Khan Academy + FiveAble Unit 8 Apes Notes

8.1 — Sources of Pollution

• Point Source Pollution: Directly identifiable sources such as sewage discharge pipes, drains, vehicle exhaustt

  • Legislation: Clean Water Act — unlawful for anyone to discharge any point source pollution without permits

    • Requires use of “Best Practicable Technology” (BPT) to clean point sources and “Best Available Technology” (BAT) to clean up toxins

    • Funds construction of several important facilities such as sewage treatment plants and includes provisions for protecting wetlands

    • Main goal of act: make all water “fishable and swimmable”

• Non-Point Source Pollution: Indirect sources such as agricultural runoff that are harder to trace and regulate, and are carried by water (runoff)

• Mercury and its compounds are highly toxic

  • Impacts nervous, digestive, immune systems, muscle coordination, vision, hearing, and speech

  • Small fraction of mercury is naturally emitted from volcanic eruptions, rock weathering, geologic springs, and ocean spray

  • Human activities that releases mercury: burning coal, incinerating trash, and mining

    • Since industrial revolution, mercury concentration has more than doubled

  • Mercury can bioaccumulate and biomagnify

    • Makes predatory fish at the top of the food chain extremely hazardous for human consumption due to methylmercury concentrations

  • Elemental sources of mercury + aquatic environments + bacteria in water = methylmercury

8.2 — Human Impacts on Ecosystems

• Aquatic pollution monitoring

  • Zone of tolerance: describes how different abiotic factors may impact the ability of an organism to live in an ecosystem (factors vary from sunlight to the amount of a pollutant in a water)

  • Some organisms have wider range of tolerance that others

    • More sensitive species called “Indicator Species” since they’ll be the first to disappear in an ecosystem under stress

• Monitoring water quality — key factors (dissolved oxygen, nutrient levels, presence of specific disease-causing organisms or toxins) are measured to determine the health of an aquatic ecosystem

  • DO — amount of oxygen in the water and that is available to organisms to carry out aerobic respiration

    

    • Cooler waters carry more dissolved oxygen

    • Added to ecosystems via moving water interacting with the air and the oxygen from photosynthetic organisms in the ecosystem

    • Removed from ecosystems through aerobic respiration

  • Oceanic dead zones — areas of low oxygen in the world caused by increased nutrient pollution

  • Biological oxygen demand (BOD) — how much DO is needed for all the organisms in the system to survive and thrive

    • If BOD exceeds DO in the system, the ecosystem is hypoxic (at an oxygen deficit)

    • Increases if there’s a large amount of organic waste that is decomposed by microbes using aerobic respiration

      • If there’s’ no DO — the water is anoxic

  • Oxygen sag curve — plot of DO vs. distance from a point source pollutant

    • Can help describe how much PPM (Parts per million) of oxygen that different species needs to survive

      
    

• Coral reefs suffer damage due to

  • Increasing ocean temperature

  • Sediment runoff

    • Sedimentation reduces light infiltration, affecting primary producers + visual predators

  • Destructive fishing practices

• Oil spills in marine water causes organisms to die from the hydrocarbons in the oil

  • Oil floats on the surface and coats the feathers of birds and marine mammals

  • Components of oil sink to ocean floor and kills bottom-dwelling organisms

  • Oil washing up on the beach has economic consequences on fishing/tourism industries

• Heavy metals used for industry (mining + burning of fossil fuels) can reach and leach into groundwater, impacting drinking water

8.3 — Endocrine Disruptors

• Endocrine disruptors — manmade or naturally occurring chemicals that affect the hormones within your body, also known as your endocrine system

  • Found in many daily used items such as plastic items, foods, and pesticides (BPA, triclosan, and perchlorate)

  • Causes unusual growth patterns and issues with reproduction

    • Risks of certain ailments and reproductive problems — Birth defects, gender imbalance, and issues with development

  • Plastic items can end up in oceans and get ingested by wildlife

  • Take LONG time to break down, leading to further damage as more organisms come into contact with the item

  • Effects on wildlife (higher levels of exposure → more concrete evidence of effects)

    • Egg thinning in birds

    • Imposex mollusks

    • Feminization in freshwater fish

    • Changes in reproduction of certain alligators and turtles

8.4 — Human Impacts on Wetlands and Mangroves

• Wetlands — areas where water covers the soil either part or all of the time

  • Provides a variety of ecological services: water purification, flood protection, water filtration, and habitat

  • Divided into 2 distinct groups:

    • Coastal/Tidal wetlands

      • Related to estuaries — areas where the water from the sea meets and mixes into freshwater

      • Differences in salinity makes it difficult for plants to grow except for mangroves (trees + shrubs that live in coastal intertidal zone)

    • Inland/Non-tidal wetlands

      • Near rivers, streams, lakes, and ponds

      • Includes swamps and marshes

• Importance of wetlands:

  • Water purification

    • Filters runoff before it reaches larger bodies of water + plants use the nutrients that wetlands trap

    • Actively traps greenhouse gases

  • Flood protection

    • Wetlands absorb large amounts of runoff water

    • When we alter wetlands by filling them up, we reduce their ability to reduce the effects of a torrential downpour

  • Habitat

    • Amphibians, certain fish and birds

• Threats to wetlands

  • Commercial development

    • Reduces ability to prevent floods

    • Destroys habitat

  • Dam construction

    • Diverts water and prevents it from reaching the wetlands → drains the wetlands → makes animals migrate away

    • Does not purify water

  • Overfishing

    • Low population in fish (keystone species) → massive reduction in other species

  • Pollutant runoff

    • Causes eutrophication from extra nutrients

    • Pollutants impacts the ability of fish to breathe due to contaminants

8.5 — Eutrophication

• Eutrophication — process by which a body of water becomes enriched in excess dissolved nutrients, typically phosphates and nitrates, leading to an overgrowth of aquatic plants and algae

  • Reduced dissolved oxygen levels

  • Algal blooms

  • Hypoxic water (low oxygen water) leads to death of fish and other aquatic organisms — mainly in coastal waterways and estuaries

  • Caused naturally, by human activities (agricultural runoff and discharge of wastewater and point/non-point sources

• Effects of eutrophication:

  • Algal blooms — algae growing rapidly

    • Excess algae/plants decomposing → more CO2 → lowers pH of seawater → OCEAN ACIDIFICATION

  • Dead zones — area of water that has low levels of DO due to decay of plant matter and is unable to support most forms of aquatic life in its hypoxic water

    • Void of natural plant and animal life

  • Biodiversity loss

    • More deadzones + overgrowth of plants → uninhabitable environments

  • Increased pH levels

• Eutrophic — high levels of nutrients within the water ways; characterized as containing large populations of aquatic organisms, but plants and algae grow to levels that can become a nuisance

• Oligotrophic — lakes with low levels of nutrients; characterized as supporting a low level of aquatic organisms; can be split into two layers during the summer — lower (hypolimnion) supports cold water organisms due to cold temperature

• Mesotrophic — lakes with moderate amounts of nutrients; has occasional algal blooms and if they’re deep enough, can also have hypolimnion near summer’s end (from sediments)

• Anthropogenic causes of eutrophication include agriculture, industrial activity, population growth (increased emissions of nitrogen and phosphorous)

• Stormwater facilities: designed to capture polluted runoff + catches excess nutrients and/or sediments before they reach fragile waterways

8.6 — Thermal Pollution

• Solubility of oxygen in water decreases as temperature increases (increased movement of water molecules makes it harder for oxygen molecules to dissolve in the water)

• Thermal pollution — increase in the temperature of a body of water, which can have a variety of negative effects on the ecosystem

  • Effects: decrease in solubility of oxygen in water → growth of harmful algal blooms and other organisms that thrive in low-oxygen environments

• Sources of thermal pollution:

  • Power plants: fossil fuels/nuclear energy usage discharges large amounts of heated water into nearby rivers, lakes, or oceans, raising the temperature of the water and harming fish, plants, and other aquatic life

  • Industrial facilities: factories, refineries, chemical plants, all use large amounts of water in their operations that gets heated and discharged into nearby waterways

  • Urbanization: expansion of cities and towns leads to paving over natural areas, causing heat island effect (surfaces absorb and retain heat, raising the temperature of the surrounding air and water)

  • Agriculture: irrigation and other farming activities contribute to thermal pollution by increasing temperature of water in nearby waterways

  • Recreational activities: swimming, boating, and water skiing raises temperatures of the water

  • Cooling towers: structures used to reject waste heat to the atmosphere through evaporative cooling that releases warm water as a byproduct

8.7 — Persistent Organic Pollutants (POPs)

• POPS — group of toxic chemicals that can remain in the environment for long periods of time and travel long distances through the air and water

  • Sources: industrial sources (PCBs — polychlorinated biphenyls), pesticides (DDT — dichlorodiphenyltrichloroethane and HCB — hexachlorobenzene), incineration and other combustion processes (releases dioxins and furans), natural sources (dioxins from forest fires/volcanic eruptions), long-range transport, legacy sources

  • Fat soluble (dissolves in fats and oils) — accumulates in the fatty tissues of animals, including humans, rather than being excreted from the body (BIOACCUMULATION)

    • Animals consume POPs → animal moves up food chain through consumption → POP accumulate in fat cells at higher trophic levels (BIOMAGNIFICATION)

  • Causes cancer, neurological disorders, developmental disorders

  • Transport of POPs:

    • Airborne, waterborne, biomagnification, long-range transport, deposition

• Impacts of POPs

  • Environmental (thinning of bird eggshells, biomagnification)

  • Human health problems — cancer, neurological disorders, developmental problems, reproductive issues

  • Economic — impacts industries that rely on the natural resources that can be affected by POPs (e.g. fishing)

  • Social — displacement of communities and loss of livelihoods

  • International impacts — travels long distances through air and water, making them present in many areas, making it difficult to control

• Stockholm convention — legally binding treaty that aims to eliminate or restrict the production and use of POPs

  • Annex A — includes chemicals that are banned for production and use (DDT, Hexachlorobenzene and polychlorinated biphenyls)

  • Annex B — includes chemicals that are restricted for production and use (chlordane, dieldrin, and endrin)

  • Annex C — includes chemicals that are under review for possible inclusion in the future (PFOS and PFOA)

8.8 — Bioaccumulation and Biomagnification

• Biomagnification — process which toxins or pollutants become more concentrated as they move up the food chain

• Bioaccumulation — certain substances such as toxins or pollutants build up in the tissues of organisms over time

8.9 — Solid Waste Disposal

8.10 — Waste Reduction Methods

8.11 — Sewage Treatment

8.12 — Lethal Dose %50

8.13 — Dose Response Curve

8.14 — Pollution and Human Health

8.15 — Pathogens and Infectious Diseases