage, physically removing large solids through screening and settling.
SewageSecondary treatment
The treatment stage using microorganisms to biologically break down dissolved organic matter.
SewageTertiary treatment
The most advanced treatment stage, removing remaining nutrients and pathogens.
SewagePathogen
A disease-causing organism spread through contaminated water and poor sanitation.
Disease