Unit 8 Beta

Aquatic and Terrestrial Pollution: the one-page sheet

8.1 Sources of Pollution

Point sources release pollution from one identifiable place, such as a pipe or smokestack, so they can be measured, permitted and treated. Nonpoint sources, such as runoff from farms, lawns and streets, come from many diffuse places. Laws have cut point sources sharply, so nonpoint pollution is now the largest share, and it is reduced by changing how land is used.

A point source comes from one identifiable place: a discharge pipe, a smokestack, a leaking tank or an oil tanker.
A nonpoint source comes from many diffuse places: runoff from farms, lawns and streets, eroded sediment, and car exhaust across a city.
Point sources are easier to measure, permit and treat, so laws such as the Clean Water Act have cut them a lot. Nonpoint sources now cause most water pollution.
Nonpoint fixes work on the land: buffer strips, rain gardens, permeable pavement, careful fertilizer use and erosion control.

it is a point source that can be found, measured and given a permit runoff picks up fertilizer, sediment, oil, metals and pet waste from many places it is nonpoint pollution, with no single place to measure or treat nonpoint sources are now the largest share of water pollution and need land-use solutions

point source: Pollution that enters the environment from one identifiable place, such as a factory discharge pipe, a sewage outfall, a smokestack or a leaking storage tank.
nonpoint source: Pollution that comes from many diffuse places rather than one outlet, such as runoff from farm fields, lawns and city streets, or exhaust from all the cars in a region.

8.2 Human Impacts on Ecosystems

Pollution changes ecosystems by pushing conditions outside species' tolerance ranges. Indicator species such as mayfly larvae reveal water quality. Heat stress bleaches corals by making them expel their algae; sediment smothers reefs; oil spills coat and poison wildlife; and plastics entangle animals and break into microplastics that enter food webs.

Species differ in their range of tolerance. Indicator species such as mayfly, stonefly and caddisfly larvae disappear when water quality falls; midges and worms tolerate pollution.
Coral bleaching: heat stress (and pollution) makes corals expel their algae, so they turn white and may starve. Sediment blocks light and smothers reefs.
Oil spills coat feathers and fur, poison animals and smother shorelines. Cleanup uses booms, skimmers and, with care, dispersants.
Ocean plastics entangle animals and are eaten; they break into microplastics that enter food webs and carry toxic chemicals.

conditions move outside the tolerance range of sensitive species the community changes, which indicator species reveal corals bleach, starve and may die, and reef species lose habitat animals lose insulation, are poisoned, or starve with full stomachs

indicator species: A species whose presence, absence or health reveals the condition of its environment. Mayfly and stonefly larvae, for example, need clean, oxygen-rich water.
coral bleaching: The whitening of corals when stress, usually warm water, makes them expel the algae that live in their tissues and feed them. Without the algae, corals may starve and die.
oil spill: A release of petroleum into the environment, especially the ocean, from tankers, pipelines or drilling. Oil coats animals, destroying the insulation of feathers and fur, and poisons them.
microplastics: Plastic pieces smaller than 5 millimeters, from larger plastic broken down by sunlight and waves, fibers from clothing, and small beads. Animals eat them, and they carry toxic chemicals into food webs.

8.3 Endocrine Disruptors

Endocrine disruptors are chemicals that interfere with hormones by mimicking them, blocking their receptors or changing how much is made. Atrazine, BPA, phthalates and synthetic estrogens are examples. Even at very low doses they can cause intersex fish, abnormal frog development and human reproductive and developmental problems. Limits on use, extra cleaning steps at wastewater plants and safe medicine disposal reduce them.

An endocrine disruptor interferes with hormones: it mimics a hormone, blocks its receptor, or changes how much is made.
Examples: the herbicide atrazine, BPA and phthalates in some plastics, and synthetic estrogen from birth control pills that passes into wastewater.
Effects: intersex fish, frogs with abnormal sex organs, thinner eggshells, and in people reproductive, developmental and some cancer risks. Effects can appear at very low doses.
Reduce them by limiting their use, extra cleaning steps at wastewater plants, proper disposal of medicines, and safer substitutes.

the cells switch on growth, development or reproduction it binds the receptor and sends a false signal, or blocks the real hormone reproductive organs, growth and behavior develop abnormally fish, frogs and other wildlife downstream show intersex and reproductive effects

endocrine disruptor: A chemical that interferes with the body's hormones by mimicking them, blocking their receptors, or changing how much is made. Examples include atrazine, BPA, phthalates and synthetic estrogens.

8.4 Human Impacts on Wetlands and Mangroves

Wetlands and mangroves provide valuable ecosystem services: they store floodwater, recharge groundwater, filter pollutants, store carbon, buffer coasts against storm surge and shelter fish and birds. Draining and filling them for development and farms, and clearing mangroves for shrimp ponds, removes these services, raising flood and storm damage and lowering water quality. Permits, mitigation and restoration protect them.

Ecosystem services of wetlands: store floodwater, recharge groundwater, filter pollutants and sediment, store carbon, and give habitat and nurseries for fish and birds.
Mangroves protect coasts from storm surge and erosion with their dense roots, and shelter young fish.
Threats: wetland drainage and filling for development and farms, dams and water diversion, pollution, and clearing mangroves for shrimp aquaculture.
Protection: laws such as the Clean Water Act permit process, mitigation (avoid, minimize, restore), conservation easements and restoration.

their plants, soils and water storage are lost downstream flooding becomes more frequent and severe more sediment, nutrients and pollutants reach rivers and coasts storm surges and waves reach homes with more force, and nursery habitat for fish is lost

storm surge: A rise in sea level pushed onto the coast by a storm's winds and low pressure. Mangroves, marshes and barrier islands reduce its height and force before it reaches homes.
wetland drainage: Removing water from a wetland with ditches, pipes or fill so the land can be farmed or built on. It destroys wetland habitat and the services wetlands provide, such as flood storage and water filtering.

8.5 Eutrophication

Cultural eutrophication happens when nitrogen and phosphorus from fertilizer, manure and sewage enter water. The extra nutrients feed an algal bloom that shades plants below; when the algae and plants die, decomposers use oxygen to break them down, dissolved oxygen falls, and fish and bottom animals die in hypoxic dead zones. Keeping nutrients on the land and out of water prevents it.

Eutrophication is the enrichment of water with nutrients. Cultural eutrophication is the fast, human-caused kind, from fertilizer, manure, sewage and detergents.
The chain: nutrients, then an algal bloom, then die-off, then decomposition that uses oxygen, then low dissolved oxygen (hypoxia), then fish kills. Name every link.
Oligotrophic lakes are low in nutrients, clear and oxygen-rich; eutrophic lakes are high in nutrients, green and low in deep-water oxygen.
Fixes keep nutrients out: buffer strips, careful fertilizer use, cover crops, wetland restoration, nutrient removal at wastewater plants and phosphate-free detergents.

the limiting nutrients for algae are no longer in short supply an algal bloom forms and shades out plants below decomposers break them down dissolved oxygen in the deeper water falls fish die or leave and bottom animals die: a dead zone

eutrophication: The enrichment of a body of water with nutrients, especially nitrogen and phosphorus, which leads to excess algae growth. Cultural eutrophication is the rapid kind caused by human sources such as fertilizer and sewage. An oligotrophic lake is low in nutrients; a eutrophic one is high.
algal bloom: A rapid increase in algae in water, often fed by extra nutrients. Blooms turn water green, block sunlight, and when they die their decomposition uses up dissolved oxygen. Some, called harmful algal blooms, release toxins.
hypoxia: A state of very low dissolved oxygen in water, below what most fish and bottom animals need. Large hypoxic areas are called dead zones, such as the one in the Gulf of Mexico.

8.6 Thermal Pollution

Thermal pollution is heat added to water by people, mostly from power plant and factory cooling water and from warm runoff. Warmer water holds less dissolved oxygen while raising the oxygen needs of fish, so cold-water species decline, and sudden changes cause thermal shock. Cooling towers and ponds, shade along streams and temperature limits reduce it.

Thermal pollution is heat: a harmful rise in water temperature caused by people. Main sources: power plant and factory cooling water, warm runoff from pavement, and cutting shade trees along streams.
Warm water holds less dissolved oxygen, while warm fish need more. Warmth can also feed algae and spread disease.
Thermal shock: a sudden temperature change that organisms cannot adjust to, such as a plant suddenly starting or stopping its discharge.
Fixes: cooling towers and cooling ponds that release heat to the air, shade trees on stream banks, and limits on discharge temperature.

the water returns to the river warmer than it was oxygen in the river falls below the outlet they need more oxygen just as less is available trout and other cold-water species die or leave; sudden changes cause thermal shock

thermal pollution: A harmful rise in the temperature of a body of water caused by people, mainly from power plant and factory cooling water and warm urban runoff. Warmer water holds less dissolved oxygen.
thermal shock: A sudden change in water temperature that organisms cannot adjust to, such as when a plant starts or stops releasing warm water. It can kill fish and other aquatic life.

8.7 Persistent Organic Pollutants (POPs)

Persistent organic pollutants are synthetic, carbon-based chemicals such as DDT, PCBs and dioxins that resist breakdown, dissolve in fat, travel long distances on wind and water and stay toxic for decades. They collect in cold regions and in animal fat, harming reproduction and development; DDT thinned the eggshells of birds of prey. Bans such as the Stockholm Convention cut new inputs, but levels fall slowly.

A persistent organic pollutant (POP) is a synthetic, carbon-based chemical that resists breakdown, dissolves in fat, travels long distances and is toxic.
Examples: DDT and other old pesticides, PCBs from electrical equipment, and dioxins from burning plastics and some industrial processes.
POPs collect in cold regions far from where they were used, and they are stored in fat, so they build up in animals over time.
Harm: thin eggshells (DDT in birds of prey), reproductive and immune problems, some cancers. The Stockholm Convention (2001) restricts them worldwide.

it enters soil, water and air it persists for years to decades it travels long distances and collects in the Arctic animals store it in fatty tissue instead of excreting it it harms reproduction, development and the immune system, as DDT did to birds of prey

persistent organic pollutant: A persistent organic pollutant: a synthetic, carbon-based chemical that resists breakdown, dissolves in fat rather than water, travels long distances and is toxic. DDT, PCBs and dioxins are examples.
DDT: DDT: a persistent insecticide widely used from the 1940s, banned for most uses in the United States in 1972. It caused thin eggshells in birds of prey. PCBs (polychlorinated biphenyls) are persistent industrial chemicals once used in electrical equipment.

8.8 Bioaccumulation and Biomagnification

Bioaccumulation is the build-up of a persistent, fat-soluble pollutant in one organism over its life. Biomagnification is the rise in its concentration at each higher trophic level, because each consumer eats many organisms and keeps their stored pollutant. DDT, PCBs and methylmercury reach their highest levels in top predators, thinning eggshells in birds of prey and leading to fish advisories for people.

Bioaccumulation: a substance builds up in one organism over its life, because it is taken in faster than it is removed.
Biomagnification: the concentration rises at each higher trophic level of a food chain. Top predators carry the most.
Substances that do this are persistent and fat-soluble: DDT, PCBs and methylmercury, which bacteria make from mercury released by sources such as burning coal and small-scale gold mining.
Effects: DDT thinned eggshells of eagles, ospreys and pelicans; mercury harms the developing nervous system, so fish advisories limit meals of large predatory fish.

producers and small organisms absorb it and store it in fat its body concentration rises over its life: bioaccumulation it takes in all their stored pollutant, while much of the food's mass is used for energy the concentration multiplies up the chain: biomagnification they suffer harm, such as thin eggshells in birds of prey, and people who eat top predator fish are exposed

bioaccumulation: The build-up of a substance in one organism over its lifetime, because it is taken in faster than it is broken down or excreted. Persistent, fat-soluble substances bioaccumulate.
biomagnification: The increase in concentration of a persistent, fat-soluble substance at each higher trophic level of a food chain, so top predators carry the highest levels.
methylmercury: A toxic form of mercury made by bacteria in water and sediment from mercury released by sources such as coal burning and small-scale gold mining. It bioaccumulates and biomagnifies in fish and harms the developing nervous system.

8.9 Solid Waste Disposal

Municipal solid waste in the United States is mostly landfilled (about half in 2018), with the rest recycled, composted or burned. Sanitary landfills use liners, leachate collection, soil cover, gas wells and caps to contain trash; buried organic waste decomposes slowly without oxygen and makes methane. Incineration cuts volume but releases air pollutants and ash. E-waste needs special handling, and ocean dumping is banned.

Municipal solid waste is everyday trash from homes and businesses. In 2018 (EPA) about 50% was landfilled, 32% recycled or composted, and 12% burned for energy.
A sanitary landfill has a clay and plastic liner, leachate collection pipes, daily soil cover, gas wells and a final cap. Leachate is liquid that seeps through trash and picks up pollutants.
Buried organic waste decomposes slowly without oxygen and makes methane. Incineration cuts volume about 90% and can make power, but releases air pollutants and toxic ash.
E-waste holds lead, mercury and cadmium and needs special handling. Ocean dumping of trash is banned in the United States.

about half goes to landfills in the United States it dissolves chemicals and becomes leachate, which a liner and pipes must catch methane and CO2 form; gas wells collect the methane to burn or use for power it decomposes very slowly, so landfills fill up and must be managed for decades

municipal solid waste: Municipal solid waste (MSW): everyday trash from homes, schools and businesses, such as paper, food, yard waste, plastics, metals and glass. It does not include industrial, mining or farm waste.
sanitary landfill: An engineered site for burying solid waste, with a clay and plastic liner, leachate collection pipes, daily soil cover, methane gas wells and a final cap, designed to keep waste, liquid and gas from escaping.
leachate: Liquid that forms when water seeps through buried waste and dissolves chemicals from it. Landfill liners and pipes collect it so it does not pollute groundwater.
incineration: Burning solid waste at high temperature. It reduces waste volume by about 90% and can generate electricity (waste-to-energy), but releases air pollutants and leaves ash that may be toxic.
e-waste: Discarded electronics such as phones, computers and televisions. They contain toxic metals such as lead, mercury and cadmium as well as valuable metals, so they need special recycling or disposal.

8.10 Waste Reduction Methods

Waste is reduced by following the hierarchy: reduce first (less packaging, durable goods), then reuse, then recycle and compost, then recover energy, with landfilling last. Recycling saves materials and energy but has costs; composting turns food and yard waste into soil and avoids landfill methane. Policies such as pay-as-you-throw, bag fees and deposits shift behavior, and landfill gas can generate electricity.

The waste hierarchy: reduce, reuse, recycle and compost, recover energy, then landfill. The earlier steps save the most.
Source reduction means making less waste in the first place: less packaging, durable products, buying only what is needed.
Recycling saves resources and energy (aluminum about 95%) but costs money to collect and sort; some plastics have weak markets. Composting turns food and yard waste into humus and avoids landfill methane.
Other tools: landfill gas capture for electricity, e-waste recycling, and policies such as deposits, bag fees and pay-as-you-throw.

less waste is created at all fewer new products must be made, saving materials and energy less goes to landfills, less ore is mined, and less landfill methane forms some energy is recovered from waste that could not be avoided

source reduction: Reducing waste before it is created, for example by designing products with less packaging, making durable goods, or buying only what is needed. It is the most preferred step in the waste hierarchy.
recycling: Collecting used materials such as aluminum, paper, glass and some plastics and processing them into new products. It saves resources and energy but costs money and energy to collect and sort.
composting: Letting microbes break down food scraps, yard waste and paper with oxygen to make humus-rich compost for soil. It keeps organic waste out of landfills, where it would make methane.
landfill gas: The methane and CO2 produced when buried waste decomposes without oxygen. Landfills can capture it with wells and burn it to generate electricity (landfill gas to energy), a form of landfill mitigation.

8.11 Sewage Treatment

Sewage treatment cleans wastewater in stages. Primary treatment physically removes solids as sludge; secondary treatment uses microbes in aerated tanks to break down dissolved organic matter and cut BOD; tertiary treatment removes nitrogen and phosphorus; disinfection kills germs. Sludge is digested and disposed of or reused. Septic systems treat wastewater for single homes, and combined sewers can overflow in storms.

Primary treatment: physical. Screens, grit chambers and settling tanks remove solids as sludge.
Secondary treatment: biological. Microbes in aerated tanks break down dissolved organic matter, cutting BOD so the river keeps its oxygen.
Tertiary treatment: removes nitrogen and phosphorus (preventing eutrophication) and other chemicals. Then disinfection with chlorine, ozone or UV kills germs.
Homes without sewers use a septic system: a tank where solids settle and a drain field where soil filters the liquid. Combined sewers can overflow untreated sewage in heavy rain.

large objects, grit and much of the solid matter are removed as sludge BOD falls, so the waste will not use up the river's oxygen nutrients that would feed algal blooms are kept out of the river germs are killed before the water is released methane can be captured for energy and solids are landfilled, burned or spread as fertilizer

sewage treatment: The process of cleaning wastewater from homes and businesses before it is released, in stages: primary (physical), secondary (biological), tertiary (nutrient and chemical removal) and disinfection.
primary treatment: The first, physical stage of sewage treatment: screens and grit chambers remove debris and sand, and settling tanks let solids sink as sludge while grease is skimmed off.
secondary treatment: The biological stage of sewage treatment: microbes in aerated tanks break down dissolved organic matter, greatly reducing its biochemical oxygen demand (BOD).
tertiary treatment: Extra treatment after the secondary stage that removes nutrients such as nitrogen and phosphorus, and sometimes other chemicals, using filters and chemical or biological processes.
sludge: The solid material removed from wastewater during treatment. It is usually digested by microbes (which can make methane for energy), then dried and landfilled, burned or used as fertilizer.
septic system: A wastewater system for a single home: an underground tank where solids settle and bacteria break some down, and a drain field where soil filters the liquid that flows out.

8.12 Lethal Dose 50% (LD50)

LD50 is the dose, in milligrams per kilogram of body mass, that kills half of a test population; it is read off a graph of percent killed against dose at the 50% line. The lower the LD50, the more toxic the substance. Multiply the LD50 by a body mass to get a whole-body dose, writing the units so kilograms cancel, and convert milligrams to grams when asked.

Toxicity is how harmful a substance is. The dose is how much enters the body, usually in milligrams per kilogram of body mass (mg/kg).
LD50 is the dose that kills 50% of a test population. A lower LD50 means a more toxic substance.
Whole-body dose: $\text{LD}_{50} \times \text{body mass}$ , for example $40\,\frac{\text{mg}}{\text{kg}} \times 0.25\,\text{kg}$ $= 10\,\text{mg}$ . Write the units so kilograms visibly cancel.
LD50s come from animal tests, so they only estimate the effect on people, and they say nothing about harm that does not kill.

a larger percent of each group dies the dose under that point is the LD50 it is more toxic and gets a stronger warning label gives the whole-body dose in milligrams for an animal of that size

dose: The amount of a substance that enters an organism, usually given in milligrams per kilogram of body mass (mg/kg) so animals of different sizes can be compared.
toxicity: How harmful a substance is to living things. A toxicant is a substance that causes harm; the smaller the dose needed to cause harm, the higher the toxicity.
LD50: Lethal dose 50%: the dose, in mg per kg of body mass, that kills half of a test population. A lower LD50 means a more toxic substance.

8.13 Dose Response Curve

A dose-response curve shows the percent of a test group responding at each dose. It is flat at zero below the threshold dose, rises steeply through 50% and levels off near 100%. Read across from 50% and down to find the LD50 (deaths) or ED50 (another effect). The substance whose curve rises at lower doses is more toxic, and harm can begin far below the LD50.

A dose-response curve plots dose (mg/kg) on the horizontal axis against the percent of a test group responding on the vertical axis. It is usually S-shaped.
The threshold dose is where the curve leaves zero: the highest dose with no observed response.
The LD50 is read at 50% on a curve of deaths. The ED50 (effective dose 50%) is read at 50% on a curve of a nonlethal effect, such as illness or sleep.
To compare substances, compare where their curves rise: the curve to the left belongs to the more toxic substance.

the test group shows no measurable response, so the curve sits at zero affects a larger percent of the group, and the curve rises steeply through 50% gives the LD50 for deaths or the ED50 for another effect belongs to the more toxic substance

dose-response curve: A graph of the percent of a test population responding (for example, dying) against the dose. It is usually S-shaped and is used to read the threshold dose, the LD50 and the ED50.
threshold dose: The highest dose at which no response is observed in a test population; on a dose-response curve, the point where the curve leaves zero.
ED50: Effective dose 50%: the dose that causes a chosen nonlethal effect, such as illness or sleep, in half of a test population.

8.14 Pollution and Human Health

Linking a pollutant to a disease is hard because people face many exposures over long times. Synergism means pollutants together can do more harm than their effects added. Acute effects follow short, high exposures; chronic effects follow long ones. Know ground-level ozone and lung function, asbestos and mesothelioma, and sewage-contaminated water and dysentery.

Cause and effect are hard to prove in people: exposures are mixed and long, other factors vary, and many diseases take years to appear.
Synergism: two or more substances together cause more harm than the sum of their separate effects.
Acute effects follow a short, high exposure quickly. Chronic effects follow long or repeated exposure and may take years to appear.
Examples to know: ground-level ozone lowers lung function and triggers asthma; asbestos causes mesothelioma; untreated sewage in drinking water spreads dysentery.

it is hard to link one illness to one pollutant can cause more harm together than their separate effects add up to (synergism) causes acute effects soon after, such as dizziness or an asthma attack causes chronic effects that may appear years later, such as mesothelioma

synergism: An interaction in which two or more substances together cause more harm than the sum of the harm each causes alone (a synergistic effect).
acute exposure: Acute exposure is short, often a single high dose, with effects soon after (an acute effect). Chronic exposure is long or repeated, often at low doses, with effects that may take months or years to appear (a chronic effect).

8.15 Pathogens and Infectious Diseases

Pathogens are bacteria, viruses, protozoa, fungi and worms that cause infectious diseases. They spread through water, air, food, contact and vectors such as mosquitoes and fleas. Poor sanitation and crowding speed the spread, which is why clean water and sewage treatment prevent cholera. A warming climate can widen the range of vectors and the diseases they carry.

A pathogen causes disease: bacteria, viruses, protozoa, fungi and parasitic worms. An infectious disease is one that can spread to new hosts.
A disease vector is a living thing, often an insect, that carries a pathogen between hosts: mosquitoes (malaria, West Nile virus, Zika virus), fleas (plague).
Routes to know: waterborne (cholera, dysentery), airborne (tuberculosis; SARS and MERS are respiratory viruses that jumped from animals), vector-borne (malaria, plague, West Nile, Zika).
Climate change can spread vectors to new latitudes and elevations; floods can push sewage into drinking water.

it multiplies and causes an infectious disease the disease spreads to new hosts make spread easier, so developing countries carry much of the burden lets vectors such as mosquitoes survive in new places, widening the disease’s range

pathogen: A living thing or virus that causes disease in its host: a bacterium, virus, protozoan, fungus or parasitic worm.
infectious disease: A disease caused by a pathogen that can spread from one host to another, through water, air, food, contact or a vector.
disease vector: A living thing, often an insect such as a mosquito or flea, that carries a pathogen from one host to another. A vector-borne disease spreads this way.
malaria: Infectious diseases to know: malaria (protozoan, mosquitoes), tuberculosis (bacterium, airborne), cholera (bacterium, contaminated water), plague (bacterium, fleas), West Nile virus and Zika virus (mosquitoes), and SARS and MERS (respiratory viruses that passed from animals to people).