Unit 8: Aquatic and Terrestrial Pollution

Pollution

Any substance or form of energy introduced into the environment that causes harm to organisms, ecosystems, or human systems (e.g., drinking water supplies, agriculture).

Persistence

How long a pollutant lasts in the environment before it breaks down or is removed.

Mobility

How easily a pollutant moves through the environment (e.g., water-soluble pollutants spreading through groundwater and rivers).

Environmental transformation

Chemical, microbial, or sunlight-driven changes that convert a pollutant into a less harmful form or a more harmful form.

Methylmercury

A highly toxic, bioavailable form of mercury produced by microbes; strongly biomagnifies in food webs.

Point-source pollution

Pollution from a specific, identifiable source (e.g., a factory discharge pipe or wastewater treatment plant outfall), often easier to measure and regulate.

Nonpoint-source pollution

Pollution from many diffuse sources over a broad area (e.g., farm/lawn/street runoff), harder to regulate because there is no single outflow.

Watershed (drainage basin)

The land area that drains water to a common outlet (stream, river, lake, or ocean); pollutants released within it can be transported downhill into waterways.

Impermeable surface

A surface (e.g., pavement, rooftops) that blocks infiltration, increasing runoff and often increasing flooding and pollution transport.

Runoff

Water from rain or snowmelt that flows over land, picking up and transporting pollutants to storm drains and waterways.

Urban runoff

Runoff from cities (roads, parking lots, rooftops) that can carry oil, metals, sediment, trash, and fertilizers and is often a major driver of flooding and water pollution.

Groundwater recharge

The process of water infiltrating into the ground to replenish aquifers; reduced by impermeable surfaces, contributing to groundwater depletion.

Dissolved oxygen (DO)

The amount of oxygen gas dissolved in water; low DO can signal pollution and can lead to stress or death of aquatic organisms.

Temperature (water quality indicator)

A factor affecting water quality because warmer water holds less dissolved oxygen and can increase organisms’ metabolic stress and sensitivity to toxins/disease.

pH

A measure of acidity/basicity; many waters have highest biodiversity near pH 7, and lower pH can increase heavy-metal solubility and toxicity.

Turbidity

Cloudiness from suspended particles that scatter light; reduces light penetration, harms photosynthesis, and can damage fish gills.

Nutrients (nitrogen and phosphorus)

Essential elements at low levels, but in excess can drive algal blooms and major ecosystem changes, often leading to oxygen depletion.

Pathogens

Disease-causing organisms (often linked to fecal contamination) that can make people ill and contaminate aquatic food sources like shellfish.

Alkalinity

A measure of bicarbonate, carbonate, and hydroxide ions that buffer water against pH change (higher alkalinity = greater resistance to pH swings).

Coliform bacteria

Bacteria associated with intestines of warm-blooded animals; their presence suggests possible untreated sewage contamination (fecal coliform is a key subset).

Oxygen-demanding wastes

Organic materials (e.g., sewage, manure, food waste) that decomposers break down while consuming dissolved oxygen.

Biochemical oxygen demand (BOD)

An estimate of biodegradable organic pollution based on how much oxygen microbes require to decompose organic matter in a water sample; high BOD often leads to low DO.

Nitrate

A water-soluble nitrogen form commonly from fertilizers; can leach into groundwater or run off to surface waters, promoting algal blooms and DO decline.

Phosphate

A phosphorus form from fertilizers/household sources that often adheres to soil particles; erosion and sediment transport are major delivery pathways to water.

Sediment pollution

Excess soil in waterways from erosion (construction, agriculture, deforestation, streambanks) that increases turbidity, smothers eggs/benthic life, and carries attached pollutants.

Thermal pollution

Degradation of water quality by temperature change (often warmer discharge from power plants/industry), which lowers DO and can kill temperature-sensitive species.

Eutrophication

Nutrient enrichment (especially N and P) that increases plant/algal growth and can trigger downstream oxygen depletion.

Cultural eutrophication

Human-caused eutrophication from increased nutrient inputs (e.g., fertilizers, sewage, failing septic systems) leading to blooms and hypoxia.

Hypoxia

Low dissolved oxygen conditions that can cause fish/invertebrates to die or flee; often follows algal bloom die-offs and decomposition.

Dead zone

A (often seasonal) low-oxygen area—commonly in coastal waters—where many organisms cannot survive due to hypoxia from nutrient-driven decomposition.

Harmful algal bloom (HAB)

A rapid increase in algae or phytoplankton (sometimes toxin-producing) that raises turbidity and can contribute to oxygen depletion and ecosystem disruption.

Pesticide

A chemical used to kill/control pests (herbicides, insecticides, fungicides, rodenticides) that can drift, run off, persist, and harm non-target species.

Integrated pest management (IPM)

A pest-control approach that reduces reliance on broad chemical use by combining monitoring, prevention, biological controls, and targeted/limited pesticide application.

Persistent organic pollutants (POPs)

Long-lasting carbon-based chemicals resistant to breakdown that can travel long distances, bioaccumulate in tissues, and biomagnify through food chains.

Global distillation effect

The tendency for some POPs to evaporate in warm regions, travel through the atmosphere, and condense/accumulate in colder regions.

Bioaccumulation

An increase in pollutant concentration within a single organism over time because intake exceeds elimination.

Biomagnification

An increase in pollutant concentration at higher trophic levels in a food chain; top predators often have the highest concentrations.

Endocrine disruptors

Chemicals that interfere with hormone systems by mimicking hormones, blocking receptors, or altering hormone production, potentially causing developmental and reproductive effects at low doses.

Heavy metals

Naturally occurring elements (e.g., mercury, lead, cadmium, arsenic) that can be toxic at low concentrations and do not biodegrade into harmless components.

Acid mine drainage

Acidic runoff formed when exposed sulfide minerals react with oxygen and water during/after mining, increasing metal solubility and mobilizing dissolved metals into streams.

Tailings

Waste rock/material left after mining; runoff over tailings can carry sediments and associated pollutants (including metals) into waterways.

Combined sewer overflow (CSO)

A release of untreated or partially treated sewage mixed with stormwater when heavy rainfall exceeds the capacity of a combined sewer system.

Septic system

Onsite wastewater treatment using a tank (solids settle, oils float) and a drain field where soil and microbes reduce organic matter and pathogens; can contaminate groundwater if poorly sited/maintained.

Primary treatment

The physical stage of municipal sewage treatment using screens and settling to remove trash, grit, and some suspended solids (does not remove most dissolved nutrients).

Secondary treatment

The biological stage of municipal sewage treatment where microbes (often in aerated systems) break down dissolved and fine organic matter, removing much of BOD.

Tertiary (advanced) treatment

An additional treatment stage that targets remaining pollutants—especially nitrogen and phosphorus—using filtration, chemical precipitation (for P), and/or biological nutrient removal.

Clean Water Act (CWA)

U.S. law that regulates pollutant discharges into surface waters, especially through permitting of point-source pollution.

Safe Drinking Water Act (SDWA)

U.S. law focused on regulating contaminants in drinking water supplies (tap water safety).

RCRA (Resource Conservation and Recovery Act)

U.S. law that manages hazardous waste from “cradle to grave,” covering generation through transport, treatment, storage, and disposal.

CERCLA (Superfund)

U.S. law that funds and requires cleanup of contaminated sites and assigns liability for hazardous waste releases.