AP Environmental Science Notes

Unit 1 Introduction to Ecosystem

• Ecosystems

• Ecosystem: all living and nonliving things in an area

• Biome: large area with similar climate conditions that determine plant and animal species there

• Organism interactions –

  • Competition: organisms fighting over a resource like food or shelter; limits population size

  • Predation: one organism using another for energy source (hunters, parasites, even herbivores)

  • Mutualism: relationship that benefits both organism

  • Commensalism: relationship that benefits one organism and doesn’t impact the other

• Predation

  • Herbivores: (plant eaters) eat plants for energy

  • True predators: (carnivores) kill and eat prey for energy.

  • Parasites: use a host organism for energy, often without killing the host and often living inside host

  • Parasitoids: lay eggs inside a host organism; eggs hatch and larvae eat host for energy

• Symbiosis (sym = together | bio = living | osis = condition)

  • Any close and long-term interaction between two organisms of different species

    • Mutualism, commensalism, and parasitism are all symbiotic relationships.

• Competition: reduces population size since there are fewer resources available and fewer organisms can survive

  • Resource partitioning: different species using the same resources in different ways.

  • Temporal partitioning: using resources at different times, such as wolves and coyotes hunting at different times.

  • Spatial partitioning: using different areas of a shared habitat.

  • Morphological partitioning: using different resources based on different evolved body features.

  1. Terrestrial (Land) Biomes

• Biome: an area that shares a combination of average yearly temperature and precipitation (climate)

• The community of organisms (plants and animals) in a biome are uniquely adapted to live in that biome.

• Nutrient availability - plants need soil nutrients to grow, so availability determines which plants can survive in a biome.

• Shifting biomes - biomes shift in location on earth as climate changes.

  1. Aquatic Biomes

• Characteristics of Aquatic Biomes

  • Salinity: how much salt there is in a body of water, determines which species can survive and usability for drinking

  • Depth: influences how much sunlight can penetrate and reach plants below the surface for photosynthesis

  • Flow: determines which plants and organism can survive, how much O₂ can dissolve in water

  • Temperature: warmer water holds less dissolve O₂ so it can support fewer aquatic organisms

• Freshwater: Rivers and Lakes

  • Rivers have high O₂ due to flow mixing water and air also carry nutrient-rich sediments (deltas and flood plains = fertile soil)

  • Lakes = standing bodies of fresh H₂O (key drinking H₂O source)

    • Littoral: shallow water with emergent plants

    • Limnetic: where light can reach (photosynthesis)

      • No rooted plants, only phytoplankton

    • Profundal: too Deep for sunlight (no photosynthesis)

    • Benthic: murky bottom where inverts (bugs) live, nutrient-rich sediments

• Freshwater: Wetlands

  • Wetland: are with soil submerged/saturated in water for at least part of the year, but shallow enough for emergent plants

    • Plants living here have to be adapted to living with roots submerged in standing water (cattails, lily pads, reeds)

  • Benefits of wetlands

    • Stores excess water during storms, lessening floods.

    • Recharges groundwater by absorbing rainfall into soil.

    • Roots of wetland plants filter pollutants

    • Highly plant growth due to lots of water and nutrients (dead organic matter) in sediments

• Estuaries: areas where rivers empty into the ocean

  • Mix of fresh and salt water (species adapt to this)

  • High productivity (plant growth) due to nutrients in sediments deposited in estuaries by river.

  • Salt marsh:

    • Estuary habitat along coast in temperate climates

    • Breeding ground for man fish and shellfish species

  • Mangrove swamps:

    • Estuary habitat along coast of tropical climates

    • Mangrove trees with long, stilt roots stabilize shoreline and provide habitat for many species of fish and shellfish.

• Coral Reef

  • Warm shallow waters beyond the shoreline; most diverse marine biome on earth

  • Mutualistic relationship between coral (animals) and algae (plant

    • Coral takes CO₂ out of ocean to create calcium carbonate exoskeleton (the reef) and provides CO₂ to the algae.

    • Algae lives in the reef and provides sugar (energy) to the coral through photosynthesis.

      • Both species rely on the other:

        • Coral couldn’t survive without energy from algae.

        • Algae need the home of the reef of CO₂ from the coral.

• Intertidal Zones

  • Narrow band of coastline between high and low tide

  • Organisms must be adapted to survive crashing waves and direct sunlight/heat during low tide.

  • Shells and tough outer skin can prevent drying out (desiccation) during low tides.

    • Different organisms are adapted to live in different zones.

• Open Ocean

  • Low productivity/area as only algae and phytoplankton can survive in most of the ocean.

    • So large though, that algae and phytoplankton of ocean produce a lot of earth’s O₂ and absorb a lot of atmospheric CO_2.

  • Photic zone = area where sunlight can reach (photosynthesis)

  • Aphotic zone (abyssal) = area to deep for sunlight

  1. Carbon Cycle

• Movement of molecules that contain Carbon (CO₂, glucose, CH₄) between sources and sinks.

  • Some steps are very quick (FF combustion); some are very slow (sedimentation and burial)

  • Leads to imbalance in which reservoirs or sinks are storing carbon.

• The atmosphere is a key C reservoir, increasing levels of C in atmosphere. Leads to global warming.

• Carbon sink: a carbon reservoir that stores more carbon than it releases.

  • Ocean (algae and sediments), plants, soil

• Carbon source: processes that add C to atmosphere.

  • Fossil fuel (oil, coal, natural gas) combustion

  • Animal (cow burps and farts = CH₄)

  • Deforestation, releases CO₂ from trees

• Photosynthesis and Cellular Respiration

  • Both processes are very quick

  • Cycle C between biosphere and atmosphere in balanced amount (no net C increases in atmosphere)

  • Photosynthesis

    • Plants, algae, phytoplankton

    • Removes CO₂ from the atmosphere and converts it to glucose.

    • Glucose = biological form of C and stored (chemical) energy in form of sugar

    • CO₂ sink

  • Cellular Respiration

    • Done by plants and animals to release stored energy.

    • Uses O₂ to break glucose down and releases energy.

    • Releases CO₂ into atmosphere

    • CO₂ source (adds CO₂ to atmosphere)

• Ocean and Atmosphere

  • Direct exchange: CO₂ moves directly between atmoshpere and the ocean by dissolving into and out of ocean water at the surface

    • Happens very quickly and in equal directions, balancing levels of CO₂ between atmosphere and ocean

  • Because of direct exchange, increasing atmospheric CO₂ also increases ocean CO₂, leading to ocean acidification

  • Algae and phytoplankton take CO₂ out of the ocean and atmosphere through photosynthesis

    • Coral reef and marine organisms with shells also take CO₂ out of the ocean to make calcium carbonate exoskeletons

  • Sedimentation: when marine organisms die, their bodies sink to the ocean floor where they’re broken down into sediments that contain C

    • Burial: over long, periods of time, pressure of water compresses C – containing sediments on the ocean floor into sedimentary stone (limestone, sandstone) - long term C reservoir

• Burial, Extraction, and Combustion

  • Burial: slow, geological process that stores C in underground sinks like sedimentary rock or fossil fuels

    • Sediments (bits of rock, soil, organic matter) compressed into sedimentary rock or fossil fuels by pressure from overlying rock layers or water.

  • Fossil Fuels (FF): coal, oil, and natural gases are formed from fossilized remains of organic matter.

  • Extraction and Combustion: digging up or mining fossil fuels and burning them as energy source, releases CO₂ into the atmosphere

  • Burial (formation of fossil fuels) takes far longer than extraction and combustion, which means they increase concentration of CO₂ in the atmosphere

  1. Nitrogen Cycle

• Movement of Nitrogen containing molecules between sources and sinks/reservoirs

  • Sources releases N into atmosphere; sinks take N out of the atmosphere in increasing amounts.

• Nitrogen reservoirs hold nitrogen for relatively short periods of time compared to the Carbon cycle.

• Atmosphere = main Nitrogen reservoir

  • Nitrogen in the atmosphere exists mostly as N₂ gas, not usable by plants or animas.

• Nitrogen = critical plant and animal nutrient

  • All living things need nitrogen for DNA and amino acids to make proteins.

• Nitrogen fixation

  • Process of N₂ gas being converted into biologically available (useable by plants) NH₃ (ammonia) or NO₃^- (nitrate)

  • Bacterial fixation: certain bacteria that live in the soil, or in symbiotic relationships with plant root nodules convert N₂ into ammonia (NH₃)

  • Synthetic fixation: humans combust fossil fuels to convert N₂ gas into nitrate (NO₃^-)

• Other Nitrogen Cycle Steps

  • Assimilation: plants and animals taking nitrogen in and incorporating it into their body

  • Ammonification: soil bacteria, microbes and decomposers converting waste and dead biomass back into NH₃ and returning it to soil

  • Nitrification: conversion of NH₄ into nitrite (NO₂) into nitrous oxide (N₂O) gas which returns to atmosphere

• Human impacts on nitrogen cycle

  • Climate: N₂O (nitrous oxide) = greenhouse gas which warms earth’s climat4

  • Ammonia volatilization: excess fertilizer use can lead to NH₃ gas entering the atmosphere.

  • Leaching and eutrophication: synthetic fertilizer use leads to nitrates (NO₃^-) leaching, or being carried out of soil by water.

  1. Phosphorus Cycle

• Phosphorus cycle basics

  • Movement of phosphorus atoms and molecules between sources and sinks/reservoirs

    • Rocks and sediments containing phosphorous minerals = major reservoirs

  • Phosphorus cycle is very slow compared to Carbon, water, nitrogen cycles.

  • Takes a long time for phosphorus minerals to be weathered out of rocks and carried into soil/bodies of water.

  • No gas phase of phosphorus (doesn’t enter atmosphere)

  • Because the cycle is so slow, it is limiting nutrients, meaning plant growth in the ecosystem is often limited by phosphorus availability in soil and water.

  • Phosphorus is needed by all organisms for DNA, ATP (energy), bones and tooth enamel in some animals.

• Phosphorus sources

  • The major natural source of phosphorus is the weathering of rocks that contain phosphorus materials.

    • Wind and rain break down rock and phosphate are released and dissolved into water’ rainwater carries phosphates into nearby soils and bodies of water

    • Weathering is so slow that phosphorus is often a limiting nutrient in aquatic and terrestrial ecosystems.

  • Synthetic: (human) sources of phosphorus = mining phosphate minerals and adding to products like synthetic fertilizers and detergents/cleaners

    • Synthetic fertilizers containing phosphates are added to lawns or agriculture. Field: runoff carries phosphorus into nearby bodies of water. Phosphates from detergents and cleaners enter bodies of water via wastewater from homes.

• Assimilation and Excretion/decomposition

  • Phosphorus is absorbed by plant roots and assimilates into tissues; animals assimilate phosphorus by eating plants or other animals.

    • Animal waste, plant matter and other biomass is broken down by bacteria/soil decomposers that return phosphate to soil.

    • Assimilation and excretion/decomposition form a mini loop within Phosphorus cycle just like assimilation and ammonification in nitrogen cycle, photosynthesis and respiration in carbon cycle.

• Sedimentation and Geography uplift

  • Phosphate doesn’t dissolve very well into water; much of it forms solid bits of phosphate that fall to the bottom as sediment (sedimentation)

    • Phosphorus sediments can be compressed into sediment rock over long time periods by pressure of overlying water.

  • Geological uplift: tectonic plate collision forcing up rock layers that form mountain; phosphorous cycle can start over again with weathering and release of phosphate from rock.

• Eutrophication (too much nitrogen and phosphorus)

  • Because they’re limiting nutrients in aquatic ecosystems, extra input of nitrogen and phosphorous lead to eutrophication (excess nutrients) which fuels algae growth.

    • Algae bloom covers surface of water, blocking sunlight and killing plants below surface.

    • Algae eventually die-off: bacteria that break down dead algae use up O₂ in the water (because decomposition = aerobic process)

    • Lower O₂ levels (dissolved oxygen) in water kills aquatic animals, especially fish.

    • Bacteria use up even more O₂ to decompose dead aquatic animals.

    • Create positive feedback loop: less O₂ 🡪 more dead organism 🡪 more bacterial decomposition 🡪 O_2.

  1. Hydrologic (water) Cycle

• Water cycle overview

  • Movement of H₂O (in different states) between sources and sinks

  • States of matter (solid/liquid/gas) as well as where water is moving are ley in H₂O cycle.

  • Energy from sun drives the H₂O cycle.

  • Ocean = largest water reservoir

  • Ice caps and groundwater are smaller reservoirs but contain fresh useable water for humans.

• Evaporation and Evapotranspiration

  • 2 main sources of water (processes that cycle it from liquid on earth back into the atmosphere)

  • Sometimes called vaporization since liquid water becomes water vapor (gas) in atmosphere.

  • Transpiration: process plants use to draw groundwater from roots up to their leaves

    • Leaf openings called stomata open, allowing water to evaporate into atmosphere form leaf.

    • Movement of H₂O out of leaf creates low H₂O potential in leaf, pulling H₂O up from roots.

  • Evapotranspiration: amount of H₂O that enters atmosphere from transpiration and evaporation combined

  • Both processes are driven by energy from the sun

• Runoff and Infiltration

  • Precipitation (rain) either flows over earth’s surface into a body of water (runoff) or trickles through soil down into groundwater aquifers (infiltration)

  • Groundwater (aquifers) and surface waters (lakes/rivers) are important freshwater reservoirs for humans and animals.

  • Precipitation recharges groundwater through infiltration, but only if ground is permeable (able to let water pass through)

  • Runoff recharges surface waters, but can also carry pollutants into water sources.

  1. Primary Productivity

• Primary Productivity Basics

  • Primary Productivity: rate that solar energy is converted into organic compounds via photosynthesis over a unit of time.

    • (Rate of photosynthesis of all producers in an area over a given period of time

  • Ecosystems with primary productivity are usually more biodiverse than ecosystems with low primary productivity.

• Calculating Primary Productivity

  • NPP = GPP – RL

  • Net primary productivity (NPP): the amount of energy (biomass) leftover for consumers after plants have used some for respiration.

    • Think of NPP as the actual amount of the plants paycheck it keeps after taxes.

  • Respiration loss (RL): plants use up some of the energy they generate via photosynthesis by doing cellular respiration (movement, internal transportation, etc.)

  • Gross Primary Productivity (GPP): the total amount of sun energy (light) that plants capture and convert to energy (glucose) through photosynthesis.

• Ecological Efficiency

  • The portion of incoming solar energy that is captured by plants and converted into biomass (NPP or food available for consumers)

  • Generally, only 1% of all incoming sunlight is captured and converted into GPP via photosynthesis.

  • Of that 1%, only about 40% (or o.4% of total incoming solar energy) is converted into biomass/plant growth (NPP)

  • Some ecosystems are more efficient (higher NPP) than others.

• Trends in Productivity

  • The more productive a biome is, the wider the diversity of animal life it can support.

  • Water availability, higher temperature, and nutrient availability are all factors that lead to high NPP.

  1. Trophic Levels

  2. The 10% Rule

• Conservation of Matter and Energy

  • Matter and energy are never created or destroyed; they only change forms.

  • 1^st law of thermodynamics: energy is never created or destroyed.

  • Biogeochem cycles demonstrates conservation of matter (C/N/H₂O/P)

  • Food webs demonstrate conservation of energy.

• 2^nd Law of Thermodynamics

  • Each time energy is transferred, some of it is lost as heat.

    • Applied to food webs: the amount of useable energy decreases as you move up the food chain (organism use up most of it for movement, development, etc.)

  • Because available energy decreases with each step up the food chain, trophic pyramid (troph = nourishment or growth) is used to model how energy moves through an ecosystem

  • 10% Rule: in trophic pyramids, only about 10% of the energy from one level makes it to the next level; the other 90% is used by the organism and lost as heat.

• Trophic Levels and 10% Biomass

  • Tertiary consumers: animals that eat secondary consumers or carnivores and omnivores (aka top/apex predators)

  • Secondary consumers: animals that eat primary consumers or herbivores (aka – carnivores and omnivores)

  • Primary consumers: animals that eat plants (herbivores)

  • Producers: (plants) “produce” – really convert sun’s light energy into chemical energy (glucose)

  • 10% rule also applies to biomass (or mass of all living things at each trophic level)

    • Since energy is needed for growth and only 10% of energy transfers from one level to the next, only 10% of the biomass can be grown/supported.

• To calculate biomass or energy available at the next level up, move the decimal place one spot to the left (or divide by 10)

  1. Food Chains and Food Webs

• Food Web Basics

  • Shows how matter and energy flow through an ecosystem, from organism to organism.

  • When one organism preys on (eats) another, the matter (C/N/H₂O/P) and energy (glucose, muscle tissue, etc.) are passed on to the predator.

  • Arrows in food webs indicate direction of energy flow.

• Food Web vs Chain

  • The food chain just shows one, linear path of energy and matter.

  • Food webs have at least 2 different interconnected food chains

• Interactions and Trophic Cascade

  • Food webs show how increases or decreases in population size of a given species impact the rest of the food web.

  • Trophic cascade: removal or addition of a top predator has a ripple effect down through lower trophic levels

Unit 2 Biodiversity

2.1 Intro to Biodiversity

• Biodiversity Basics

  • Diversity of life forms in an ecosystem; measured on 3 different levels:

    • Ecosystem diversity: the number of different habitats available in each area.

    • Species diversity: the number of different species in an ecosystem and the balance or evenness of the population sizes of all species in the ecosystem

    • Genetic diversity: how different the genes are of individuals within a population (group of the same species)

      • Higher biodiversity = higher ecosystem/ population health

• Species Richness and Evenness

  • Richness: the total number of different species found in an ecosystem

  • Evenness: measure of how all the individual organisms in an ecosystem are balanced between the different species

    • Indicates if there are one or two dominant species, or if population size is well balanced.

• Genetic diversity is Beneficial.

  • Genetic diversity: measure of how different the genomes (set of genes) are of the individuals within a population of a given species.

  • The more genetic diversity in a population, the better the population can respond to the environment. Stressors like drought, disease, or famine.

  • More genetic diversity = a higher chance that some of the individuals in a population have traits that allow them to survive the environmental stressor.

• Bottleneck Event

  • An environmental disturbance (natural disaster/ human habitat destruction) that drastically reduces population size and kills organisms regardless of their genome.

  • Surviving population is smaller because individuals died randomly, it doesn’t represent the genetic diversity of the original population.

  • Bottleneck events reduce genetic diversity – because the population is smaller and less genetically diverse, it’s even more vulnerable to future environmental disturbances.

• Inbreeding Depression

  • Inbreeding is when an organism mates with closely related “family” members.

    • Leads to a higher chance of offspring having harmful genetic mutations because they’re getting similar genotypes from both parents.

  • Smaller populations are more likely to experience inbreeding.

• Ecosystem Resilience

  • Resilience: the ability of an ecosystem to return to its original condition after a major disturbance (windstorm, fire, flood, clear-cutting, etc.).

  • Higher species diversity = higher ecosystem resilience

2.2 Ecosystem Services

• Goods that come from natural resources or services/functions that ecosystems carry out that have measurable economic/financial value to humans.

  • Provisioning: goods taken directly from ecosystems or made from natural resources (wood, paper, food)

  • Regulating: natural ecosystems regulate climate/air quality, reducing storm damage and healthcare costs

  • Supporting: natural ecosystems support processes we do ourselves, making them cheaper and easier (bees pollinate crops)

  • Cultural: money generated by recreation (parks, camping, tours) or scientific knowledge

• Humans Disrupt Ecosystem Services

  • Human activities disrupt the ability of ecosystems to function, which decreases the value of ecosystem services they proved.

    • This has ecological (natural) and economic (money-based) consequences.

• Provisioning Services

  • Goods/products directly provided to humans for sale/use by ecosystems.

  • Goods/products that are made from natural resources that ecosystems provide.

  • Disrupted by overharvesting, water pollution, clearing land for agriculture/urbanization.

• Regulation Services

  • Benefits provided by ecosystem processes that moderate natural conditions like climate and air quality.

  • Disrupted by deforestation.

• Supporting Services

  • Natural ecosystems support processes we do ourselves, making them less costly and easier for us.

  • Disrupted by pollinator habitat loss and filling in wetlands for development.

• Cultural Services

  • Revenue from recreational activities (hunting/fishing licenses, park fees, tourism-related spending) and profits from scientific discoveries made in ecosystems (health/agriculture/educational knowledge).

  • Disrupted by deforestation, pollution, and urbanization.

2.3 Theory of Island Biogeography

• Generalist- R: insects, reptiles, amphibians, fish (lay eggs and leave offspring)

• Specialist – K: mammals (bear, human, panda, whale, dolphin, etc.) (Stay with offspring for a while)

• Island Biogeography

  • Study of ecological relationships and community structure on islands.

  • Two basic “rules” or observations of island biogeography.

    • Larger islands support more total species.

      • The larger the island, the greater the ecosystem diversity.

      • Greater ecosystem diversity = more food and habitat resources.

      • More niches, or “roles” organisms can play in the ecosystem.

    • Islands closer to the “mainland” support more species.

      • Easier for colonizing organisms to get to the island from mainland.

      • More colonizing organisms = more genetic diversity in new population.

• Larger Islands Support More Species

  • Larger islands =

    • Higher ecosystem diversity

    • More available “niches” or roles

    • Larger population sizes (more genetically diverse and more resistant to environmental disturbance).

    • Lower extinction rate (species less likely to die off)

  • Positive correlation between island size and species richness

• Distance to Mainland

  • Closer to mainland = higher species richness

  • Easier for more species to migrate to island from mainland.

  • More continual migration of individuals to the island habitat.

    • Frequent migration brings more genetic diversity and larger population size.

  • Inverse relationship between island distance from mainland and species richness

    • The further away from mainland, the fewer species

• Evolution on Islands

  • Island have limited space and resources, creating unique conditions for evolution.

    • More pressure for species to adapt to narrower niches (more specific food/habitat).

  • Adaptive radiation: single species rapidly evolving into several new species to use difference resources and reduce competition.

  • Single colonizing species from mainland quickly evolves to many slightly different species to adapt to new island conditions.

2.4 Ecological Tolerance

• Ecological Range of Tolerance

  • Range of conditions such as temperature, salinity, pH, or sunlight that an organism can endure before injury or death results.

  • Species and individual organisms both have a range of tolerance for all the different environmental conditions of their habitat.

• Ecological Range of Tolerance – Zones

  • Optimal range: range where organism survive, grow, and reproduce.

  • Zone of physiological stress: range where organisms survive, but experience some stress such as infertility, lack of growth, decreased activity, etc.

  • Zone of intolerance: range where the organism will die.

• FRG Writing Tips

  • On FRQs about human activity or natural events that cause environmental disturbance, connect answer to ecological range of tolerance (if possible, connect human activity to climate change).

  • Try to connect a shift in range of tolerance to a specific kind of physiological stress.

2.5 Natural Disruptions to Ecosystems

• Natural disturbances

  • A natural event that disrupts the structure and or function of an ecosystem

    • Ex. Tornados, hurricanes, asteroids, forest fires, drought

  • Natural disturbance can be even greater than human disruptions. It can occur on periodic, episodic, or random time frames.

    • Periodic: occurs regular frequency (ex. Dry-wet seasons)

    • Episodic: occasional events with irregular frequency (ex. Hurricanes, droughts, fires)

    • Random: no regular frequency (ex. Volcanoes, earthquakes, asteroids)

• Natural Climate Change

  • Earth’s climate has varied over geologic time for numerous reasons.

  • Sea level has varied over geological time as glacial ice on earth melts and forms.

  • Increased CO₂ levels lead to warmer temperatures, melting of glacial ice and sea level rises.

• Environmental Change = Habitat Disruption

  • Major environmental disturbances result in widespread habitat changes and our loss.

• Migration

  • Wildlife may migrate to a new habitat as the results of natural disruptions.

    • Ex. Wildebeest migrating to follow rain patterns of African savanna.

      • Ocean species move further north as water temperature warms.

      • Bird migration and breeding shift earlier as insect hatching shifts earlier with warming climate.

2.6 Adaptations

• Fitness and Adaptation

  • All populations have some genetic diversity, or variability in genomes of individuals; genetic diversity exists because:

Random mutations while DNA is being copied create new traits.

• Crossing over in parent chromosomes creates new combinations of genes (and therefore traits).

  • Adaptation: a new trait that increases an organism’s fitness (ability to survive and reproduce).

• Adaptation and Natural Selection

  • Natural selection: organisms that are better adapted to their environment survive and reproduce more offspring

    • Individuals with adaptations pass them on to offspring and individuals without adaptations die off, which leads to the entire population having the adaptation over time (evolution).

      • Selective pressure/force: the environmental conditions that kills individuals without the adaptation.

• Environmental Change and Evolution

  • The environment an organism lives in determines which traits are adaptations.

    • As environments change, different traits may become adaptations and old traits become disadvantages.

• Pace of Evolution

  • The more rapidly the environment changes, the less likely a species in the environment will be to adapt to those changes.

    • If the pace of environmental change is too rapid, many species may migrate out of the environment or die-off completely.

  • The more genetic diversity in a population, the better they’re able to adapt to environmental change (higher chance that some individuals have good mutations).

2.7 Ecological Succession

• A Series of predictable stages of growth that a forest goes through.

• Two types of succession:

  • Primary succession: start from bare rock in an area with no previous soil formation.

    • Moss and lichen spores carried by the wind grow directly on rocks, breaking them down to from soil.

  • Secondary succession: starts from already established soil, in an area where a disturbance (fire, tornado, human land clearing) cleared out the majority of plant life.

    • Grasses, sedges, wildflowers, and berry bushes have seeds dispersed by wind or animal droppings.

• Stage of Succession

  • Stages are characterized by which type of plant species dominate the ecosystem; different species are adapted to the conditions of the different stages.

    • Pioneer or early succession species appear first, when the ground is simply bare rock, or bare soil after a disturbance.

      • Characteristics: seeds spread by wind or animals, fast growing, tolerant of shallow soil and full sunlight.

    • Mid-successional species appear after pioneer species helped develop deeper soil with more nutrients by their cycles of growth/death.

      • Characteristics: relatively fast growing, larger plants that need deeper soils with more nutrients than pioneers, sun tolerant.

    • Late successional or climax community species: appear last, after soil is deepened and enriched with nutrients by cycles of growth and death by early and mid-successional species.

      • Characteristics: large, slow-growing trees that are tolerant of shade and require deep soils for large root networks.

• Primary Succession

  • Occurs in an area that hasn’t previously been colonized by plants (bare rock)

  • Moss and lichen (spores dispersed by wind) are able to grow directly on rock by secreting acids that break down rock and release minerals containing nutrients they need,

• Secondary Succession

  • Occur in an area that already has established soil but has had most plant life removed by a disturbance.

  • Pioneer species: are still wind-dispersed seeds of plants that are fast-growing and sun-tolerant, but grasses/wildflowers/weed instead of moss/lichen.

  • Soil is already established and sometimes even enriched by nutrient-rich ash from fire, an overall, more rapid process than primary succession.

Unit 3 Population

3.1 Specialist vs. Generalist Species

• Specialist: smaller range of tolerance, or narrower ecological niche makes them more prone to extinction

  • Specific food requirements

  • Less ability to adapt to new conditions

• Generalist: larger range of tolerance, broader niche makes them less prone to extinction and more likely to be invasive

  • Broad food requirements

  • High adaptability

3.2 K-Selected and R-"Selected Species

• Quality vs. Quantity

  • K-selected – “Quality”

    • Few offspring, heavy parental care to protect them.

    • Usually reproduce many times

      • Ex. Most mammals, birds

    • Long lifespan, long time to sexual maturity = low biotic potential = slow population growth rate

      • More likely to be disrupted by environmental change or invasives.

  • R-selected – “Quantity”

    • Many offspring, little to no care

    • May reproduce only once.

      • Ex. Insects, fish, plants

    • Shorter lifespan, quick to sexual maturity = high biotic potential = high population growth rate

      • More likely to be invasive.

    • Better suited for rapidly changing environment conditions

  • K-Selected

    • Low biotic potential (repopulation rate) = hard for population to recover after disturbance

    • High parental care means death of parent = death of offspring

    • Invasives (usually r) outcompete for resources with high biotic potential and rapid population growth.

    • Less likely to adapt and more likely to go extinct.

  • R-Selected

    • High biotic potential (repopulation rate) = more rapid population recovery after disturbance

    • Low parental care means death of parent doesn’t impact offspring.

    • Not as impacted by invasive species since their population grows quickly.

      • More likely to be the invasive

      • Larger population and faster generation time = higher chance of adaptation and lower chance of extinction

3.3 Survivorship Curves

• Survivorship Curve: line that shows survival rate of a cohort (group of same-aged individuals) in a population from birth to death.

• Type I (mostly K-selected)

  • High survivorship early in life due to high parental care

  • High survivorship in mid life due to large size and defensive behavior

  • Rapid decrease in survivorship in late life as old age sets in

    • Ex. Most mammals

• Type II (in between R and K)

  • Steadily decreasing survivorship throughout life

• Type III (mostly R-selected)

  • High mortality (low survivorship) early in life due too little to no parental care

  • Few make it to midlife; slow, steady decline in survivorship in midlife.

  • Even fewer make it to adulthood, slow decline in survivorship in old age.

    • Ex. Insects, fish, plants

3.4 Carrying Capacity

• Carrying Capacity (k): the max number of individuals in a population that an ecosystem can support (based on limiting resources

  • Highest population size an ecosystem can support based on limiting resources:

    • Food

    • Water

    • Habitat (nesting sites, space)

  • Overshoot: when a population briefly exceeds carrying capacity

  • Consequences of overshoot: resource depletion

  • Die-Off: sharp decrease in population size when resource depletion (overshoot) leads to many individuals dying.

3.5 Population Growth and Resource Availability

• Population Characteristics

  • Size (N): total # of individuals in a given area at a given time

    • Larger = safer from population decline

  • Density: # of individuals/area

    • High density = higher competition, possibility for disease outbreak, possibility of depleting food source

  • Distribution: how individuals in a population are spaced out compared to each other

    • Random (trees)

    • Uniform (territorial animals)

    • Clumped (herd/group animals)

• Population Characteristics and Growth Factors

  • Sex ratio: ratio of males to females. Closer 50:50, the more ideal for breeding

    • Die-off or bottleneck effect can lead to skewed sex ratio (not enough females) limiting population growth.

  • Density-Dependent Factors: factors that influence population growth based on size.

  • Density-Independent Factors: factors that influence population growth independent of their size.

  • Food is a density dependent factor (also a limiting resource)

• Biotic Potential = max. potential growth rate, with no limiting resources

  • may occur initially, but limiting resources (competition, food, disease, predators) slow growth, and eventually limit population to carrying capacity (k)

  • Biotic potential = exponential growth

  • Logistic growth = initial rapid growth, then limiting factors limit population to K

• Population Size = (Immigrations + births) – (immigration + deaths)

3.6 Age Structure Diagrams

• Age Cohort and growth = groups of similarly aged individuals

  • 0-14 = prereproductive; 25-44 = reproductive age; 45+ = post reproductive

3.7 Total Fertility Rate (TFR)

• Total Fertility Rate (TFR): average number of children a woman in a population will bear through her lifetime.

  • Higher TFR = higher birth rate, higher population growth rate (generally)

• Replacement Level Fertility: the TFR is required to offset deaths in a population and keep population size stable.

• Infant Mortality Rate (IMR): number of deaths of children under 1 year per 1,000 people in a population

• Higher IMR = higher TFR, due to families having replacement children

• Factors in IMR decline –

  • Access to clean water

  • Access to healthcare

  • More reliable food supply

• Factors that Affect TFR

  • Development (affluence): more developed or wealthy nations have a lower TFR than less developed nations.

    • More educational access for women

    • More economic opportunity for women

    • Higher access to family planning education and contraceptives

    • Later age of first pregnancy

    • Less need for children to provide income through agricultural labor.

  • Government Policy: can play a huge role in fertility by coercive (forceful) or noncoercive (encouraging) policies.

    • Forced or voluntary sterilization

    • China’s 1 (now 2) child policy

    • Tax incentives to have fewer children.

    • Microcredits or loans to women without children to start business.

3.8 Human Population Dynamics

• Malthusian theory (what Malthus theorized)

  • Earth has a human carrying capacity, probably based on food production.

  • Human population growth is happening faster than growth of food production.

  • Humans will reach a carrying capacity limited by food.

• Technological Advancement

  • Humans can alter earth’s carrying capacity with technological innovation.

    • Synthetic fertilizer, gmo

• Birth Rate, Death Rate, and Growth

  • Growth rate (r­) = % increase in a population (usually per year)

  • Crude Birth Rate and Crude Death Rate (CBR & CDR)

    • Births and deaths per 1,000 people in a population

  • Calculating Growth Rate (r):

  • Rule of 70: the time it takes (in years) for a population to double is equal to 70 divided by the growth rate.

• Factors Affecting Human Population Growth

  • Factors that increase population growth

    • Higher TFR 🡪 higher birth rate

    • High infant mortality rate can drive up TFR (replacement children)

    • High immigration level

    • Increased access to clean water and healthcare (decrease death rate)

  • Factors that decrease population growth rate

    • High death rate

    • High infant mortality rate

    • Increased development (education and affluence)

    • Increased education for women

    • Delayed age of first child

    • Postponement of marriage age

• Standard of Living Indicators

  • Standard of Living: what quality of life is like for people of a country based.

  • Gross Domestic Product (GDP) = key economic indicator of standard of living

    • Total value of the goods and services produced.

    • Per capita GDP is total GDP/total population.

  • Life expectancy = key health indicator of standard of living

    • Average age a person will live to in a given country.

    • Increases with access to clean water, health care, stable food sources.

  • High GDP and life expectancy are both indicators of development and low population growth.

3.9 Demographic Transition

Unit 4 Earth Systems

Unit 5 Land and Water Use

5.1 Tragedy of the Commons (TOC)

• Tragedy of the commons: individuals will use shared/public resources in their own self-interest, degrading them.

  • Must be a public resource (not privately owned)

  • Must be degraded, overused, depleted, used-up in some way

  • Ex. Overgrazing, overfishing, water and air pollution, overuse of groundwater

• Externalities: negative cost associated with a human action, that aren’t accounted for in the price (unintended side-effects)

• How to solve:

  • Private land ownership

  • Fees or taxes for use

  • Taxes, fines, criminal charges for pollution or shared air/soil/water resources

5.2 Clearcutting

5.3 The Green Revolution

• The Green Revolution: shift in agriculture away from small, family operated farms to large, industrial-scale agribusiness

  • Increased use of mechanizations, GMOs, irrigation, fertilizers, and pesticides

  • Greatly increases efficiency of lands, short-term profitability, and food supply

  • Brings negative consequences (soil erosion, biodiversity loss, ground surface water contamination

• Mechanization

  • Increased use of tractors for plowing and tilling fields, and combines for harvesting = increased yields + profits

  • Increased reliance on fossil fuels (gasoline/diesel fuel)

    • Emits GHGs to atmosphere 🡪 climate change

  • Heavy machinery also compacts soil, decreasing H₂O holding capacity

    • Makes topsoil more prone to erosion

• GMOS: genetically modified crops have genes for drought tolerance, pest resistance, faster growth, and larger fruit/grain

  • Increases profitability with fewer plants lost to drought, disease, or pests + larger plant size + yield/acre

  • GMO crops are all genetically identical so genetic diversity is decreased and susceptibility to disease or pest is increased

• Irrigation: drawing water from the ground or nearby surface waters and distributing it on fields to increase plant growth

  • make agriculture possible in many parts of the world that are naturally to dry

  • can deplete groundwater sources, especially aquifers

  • over watering can drown roots ( no O₂ access) and causes soil salinization

• Pesticides: increase in use of synthetic pesticides – chemicals sprayed on crops that kill weeds, insects, rodents, another pests that eat or damage crops

  • Increase yield and profits with fewer plants lost to pests

  • Can wash off crops in runoff and kill or harm non-target species in local soils or waters

5.4 Impact of Agricultural Practices

• Monocropping: growing one single species (corn, wheat, soy) of crop

  • Highly efficient for harvest, pesticide and fertilizer application

  • Greatly decreases biodiversity (more prone to pests, fewer natural predators)

  • Increases soil erosion (crops harvested all at once and soil is left bare)

  • Decreases habitat diversity for species living in the area

• Tilling: mixing and breaking up soil to make planting easier (also loosens soil for roots)

  • Increases erosion by loosening topsoil, breaking up leftover root structure from harvest

  • Loss of organic matter and topsoil nutrients over time

  • Increased PM in air and sediments in nearby water (turbidity)

• Slash and Burn: cutting down vegetation and burning it to clear land for agriculture and return nutrients in plants to soil

  • Deforestation (loss of habitat, biodiversity)

  • Releases CO₂, CO, NO₂ – all lead to global warming

• Synthetic (inorganic) fertilizers

  • Don’t return organic matter to soil; no increased H₂O holding capacity and no soil decomposers

  • Leaching: water carries excess nutrients (nitrates and phosphates) into groundwater or into surface water (as runoff)

    • Contaminates groundwater for drinking

    • Causes eutrophication of surface waters

5.5 Irrigation

• Waterlogging: overwatering can saturate the soil, filling all soil pore space with water

  • Doesn’t allow air into pores, so roots can’t take in O₂ they need

  • Can stunt growth or kill crops

    • Solution: drip irrigation, or soil aeration

• Soil Salinization: the process of salt building up in soil overtime

  • Groundwater: used for irrigation naturally has small amounts of salt. Over time a toxic amount of soil can accumulate

    • Solution: drip irrigation, soil aeration, flushing with fresh water, switch to freshwater source

• Global Human water use

  • Industrial: power plants, metal/plastic manufacturing

  • Municipal: households (toilet, shower, drinking water)

  • Agriculture: water for livestock, irrigation water for crops

• Aquifers and Groundwater

  • Groundwater: water stored in pore space of permeable rock and sediment layers

  • Aquifers: useable groundwater deposits for humans

  • Replenished by groundwater recharge (rain water percolating down through soil into aquifer)

  • Confined aquifers recharge are longer-term water deposits that recharge more slowly

• Depletion of Aquifers

  • Saltwater intrusion: excessive pumping near coast lowers water table pressure, allowing saltwater to seep into groundwater

  • Cone of depression: forms when water table is lowered by excessive pumping, depleting water and drying nearby walls.

5.6 Pest Control Methods

• Pesticides: chemicals that are toxic to pests

  • Rodenticides – kill rodents

  • Fungicides – kill fungi

  • Insecticides – kill insects

  • Herbicides – kill plants

• Can cause pest to become resistant to pesticide with overuse – Pesticide treadmill

  • Genetic biodiversity gives some pest resistant traits to pesticide

  • Pesticide artificially selects for pest with resistance by killing all the non-resistant individuals, leaving only resistant ones

• GMOs (Genetic Modification): gene for pest resistant trait is added to the plant through genetic modification

  • Bt corn with bacteria gene that produces Bt crystals toxic to pests

  • Roundup Ready crops are GM to be resistant to broad herbicide (roundup) meaning roundup will kill weeds, but not crops

• Roundup ready crops have increased herbicide (glyphosate) use since crops can’t be harmed by it

• Bt corn has decreased insecticide use, since corn makes its own insecticide

• GM crops are all genetically identical (clones) so there is no genetic diversity in population

  • if there is a disease or pest that does affect the GM crops, they’re all vulnerable and there’s no chance of a genetic mutation providing an adaptive trait

5.7 Meat Production Methods

• CAFOS: also known as feedlots – densely crowded method where animals are fed grain (corn to raise them as quickly as possible)

  • Maximize land use and profit (most meat production per/unit of area)

  • Minimizes cost of meat for consumers

  • Given antibiotics and growth hormones to prevent disease outbreak and speed meat production

  • Animals produce large volumes of waste which can contaminate nearby surface or groundwater

  • Produces large amounts of CO₂, CH₄ (methane), and N₂O (greenhouse gasses → climate change)

• Manure Lagoons: large, open storage pits for animal waste

  • Waste contain ammonia, hormones, antibiotics, fecal coliform bacteria (e. coli)

  • Heavy rain can flood lagoons and contaminate nearby surface and ground water with runoff

  • Denitrification of ammonia in manure produces N₂0 (extremely powerful GFG)

  • Can be emptied and buried in landfills, or turned into fertilizer pellets.

• Free Range Grazing: animals (usually cows) graze on grass and grow at a natural rate without growth hormones

  • No need for antibiotics with dispersed population

  • Doesn’t require production of corn to feed animals

  • Waste is dispersed over land naturally, acting as fertilizer instead of building up in lagoons

  • Animals can graze on land to dry for most crop growth

  • Requires more total land use/pound of meat produced

    • Most expensive to consumer

• Overgrazing:

  • Too many animals grazing an area of land can remove all the vegetation (grass) which leads to topsoil erosion

  • Animals also compact soil, decreasing water holding capacity 🡪 more erosion

  • Desertification can occur if plants are killed by overgrazing and soil is compacted so much that it can’t hold enough water anymore

  • Rotational grazing (moving animals periodically) can prevent overgrazing

    • Can even increase growth of grass by distributing manure (natural fertilizer) and clipping grass back to size where growth is most rapid

• Inefficiency of meat: producing meat for humans to eat is far less efficient than producing plants in terms of energy, land and water use

  • Energy: all of the energy needed to plant, grow, harvest plants to feed animals

  • Land: all of the energy needs to grow plants to feed animals plus room animals take up

  • Water: all of the water for crops that animals eat plus the water the animals’ drink

5.8 Impacts of Overfishing

• Fisheries: population of fish used for commercial fishing

• Fishery collapse: when overfishing causes 90% population decline in a fishery

  • Population may never recover from fishery collapse due to decreased biodiversity, inability to find mates, and inbreeding depression

  • Decreases genetic biodiversity of fish populations and species biodiversity of ocean ecosystems if species are lost from ecosystem

  • Economic consequences: lost income for fishermen, lost tourism dollars for communities

• Bottom Trawling: especially harmful fishing method that involves dragging a large net along floor

  • Bycatch: unintended species like dolphins, whales, turtles caught in nets

  • Stirs up ocean sediment (turbidity) and destroys coral reef structure

• As we deplete large, predatory fisheries, we move down to smaller fish species

• Depletion of small fish populations limits fishery recovery and decreases food supply of marine mammals and seabirds

5.9 Mining

• Mining Basics

  • Ore: commercially valuable deposits of concentrated minerals that can be harvested and used as raw materials

  • Metals: elements that conduct electricity, heat, and have structural properties for building

  • Reserve: the known amount of a resource left that can be mined usually measured in years left of extraction

  • Overburden: soil, vegetation, and rocks that are removed to get to an ore deposit below

  • Tailing and slag: leftover waster material separated from the valuable metal or mineral within ore

• Surface mining

  • Removal of overburden to access ore near surface

  • Different types: open pit, strip, mountaintop removal, placer

  • Removal of vegetation and soil (topsoil erosion, habitat loss, increased stream turbidity)

  • As ore near surface becomes more scarce, mining moves deeper underground to subsurface mining

• Subsurface mining

  • More expensive due to higher insurance and health care costs for workers

  • Risks: poor ventilation leading to toxic gas exposure, mine shaft collapse, injury from falling rock, lung cancer, asbestos, fires, explosions

  • Vertical “shaft” drilled down into ground

• Environmental impacts of mining

  • Rainwater carries sulfuric acid into nearby streams, or infiltrates groundwater

  • Lowers pH of water, making toxic metals, like mercury and aluminum more soluble in water sources

  • Methane release: coal mining releases methane gas from rock around coal

  • PM release: coal mining especially, release lots of soot and other particulates that can irritate human and animal lungs

  • Acid mine drainage: rainwater leaks into abandoned mine tunnels and mixes with pyrite forming sulfuric acid

• Mine reclamation: process of restoring land to original state after mining has finished

5.10 Urbanization

• Urbanization: removing of vegetation to convert natural landscape to city (urban)

  • Replaces soil, vegetation, wetlands with impervious surfaces (concreate, asphalt, cement) which don’t allow water to infiltrate into the ground

  • CO₂ emissions

    • Cement production

    • Construction machinery

    • Deforestation (loss of future carbon sequestration + decomposition of cut trees)

    • Landfills needed for disposing trash from large population

  • Urbanization prevents groundwater recharge, causing precipitation to runoff into local bodies of water

• Urbanization in coastal cities

  • Population growth in coastal cities can lead to saltwater intrusion due to:

    • Excessive groundwater withdrawal near coast lowering water table pressure, allowing saltwater to seep into groundwater

    • Sea level rise due to warming of ocean (thermal expansion) and melting of ice caps (increasing ocean volume) can contaminate fresh groundwater with salt

• Suburbs: less dense areas surrounding urban areas

• Urban sprawl: population movement out of dense, urban centers to less dense suburban areas surrounding the city

  • Cheaper property in suburbs, cars making travel easy

• Urban sprawl causes expanded highways systems, increase in driving

• Solutions:

  • Urban growth boundaries: zoning laws set by cities preventing development beyond a certain boundary

  • Public transport and walkable city design that attract residents to stay

  • Mixed land use: residential, business, and entertainment buildings all located in the same are of a city

5.11 Ecological Footprint

• Ecological Footprint: measure of how much a person/group consumes, expressed in an area of land

  • Factors (land required for):

    • Food production

    • Raw materials (wood, metal, plastic)

    • Housing

    • Electricity production

      • Coal, natural gas, solar, wind, etc.

    • Disposing waste produced (landfill space)

• Ecological Footprint: measured in land (gha – global hectare) which is biologically productive hectare (2.47 acres)

• Carbon Footprint: measured in tonnes of CO₂ produced per year

  • all CO₂ released from an individual or groups consumption and activities

    • material goods

    • food production

    • energy use (gasoline, heat, electricity)

• ecological footprint can also be expressed in “number of earths” required if the entire world consumed same level of resources as a given induvial or group

5.12 Sustainability

• Sustainability: consuming a resource or using a space in a way that does not deplete or degrade it for future generations

• Maximum sustainable yield: the maximum amount of a renewable resource that can be harvested without reducing or depleting the resource for future use

• Environmental Indicators of Sustainability: factors that help us determine the health of the environment and guide us towards sustainable use of earth’s resources

• Biodiversity:

  • Genetics, species, and ecosystems

  • Higher biodiversity = healthier ecosystems

  • Declining biodiversity can indicate pollution, habitat destruction, climate change

  • Global extinction rate = strong environmental indicator since species extinction decreases species richness of earth

• Food Production

  • Indicates ability of earth’s soil, water, and climate to support agriculture

  • Major threats to food production = climate change, soil degradation (desertification, topsoil erosion), groundwater depletion

  • Increasing meat consumption = further strain on food production (takes away water and land from grain production)

  • Global grain production per capita has leveled off and shows signs of decline recently

• Atmospheric Temperature & CO₂

  • Life on earth depends on very narrow temperature range

  • CO₂ is GHG (traps infrared radiation and warms earth’s atmosphere)

    • Increased CO₂ = increased temperature

  • Deforestation (loss of CO₂ sequestration) and combustion of FF (emission of CO₂) increase atmosphere CO₂

  • Increasing CO₂ = unsustainable (dries out arable (farmable) land, destroys habitats, worsens storm intensity)

• Human Population and Resource Depletion

  • As human population grows, resource depletion grows

  • Resources are harvested unsustainably from natural ecosystems and degrade ecosystem health

    • More paper (lumber) = deforestation

    • More food = soil erosion, deforestation, groundwater depletion

    • More travel = fossil fuel mining = air, water, soil pollution, habitat destruction

5.13 Reducing Urban Runoff

• Environmental Consequences of Urban Runoff

  • Decreased infiltration (groundwater recharge)

  • Rain washes pollutants into storm drains and into local surface water

• Pollutants and effects

  • Salt (plant and insect death)

  • Sediment (turbidity)

  • Fertilizer (eutrophication)

  • Pesticides (kill non target species)

  • Oil and gasoline (suffocate fish/ kill aquaculture insects)

5.14 Integrated Pest Management (IPM)

• IPM Basics:

  • Using a variety of pest control methods that minimize environmental disruption and pesticide use

    • Researching and monitoring pests and targeting methods to specific pest life cycles

    • Biocontrol

    • Crop rotation

    • Intercropping

5.15 Sustainable Agriculture

• Soil Conservation: Agricultural techniques that minimize erosion

• Prevents loss of:

  • Nutrients in topsoil

  • Soil moisture

  • Decomposers in topsoil

  • Organic matter that traps soil moisture

• Improving Soil Fertility: methods of restoring nutrient levels in soil

  • Crop rotation: replanting same crops continuously depletes soil of the same nutrients

    • Crop rotation can allow soil to recover from nitrogen-demanding crops like corn

    • Peas/beans (legumes) have nitrogen fixing bacteria in their root nodules that can return nitrogen to the soil

  • Green Manure: green manure is leftover plant matter from a cover crop – a crop planted in the offseason, between harvest and replanting of main crop

    • Cover crop roots stabilize soil limiting topsoil erosion

    • Remains of cover crop (green manure) left on field breakdown to release nutrients into the soil

  • Limestone: releases calcium carbonate (base) which neutralizes acidic soil

    • Acidic soil has high H+ ion concertation, which displaces + charge nutrients from soil (leeching them out)

    • Acidic soil also makes toxic metals (aluminum) more soluble in soil

    • Calcium is needed plant nutrient as well

• Rotational Grazing: regular rotation of livestock to different pastures to prevent overgrazing

  • Overgrazing can kill plants, compact soil, and lead to erosion of topsoil

  • Rotational grazing can actually promote pasture growth at faster than normal rate

  • Clips grass back to length where growth is fastest and encourage deeper root growth

5.16 Aquaculture

• Aquaculture

  • Raising fish, or other aquatic species in cages/enclosures underwater

  • Benefits

    • Requires only small amount of water, space, and fuel

    • Reduce risk of fishery collapse (90% population decline in a fishery)

    • Doesn’t take up any land space (compared to beef, pork, chicken)

  • Drawbacks

    • High density produces high concentration of waste (e. Coli and eutrophication risks)

    • High density increases disease risk, which can be transmitted to wild population as well

    • May introduce non-native species or GMOs to local ecosystem if captive fish escape

    • Fish are fed antibiotics which can contaminate water via their waste

5.17 Sustainable Forestry

• Ecologically sustainable forestry

  • Forestry (using trees for lumber) that minimizes damage to ecosystem (habitat destruction, soil erosion, etc.)

  • Selective cutting or strip cutting

    • Only cutting some of the trees in an area (biggest and oldest) to preserve habitat (biodiversity) and topsoil

  • Using human and pack animal labor to minimize soil compaction from machinery

  • Replanting same species being logged

  • Maximizes long-term productivity of land and preserves forest for future generations

  • Using recycled wood or simply reusing without recycling

  • Wood can be chipped and used as mulch for gardens or agricultural fields

  • Reforestation: replanting of trees in areas that have been deforested

  • Selectively removing diseased trees to prevent spread of infection through entire forests

  • Fire suppression: the practice of putting out all natural forest fires as doon as they start

  • Prescribed burns: dead biomass is fuel for large forest fires, use of small controlled fires to burn dead biomass to prevent forest fires

Rate of consumption

• rate of use must be at or below rate of regeneration for renewables

• fossil fuels will run out because they take far long to regenerate than the rate we use them

6.2 Global Energy Consumption

Developed vs. Developing Countries

• developed nations use more energy on a per capital basis, but developed nations use more energy in total (higher population)

  • the average US resident uses 5x as much energy as the world average

  • developing nations are still industrializing and population is still growing rapidly

    • It will also increase on a per/person basis as their economies industrialize and residents achieve higher standards of living.

Fossil Fuels: Most Used Energy Source

• Fossil fuels are by far the most common fuel source globally

• Hydroelectric energy is the second largest source

• Nuclear Is the third largest source

Development Increase Fossil Fuel Consumption

• Many residents of less developed nations depend on subsistence fuels – biomass that they can easily gather/purchase

• Economic development 🡪 affluence (wealth) 🡪 higher per capita GDP 🡪 energy use

• As developing nations develop, fossil fuel consumption will increase

Factors that Affect Energy Source Use

• Availability: fossil fuel use depends on discovered reserves and accessibility of these reserves

• Price: fossil fuel prices fluctuate dramatically with discovery of new reserves or depletion of existing ones

  • Fracking open new natural gas reserves, increases availability, decreasing price, increasing use

• Government regulation: government can mandate certain energy source mixes

• Government cannot directly raise or lower prices of energy sources

• Government can use:

  • Tax increases to discourage companies from building fossil fuel power plants

  • Rebates or tax credits to encourage companies building renewable energy power plants

6.3 Fuel Types and Uses

Subsistence Fuels

• Biomass fuel sources that are easily accessible; often used in developing countries as a home heating or cooking fuel

• Wood (and charcoal) are two of the most common fuel sources in developing nations

  • Wood is free/cheap to cut down and utilize as fuel; can cause deforestation and habitat loss

  • Charcoal is made by heating wood under low oxygen conditions for a long time

• Peat is partially decomposed organic matter found in wet, acidic ecosystems like bogs and moors

  • Can be dried and used as a biomass fuel source

Coal Formation

• Pressure from overlying rock and sediment layers compacts peat into coal over time

• In order of energy density and quality: lignite 🡪 bituminous 🡪 anthracite

• The deep a coal reserve is buried, the more pressure from overlying rock layers and the more energy dense

• Because higher energy density means more energy released when a fuel source is burned, anthracite is the most valuable form of coal (highest quality)

Natural Gas

• Decaying remains of plants and animals (mostly marine life) are buried under layers of rock and converted by pressure into oil (petroleum) and natural gas over time

• Natural gas is mostly methane and is found on top of trapped oil (petroleum) deposits

• Forms when oil is trapped in a porous, sedimentary rock, underneath a harder impermeable rock layer that doesn’t let the gas escape

• Considered the cleanest fossil fuel (produces the fewest air pollutants and least CO₂ when burned)

Crude Oil (petroleum)

• Decaying organic matter trapped under rock layers is compressed into oil over time

• Extracted by drilling a well through the overlying rock layers to reach the underground deposit and then pumping liquid oil out under pressure

• Can also be recovered from tar sands (combination of clay, sand, water, and bitumen)

  • Bitumen Is a thick, sticky, semi-solid form of petroleum (not liquid)

  • Extracting and using oil from tar sands is extremely energy and water intensive

Fossil Fuel Products

• Crude oil (petroleum) is converted into lots of different products through the process of fractional distillation

• Crude oil is burned in a furnace and vapor passes into a column where different hydrocarbons are based on their boiling points

6.4 Distribution of Natural Energy Resources

Fracking and Shale Gas

• Hydraulic fracturing (fracking) is a method of natural gas extraction that has extended access to natural gas

  • Gas trapped in semi-permeable, sedimentary rock layers, such as shale, is released by cracking the rock with pressurized water

  • Fracking natural gas from shale rock increase and extends supply of natural gas

Shale Gas Reserves

• Fossil fuels are non-renewable, and will eventually be depleted, but short-term economic profit still drives extraction and use

Tar/Oil Sands

• Tar or oil sands are bitumen deposits where crude oil can be recovered, but with higher water and energy inputs

• Canada (Alberta region) = world’s largest oil sands reserve

6.5 Distribution of Natural Energy Resources

Fossil Fuel Combustion

• Reaction between oxygen and fossil fuels that release energy as heat and produces CO₂ and H₂O as products

• Methane, gasoline, propane, butane, and coal are al fossil fuels (hydrocarbons) that release energy in the same way

Fossil Fuels to Generate Electricity

• The #1 source of electricity production globally is coal, followed by natural gas

• These steps of electricity generation are the same, no matter what you’re burning to produce the initial heat

Heat 🡪 water into steam 🡪 steam turns a turbine 🡪 turbine powers generator 🡪 generator produces electricity

• Coal, oil, natural gas, biomass, and trash can all be burned to drive this same process and create energy

Environmental Consequences: Coal

• Habitat destruction to clear land for mining

• Produces pollutants and releases CO₂ (GHG 🡪 global warming)

  • Release more CO₂ than any other fossil fuel when burned for electricity generation

  • Releases soot and ash, which can irritate respiratory tracts

  • Produces toxic ash contaminate with lead, mercury, and arsenic

Generating Electricity

• Coal is ~30% efficient as a fuel source for generating electricity (30% of energy from the bonds in the hydrocarbons are converted to electricity)

• Much of the energy “lost” or not converted into electricity escapes as heat

• Cogeneration: when the heat produced from electricity generation is used to provide heat (air and hot water) to a building

  • CHP (combined heat and power) systems are close to 90% efficient (much better than coal/NG alone)

Oil/Petroleum Extraction

• Extracted by drilling a well through the overlying rock layers to reach the underground deposit and then pumping liquid oil out under pressure

• Can also be recovered from tar sands (combination of clay, sand, water, and bitumen)

  • Bitumen is a thick, sticky, semi-solid form of petroleum (noy liquid)

  • Extracting and using oil from tar sands is extremely energy and water intensive

Environmental Consequences

• Tar Sands

  • Habitat destruction to clear land for: roads, drilling equipment, digging through ground surface to reach deposits

  • Ground or nearby surface water depletion (H₂O needed for steam and for washing impurities from bitumen at refinery)

• Crude Oil/ Petroleum

  • Possibility of spill (either from tanker ships or pipelines breaking

  • Habitat loss or fragmentation when land is cleared for roads, drilling equipment, pipelines

• Fracking

  • Possibility of well leaking and contaminating groundwater with fracking fluid (salt, detergents, acids) or hydrocarbons

    • Ponds can overflow or leach into ground and contaminate surface or ground waters with fracking fluid (salt, detergents, acids)

  • Depletion of ground or surfaces waters nearby (as they’re drawn from for fracking fluid)

Fracking (Hydraulic fracturing)

• Used to extract natural gas from sedimentary rock

• Vertical well is drilled down to sedimentary rock layer, then turns horizontally into the rock layer

  • Perforating gun cracks (fractures) the rock layer around horizontal well, making it more permeable

  • Fracking fluid (water, salt, detergents, acids) is pumped into well at very high pressure to crack the rock even more and allow natural gas to flow out

  • Flowback water: (used fracking fluid) flows back out well and is collected and stored in containers or ponds nearby

6.6 Nuclear Energy

Nuclear Fission and Radioactivity

• A neutron is fired into the nucleus of a radioactive (unstable) element, such as uranium

  • Nucleus breaks apart and releases lots of energy (heat) + more neutrons that break more nuclei apart, releasing more energy (chain reaction)

• Radioactivity refers to the energy given off by the nucleus of a radioactive isotope (uranium-235)

  • Radioactive nuclei decay, or breakdown and give off energy (radiation) even without fission; nuclear fission just releases tons of energy all at once

  • Radioactive Half-life = the amount of time it takes for 50% of a radioactive substance to decay

Generating Electricity

• Same electricity generation process as with FFs, just uranium fission to heat water in steam

  • Heat 🡪 water into steam 🡪 steam turns turbine 🡪 turbine powers generator 🡪 generator produces electricity

• U-235 stored in fuel rods, submerged in water in reaction core; heat from fission turns H₂0 🡪 steam

  • Control rods are lowered into reactor core to absorb neutrons and slow down the reaction, preventing meltdown (explosion)

  • Water pump brings in cool water to be turned into steam and also cools reactor down from overheating

  • Cooling tower allows steam from turbine to condense back into liquid and cool down before being reused

Nonrenewable but cleaner than FFs

• Nuclear energy is NONRENWABLE because radioactive elements like Uranium are limited

• Other drawbacks of nuclear energy include possibility of meltdown and radioactive contaminations

  • Spent fuel rods: used fuel rods remain radioactive for millions of years and need to be stored in lead containers on site at nuclear power plants

  • Mine tailings: leftover rock and soil from mining may have radioactive elements that can contaminate water or soil nearby

  • Water use: nuclear powerplants require lots of water and can deplete local surface or groundwater sources

  • Thermal pollution: hot water from power plants released back into surface waters can cause thermal shock

Nuclear Meltdowns

• Three Mile Island (US): partial meltdown due to testing error; radiation released but no deaths or residual cancer cases

• Fukushima (Japan): an earthquake and tsunami triggered cooling pump failure that lead to meltdown (explosion of reactor core) and widespread radiation release

• Chernobyl (Ukraine): stuck cooling valve during test lead to complete meltdown (explosion of reactor core), several deaths and widespread radiation release

• Environmental consequences of meltdowns: genetic mutations and cancer in surrounding people, animals and plants due to radiation released from reactor core

• Contaminated soil: radiation can remain in soil and harm plants and animals in the future

• Radiation spread: radiation can be carried by the wind over long distances; affecting ecosystems far from the meltdown site

6.7 Energy From Biomass

Biomass vs Biofuels

• Biomass: organic matter (wood/charcoal, dried animal waste, dead leaves/brush) burned to release heat – primarily for heating homes/cooking

  • Utilized primarily in developing world for heating homes and cooking food

    • Easy to harvest, available, cheap/free (subsistence fuel)

  • Can also be burned in powerplants to generate electricity (less common than fossil fuels)

• Biofuels: liquid fuels (ethanol, biodiesel) created from biomass (corn, sugar cane, palm oil)

  • Used as replacement fuel sources for gasoline, primarily in vehicles

Modern vs. Fossil Carbon

• Biomass burning releases CO₂, but doesn’t increase atmospheric CO₂ levels like fossil fuel burning does

  • Burning biomass releases modern carbon whereas fossil fuel burning releases fossil carbon that had been stored for millions of years

Human Health and Environmental Consequences of Biomass Burning

• Biomass burning release CO, NO, OM, and VOCs – as respiratory irritants

• Environmental consequences = deforestation and air pollutants

Biofuels: Ethanol and Algae

• Corn and sugar cane are fermented into ethanol which is mixed with gasoline

• Environmental consequences = all the negative consequences of monocrop agriculture

Biodiesel

• Liquid fuels produced specifically from plant oils (soy, canola, palm)

6.8 Solar Energy

Active vs. Passive Solar Energy

• Passive solar: absorbing or blocking heat from the sun, without use of mechanical/electrical equipment

• Active Solar: use of mechanical/electrical equipment to capture sun’s heat (solar water heaters or CST – concentrated solar thermal), or convert light rays directly into electricity (PV cells)

Photovoltaic Cells (PV)

• solar panels contain semiconductor that emit low voltage electrical currents when exposed to sun

  • photons (particles carrying energy from sun) cause separation of charges between two semiconductor layers; electrons separate from protons and flow through circuit to load, delivering energy (as electricity)

  • PV cells on a roof can directly power the building, or send excess electricity back to the grid for other users (earning you a credit from your utility company)

• a drawback is intermittency (solar energy can only be generated during the day)

Concentrated Solar Thermal (CST)

• heliostats (mirrors) reflect sun’s rays onto a central water tower in order to heat water to produce steam to turn a turbine 🡪 electricity

• a drawback is habitat destruction and light beams frying birds in mid air

Community (solar farm) vs. rooftop solar

• large scale solar “farms” can generate lots of electricity, but do take up land and cause habitat loss/fragmentation

• rooftop solar doesn’t take up land, but only produces a little electricity

Solar Energy Pros

• no air pollutants released to generate electricity

• no CO₂ released when generated electricity

• renewable, unlike fossil fuels which will run out

• no mining of fossil fuels for electricity production

Solar Energy Cons

• semiconductor metals (silicon) still need to be mined to produce PV cells (solar panels)

• this can disrupt habitats and pollute water with mine tailings, air with particulate matter

• silicon is a limited resource

• solar panel farms can displace habitats

6.9 Hydroelectricity

Hydroelectricity Basics

• kinetic energy of moving water 🡪 spins a turbine (mechanical energy) 🡪 turbine powers generator

  • water moves either with natural current of river or tides, or by falling vertically through channel in a dam

  • by far the largest renewable source of electricity globally

  • China, Brazil, and US = 3 biggest hydroelectricity producers

Water Impoundment (DAMS)

• Dam built in a river creates a large artificial lake behind the dam (reservoir)

• Damming the river enables operators to allow more or less water through the channel in the dam, increasing or decreasing electricity production (water flows through channel 🡪 turns turbine 🡪 turbine powers generator 🡪 electricity)

• Also allows for control of flow downstream, prevention of seasonal flooding due to high rainfall

• Reservoirs are also a source of recreation money

• 2 big impacts = flooding of ecosystems behind dam and sedimentation (buildup of sediments behind dam)

Run of River System and Tidal Energy

• a dam diverts the natural current of a river through man-made channel beside the river

• natural current of the river turns the turbine 🡪 powers the generator 🡪 electricity

• less impactful to surrounding ecosystem since no reservoir is formed and ecosystems behind dam aren’t flooded

• doesn’t stop natural flow of sediments downstream like water impoundment systems do

• doesn’t generate nearly as much power and may be unavailable in warmer seasons when river water levels are lower

• Tidal power: comes from tidal ocean flow turning turbine (coastal areas only)

Drawbacks of Hydroelectricity Dams (Ecological/ Environmental/ Economic)

• Reservoir floods habitats behind dam (forests/wetlands 🡪 gone; river becomes a lake)

  • Sedimentation changes upstream and downstream conditions

    • Upstream becomes warmer (less CO₂) and rocky streambed habitats covered in sediment

    • Downstream loses sediment (important nutrient source), decreased water level, loses streambed habitat

  • Downstream wetlands especially suffer since nutrients in sediment doesn’t reach them

• Fossil fuel combustion during dam constriction, increased evaporation due to larger surface area in reservoir, and methane release due to anaerobic decomposition of organic matter in reservoir

• Human homes and business must be relocated due to reservoir flooding, initial construction is very expensive (does create long-term jobs though), sediment buildup must be dredged (removed by crane) eventually

  • Loss of ecosystem services from downstream wetlands, potential loss of fishing revenue if salmon breeding is disrupted

Fish Ladders

• Cement “steps” or series of pools that migratory fish like salmon can use to continue migration upstream, around or over dams

  • Enables continued breeding for salmon, food source for predators like large birds, bears, and fishing revenue for humans

  • “salmon cannon” is a similar alternative that enables salmon to be captured or directed into a tube that carries them over the dam

Benefits of Hydroelectric Dams

• No GHG emissions when producing electricity (initial construction does require cement and machines that emit GHGs)

  • Reservoir and dam can be tourist attractions

  • Jobs are created to maintain the dam

  • Reliable electricity source generated for surrounding area

  • No air pollutants released during electricity generation

• Allows for control of downstream seasonal flooding

6.10 Geothermal Energy

Geothermal Basics

• Natural radioactive decay of elements deep in earth’s core gives off heat, driving magma convection currents which carry heat to upper portion of mantle, close to earth’s surface

  • Water can be piped down into the ground and heated by this heat from the mantle

  • Hot water can be converted into steam 🡪 turbine 🡪 electricity can be used to heat homes directly

• Geothermal for electricity: naturally heated water reservoirs underground are drilled into and piped up to the surface (or water can be piped down into naturally heated rock layers)

  • The heat from magma turns the water into steam, which is forced through pipes to spin a turbine

  • Water is cooled in cooling tower and returned to the ground to start the process over

  • Renewable since heat from earth’s core won’t run out; but only if groundwater is returned after use

Ground Source Heat Pump

• Often referred to as “geothermal” but technically the heat does not come from geologic activity (comes from the ground storing heat from the sun)

  • More accurate name is “ground source heat pump”

  • 10 feet down, the ground stays a consistent 50-60 degrees due to holding heat from sun (not warmed by geothermal energy from magma – so not technically geothermal energy)

  • Heat absorbing fluid is pumped through a pipe into the ground where it either takes on heat from the ground, or gives off heat to the ground

Geothermal Heating

• True geothermal heating involves piping water deep into ground to be heated by magma and then transferring heat from water to the building

  • Different than ground source heat pump

  • Well must go thousands of meters (kms) down into the ground to reach heated water reservoir

  • Heated water is piped up to surface and sent to homes or business to heat them

Geothermal pros

• Potentially renewable, only if water is piped back into the ground for reuse

• Much less CO₂ emission than fossil fuel electricity

Geothermal Cons

• Not everywhere on earth has access to geothermal energy reaching close enough to surface to access it

• Hydrogen sulfide can be released, which is toxic and can be lethal to humans and animals

• Cost of drilling that deep in the earth can be very high initially

6.11 Hydrogen Fuel Cell

Hydrogen Fuel Cell Basics

• Use hydrogen as a renewable, alternative fuel source to fossil fuels

  • H₂ gas and O₂ are the inputs used to generate electricity; H₂O is given off as a waste product

• H₂ gas enters fuel cell where it’s split into protons and electrons by an electrolyte membrane that only lets protons pass through

  • Electrons take an alternative route (circuit) around the membrane, which generates an electrical current

  • O₂ molecules enter fuel cell break apart into individual O atoms and combine with two hydrogens to form H₂O as a by product

• Most common application is in vehicles

  • Replaces gasoline (non-renewable, GHG releasing and air pollution) with H fuel (no air pollutants released and only H₂O vapor)

Creating H₂ Gas

• key challenge to H fuel cells is obtaining pure H gas (because it doesn’t exist by itself as a gas naturally)

  • separating H₂ gas from other molecules like H₂O or CH₄ is very energy intensive

    • two main processes are steam reforming (95% of all H production) and electrolysis (less common, but more sustainable

  • stream reforming: burning natural gas (CH₄) and suing steam to separate the H gas from the methane (CH₄)

    • emits CO₂ and requires natural gas input

  • electrolysis: electrical current is applied to water, breaking it into O₂ and H₂

    • no CO₂ emission, but does require electricity

Hydrogen as an Energy Carrier (pros)

• because H₂ gas can be stored in pressurized tanks, it can be transported for use creating electricity later, in a different location

• can also be used as a fuel for vehicles (replacing gasoline) or to create ammonia for fertilizer, or in the chemical industry

Drawbacks of Hydrogen Fuel Cells

• since 95% of H₂ production requires methane (CH₄), H fuel cells are based on a non-renewable and CO₂ releasing energy source

  • if electrolysis is used, it’s only as sustainable as the electricity source

  • widespread H fuel cell use would require building widespread H distribution network (similar to current system for gasoline)

  • H fuel stored in gas form in vehicles would require much larger tanks than current gasoline tanks

6.12 Wind Energy

Wind Turbine Electricity Generation

• Kinetic energy of moving air (wind) spins a turbine; generator converts mechanical energy of turbine into electricity

• Blades of turbine are connected to gearbox by a shaft that rotates; rotating gears create mechanical energy that the generator transforms into electricity

  • Average turbine can power 460 homes

  • Motorized drive within shaft can turn the turbine to face wind

Wind Turbine Location

• Clustered in groups (wind projects or farms) in flat, open areas (usually rural)

  • Location them together makes service, repair, and building transmission lines to them easier

    • Can share land with agricultural use

• Offshore wind = wind farms in oceans or lakes

  • Capitalizes on faster wind speeds

  • Does require transmission lines bult across long distances to reach land though

Wind Energy Benefits and Drawbacks

6.13 Energy Conservation

Small Scale vs. Large Scale Energy Conservation

Sustainable Home Designs

• Ways to either block out or take advantages of sun’s natural heat, or keep in heating/cooling to decrease energy required

  • Deciduous shade trees for landscaping (leaves block sun in summer, but allow it in during winter)

  • Using passive solar design concepts to trap sun’s heat and decrease energy from heating system (heat absorbing walls, triple or double paned windows)

  • Well-insulated walls/attic to trap heat in winter and cool air from AC system in summer

  • This decreases electricity used by AC unit and energy used by heating system

Water Conservation

• Native plants require less watering than traditional lawns (also increase biodiversity of pollinators and require less fertilizer)

• Low-flow shoers, toilets, and dishwashers do the same job with less total water (less energy to purify and pump to homes)

• Rain barrels allow rain water to be used for watering plants or washing cars

Energy Conservation – Transportation

• ~28% of total US energy use comes from transport of goods and people

• Improving fuel economy of US fleet of vehicles conserves energy as less gasoline/diesel is needed to travel same distance

  • CAFE (Corporate Average Fuel Economy) standards are regulations set in US to require auto manufacturers to make cars that meet certain MPG standards, or pay penalties

• Hybrids have both a gasoline and electric engine, enabling them to have higher MPG ratings

  • Breaking system charges the electric battery, which powers electric motor

  • Electric vehicles (EVs or BEVs) use no gasoline, but still require electricity (only as sustainable as electricity source)

  • Public transit and carpooling are even better energy-saving transport options

Sustainable Building Design

• Decreasing the amount of energy required to build larger buildings and heat/cool them

  • Green roof or walls can decrease runoff, and absorb sun’s heat, decreasing energy needed for cooling building and surrounding area (lessens heat island effect)

  • Sun lights on rood, or windows on sides can decrease electricity used for lighting

  • Recycled materials can reduce energy required to produce new ones (glass, wood, even fly ash from coal can be used in foundation)

Managing Peak Demand and Smart Grid Technology

• Peak demand is the time of day or year (often early night time hours or very hot weather events) that electricity demand is highest

  • If demand exceeds supply, rolling blackouts occur

  • To manage peak demand, some utilities use a variable price model for electricity

    • Users pay a higher rate during peak demand hours or events, to discourage use

    • Users pay a lower rate/kWh when using a lower amount of energy (incentivizes lower overall use)

• “smart grid” is just the idea of managing demand and energy sources in a more varied way

Unit 6 Energy

6.1 Renewable vs. Nonrenewable Energy Sources

Rate of consumption

• rate of use must be at or below rate of regeneration for renewables

• fossil fuels will run out because they take far long to regenerate than the rate we use them

6.2 Global Energy Consumption

Developed vs. Developing Countries

• developed nations use more energy on a per capital basis, but developed nations use more energy in total (higher population)

  • the average US resident uses 5x as much energy as the world average

  • developing nations are still industrializing and population is still growing rapidly

    • It will also increase on a per/person basis as their economies industrialize and residents achieve higher standards of living.

Fossil Fuels: Most Used Energy Source

• Fossil fuels are by far the most common fuel source globally

• Hydroelectric energy is the second largest source

• Nuclear Is the third largest source

Development Increase Fossil Fuel Consumption

• Many residents of less developed nations depend on subsistence fuels – biomass that they can easily gather/purchase

• Economic development 🡪 affluence (wealth) 🡪 higher per capita GDP 🡪 energy use

• As developing nations develop, fossil fuel consumption will increase

Factors that Affect Energy Source Use

• Availability: fossil fuel use depends on discovered reserves and accessibility of these reserves

• Price: fossil fuel prices fluctuate dramatically with discovery of new reserves or depletion of existing ones

  • Fracking open new natural gas reserves, increases availability, decreasing price, increasing use

• Government regulation: government can mandate certain energy source mixes

• Government cannot directly raise or lower prices of energy sources

• Government can use:

  • Tax increases to discourage companies from building fossil fuel power plants

  • Rebates or tax credits to encourage companies building renewable energy power plants

6.3 Fuel Types and Uses

Subsistence Fuels

• Biomass fuel sources that are easily accessible; often used in developing countries as a home heating or cooking fuel

• Wood (and charcoal) are two of the most common fuel sources in developing nations

  • Wood is free/cheap to cut down and utilize as fuel; can cause deforestation and habitat loss

  • Charcoal is made by heating wood under low oxygen conditions for a long time

• Peat is partially decomposed organic matter found in wet, acidic ecosystems like bogs and moors

  • Can be dried and used as a biomass fuel source

Coal Formation

• Pressure from overlying rock and sediment layers compacts peat into coal over time

• In order of energy density and quality: lignite 🡪 bituminous 🡪 anthracite

• The deep a coal reserve is buried, the more pressure from overlying rock layers and the more energy dense

• Because higher energy density means more energy released when a fuel source is burned, anthracite is the most valuable form of coal (highest quality)

Natural Gas

• Decaying remains of plants and animals (mostly marine life) are buried under layers of rock and converted by pressure into oil (petroleum) and natural gas over time

• Natural gas is mostly methane and is found on top of trapped oil (petroleum) deposits

• Forms when oil is trapped in a porous, sedimentary rock, underneath a harder impermeable rock layer that doesn’t let the gas escape

• Considered the cleanest fossil fuel (produces the fewest air pollutants and least CO₂ when burned)

Crude Oil (petroleum)

• Decaying organic matter trapped under rock layers is compressed into oil over time

• Extracted by drilling a well through the overlying rock layers to reach the underground deposit and then pumping liquid oil out under pressure

• Can also be recovered from tar sands (combination of clay, sand, water, and bitumen)

  • Bitumen Is a thick, sticky, semi-solid form of petroleum (not liquid)

  • Extracting and using oil from tar sands is extremely energy and water intensive

Fossil Fuel Products

• Crude oil (petroleum) is converted into lots of different products through the process of fractional distillation

• Crude oil is burned in a furnace and vapor passes into a column where different hydrocarbons are based on their boiling points

6.4 Distribution of Natural Energy Resources

Fracking and Shale Gas

• Hydraulic fracturing (fracking) is a method of natural gas extraction that has extended access to natural gas

  • Gas trapped in semi-permeable, sedimentary rock layers, such as shale, is released by cracking the rock with pressurized water

  • Fracking natural gas from shale rock increase and extends supply of natural gas

Shale Gas Reserves

• Fossil fuels are non-renewable, and will eventually be depleted, but short-term economic profit still drives extraction and use

Tar/Oil Sands

• Tar or oil sands are bitumen deposits where crude oil can be recovered, but with higher water and energy inputs

• Canada (Alberta region) = world’s largest oil sands reserve

6.5 Distribution of Natural Energy Resources

Fossil Fuel Combustion

• Reaction between oxygen and fossil fuels that release energy as heat and produces CO₂ and H₂O as products

• Methane, gasoline, propane, butane, and coal are al fossil fuels (hydrocarbons) that release energy in the same way

Fossil Fuels to Generate Electricity

• The #1 source of electricity production globally is coal, followed by natural gas

• These steps of electricity generation are the same, no matter what you’re burning to produce the initial heat

Heat 🡪 water into steam 🡪 steam turns a turbine 🡪 turbine powers generator 🡪 generator produces electricity

• Coal, oil, natural gas, biomass, and trash can all be burned to drive this same process and create energy

Environmental Consequences: Coal

• Habitat destruction to clear land for mining

• Produces pollutants and releases CO₂ (GHG 🡪 global warming)

  • Release more CO₂ than any other fossil fuel when burned for electricity generation

  • Releases soot and ash, which can irritate respiratory tracts

  • Produces toxic ash contaminate with lead, mercury, and arsenic

Generating Electricity

• Coal is ~30% efficient as a fuel source for generating electricity (30% of energy from the bonds in the hydrocarbons are converted to electricity)

• Much of the energy “lost” or not converted into electricity escapes as heat

• Cogeneration: when the heat produced from electricity generation is used to provide heat (air and hot water) to a building

  • CHP (combined heat and power) systems are close to 90% efficient (much better than coal/NG alone)

Oil/Petroleum Extraction

• Extracted by drilling a well through the overlying rock layers to reach the underground deposit and then pumping liquid oil out under pressure

• Can also be recovered from tar sands (combination of clay, sand, water, and bitumen)

  • Bitumen is a thick, sticky, semi-solid form of petroleum (noy liquid)

  • Extracting and using oil from tar sands is extremely energy and water intensive

Environmental Consequences

• Tar Sands

  • Habitat destruction to clear land for: roads, drilling equipment, digging through ground surface to reach deposits

  • Ground or nearby surface water depletion (H₂O needed for steam and for washing impurities from bitumen at refinery)

• Crude Oil/ Petroleum

  • Possibility of spill (either from tanker ships or pipelines breaking

  • Habitat loss or fragmentation when land is cleared for roads, drilling equipment, pipelines

• Fracking

  • Possibility of well leaking and contaminating groundwater with fracking fluid (salt, detergents, acids) or hydrocarbons

    • Ponds can overflow or leach into ground and contaminate surface or ground waters with fracking fluid (salt, detergents, acids)

  • Depletion of ground or surfaces waters nearby (as they’re drawn from for fracking fluid)

Fracking (Hydraulic fracturing)

• Used to extract natural gas from sedimentary rock

• Vertical well is drilled down to sedimentary rock layer, then turns horizontally into the rock layer

  • Perforating gun cracks (fractures) the rock layer around horizontal well, making it more permeable

  • Fracking fluid (water, salt, detergents, acids) is pumped into well at very high pressure to crack the rock even more and allow natural gas to flow out

  • Flowback water: (used fracking fluid) flows back out well and is collected and stored in containers or ponds nearby

6.6 Nuclear Energy

Nuclear Fission and Radioactivity

• A neutron is fired into the nucleus of a radioactive (unstable) element, such as uranium

  • Nucleus breaks apart and releases lots of energy (heat) + more neutrons that break more nuclei apart, releasing more energy (chain reaction)

• Radioactivity refers to the energy given off by the nucleus of a radioactive isotope (uranium-235)

  • Radioactive nuclei decay, or breakdown and give off energy (radiation) even without fission; nuclear fission just releases tons of energy all at once

  • Radioactive Half-life = the amount of time it takes for 50% of a radioactive substance to decay

Generating Electricity

• Same electricity generation process as with FFs, just uranium fission to heat water in steam

  • Heat 🡪 water into steam 🡪 steam turns turbine 🡪 turbine powers generator 🡪 generator produces electricity

• U-235 stored in fuel rods, submerged in water in reaction core; heat from fission turns H₂0 🡪 steam

  • Control rods are lowered into reactor core to absorb neutrons and slow down the reaction, preventing meltdown (explosion)

  • Water pump brings in cool water to be turned into steam and also cools reactor down from overheating

  • Cooling tower allows steam from turbine to condense back into liquid and cool down before being reused

Nonrenewable but cleaner than FFs

• Nuclear energy is NONRENWABLE because radioactive elements like Uranium are limited

• Other drawbacks of nuclear energy include possibility of meltdown and radioactive contaminations

  • Spent fuel rods: used fuel rods remain radioactive for millions of years and need to be stored in lead containers on site at nuclear power plants

  • Mine tailings: leftover rock and soil from mining may have radioactive elements that can contaminate water or soil nearby

  • Water use: nuclear powerplants require lots of water and can deplete local surface or groundwater sources

  • Thermal pollution: hot water from power plants released back into surface waters can cause thermal shock

Nuclear Meltdowns

• Three Mile Island (US): partial meltdown due to testing error; radiation released but no deaths or residual cancer cases

• Fukushima (Japan): an earthquake and tsunami triggered cooling pump failure that lead to meltdown (explosion of reactor core) and widespread radiation release

• Chernobyl (Ukraine): stuck cooling valve during test lead to complete meltdown (explosion of reactor core), several deaths and widespread radiation release

• Environmental consequences of meltdowns: genetic mutations and cancer in surrounding people, animals and plants due to radiation released from reactor core

• Contaminated soil: radiation can remain in soil and harm plants and animals in the future

• Radiation spread: radiation can be carried by the wind over long distances; affecting ecosystems far from the meltdown site

6.7 Energy From Biomass

Biomass vs Biofuels

• Biomass: organic matter (wood/charcoal, dried animal waste, dead leaves/brush) burned to release heat – primarily for heating homes/cooking

  • Utilized primarily in developing world for heating homes and cooking food

    • Easy to harvest, available, cheap/free (subsistence fuel)

  • Can also be burned in powerplants to generate electricity (less common than fossil fuels)

• Biofuels: liquid fuels (ethanol, biodiesel) created from biomass (corn, sugar cane, palm oil)

  • Used as replacement fuel sources for gasoline, primarily in vehicles

Modern vs. Fossil Carbon

• Biomass burning releases CO₂, but doesn’t increase atmospheric CO₂ levels like fossil fuel burning does

  • Burning biomass releases modern carbon whereas fossil fuel burning releases fossil carbon that had been stored for millions of years

Human Health and Environmental Consequences of Biomass Burning

• Biomass burning release CO, NO, OM, and VOCs – as respiratory irritants

• Environmental consequences = deforestation and air pollutants

Biofuels: Ethanol and Algae

• Corn and sugar cane are fermented into ethanol which is mixed with gasoline

• Environmental consequences = all the negative consequences of monocrop agriculture

Biodiesel

• Liquid fuels produced specifically from plant oils (soy, canola, palm)

6.8 Solar Energy

Active vs. Passive Solar Energy

• Passive solar: absorbing or blocking heat from the sun, without use of mechanical/electrical equipment

• Active Solar: use of mechanical/electrical equipment to capture sun’s heat (solar water heaters or CST – concentrated solar thermal), or convert light rays directly into electricity (PV cells)

Photovoltaic Cells (PV)

• solar panels contain semiconductor that emit low voltage electrical currents when exposed to sun

  • photons (particles carrying energy from sun) cause separation of charges between two semiconductor layers; electrons separate from protons and flow through circuit to load, delivering energy (as electricity)

  • PV cells on a roof can directly power the building, or send excess electricity back to the grid for other users (earning you a credit from your utility company)

• a drawback is intermittency (solar energy can only be generated during the day)

Concentrated Solar Thermal (CST)

• heliostats (mirrors) reflect sun’s rays onto a central water tower in order to heat water to produce steam to turn a turbine 🡪 electricity

• a drawback is habitat destruction and light beams frying birds in mid air

Community (solar farm) vs. rooftop solar

• large scale solar “farms” can generate lots of electricity, but do take up land and cause habitat loss/fragmentation

• rooftop solar doesn’t take up land, but only produces a little electricity

Solar Energy Pros

• no air pollutants released to generate electricity

• no CO₂ released when generated electricity

• renewable, unlike fossil fuels which will run out

• no mining of fossil fuels for electricity production

Solar Energy Cons

• semiconductor metals (silicon) still need to be mined to produce PV cells (solar panels)

• this can disrupt habitats and pollute water with mine tailings, air with particulate matter

• silicon is a limited resource

• solar panel farms can displace habitats

6.9 Hydroelectricity

Hydroelectricity Basics

• kinetic energy of moving water 🡪 spins a turbine (mechanical energy) 🡪 turbine powers generator

  • water moves either with natural current of river or tides, or by falling vertically through channel in a dam

  • by far the largest renewable source of electricity globally

  • China, Brazil, and US = 3 biggest hydroelectricity producers

Water Impoundment (DAMS)

• Dam built in a river creates a large artificial lake behind the dam (reservoir)

• Damming the river enables operators to allow more or less water through the channel in the dam, increasing or decreasing electricity production (water flows through channel 🡪 turns turbine 🡪 turbine powers generator 🡪 electricity)

• Also allows for control of flow downstream, prevention of seasonal flooding due to high rainfall

• Reservoirs are also a source of recreation money

• 2 big impacts = flooding of ecosystems behind dam and sedimentation (buildup of sediments behind dam)

Run of River System and Tidal Energy

• a dam diverts the natural current of a river through man-made channel beside the river

• natural current of the river turns the turbine 🡪 powers the generator 🡪 electricity

• less impactful to surrounding ecosystem since no reservoir is formed and ecosystems behind dam aren’t flooded

• doesn’t stop natural flow of sediments downstream like water impoundment systems do

• doesn’t generate nearly as much power and may be unavailable in warmer seasons when river water levels are lower

• Tidal power: comes from tidal ocean flow turning turbine (coastal areas only)

Drawbacks of Hydroelectricity Dams (Ecological/ Environmental/ Economic)

• Reservoir floods habitats behind dam (forests/wetlands 🡪 gone; river becomes a lake)

  • Sedimentation changes upstream and downstream conditions

    • Upstream becomes warmer (less CO₂) and rocky streambed habitats covered in sediment

    • Downstream loses sediment (important nutrient source), decreased water level, loses streambed habitat

  • Downstream wetlands especially suffer since nutrients in sediment doesn’t reach them

• Fossil fuel combustion during dam constriction, increased evaporation due to larger surface area in reservoir, and methane release due to anaerobic decomposition of organic matter in reservoir

• Human homes and business must be relocated due to reservoir flooding, initial construction is very expensive (does create long-term jobs though), sediment buildup must be dredged (removed by crane) eventually

  • Loss of ecosystem services from downstream wetlands, potential loss of fishing revenue if salmon breeding is disrupted

Fish Ladders

• Cement “steps” or series of pools that migratory fish like salmon can use to continue migration upstream, around or over dams

  • Enables continued breeding for salmon, food source for predators like large birds, bears, and fishing revenue for humans

  • “salmon cannon” is a similar alternative that enables salmon to be captured or directed into a tube that carries them over the dam

Benefits of Hydroelectric Dams

• No GHG emissions when producing electricity (initial construction does require cement and machines that emit GHGs)

  • Reservoir and dam can be tourist attractions

  • Jobs are created to maintain the dam

  • Reliable electricity source generated for surrounding area

  • No air pollutants released during electricity generation

• Allows for control of downstream seasonal flooding

6.10 Geothermal Energy

Geothermal Basics

• Natural radioactive decay of elements deep in earth’s core gives off heat, driving magma convection currents which carry heat to upper portion of mantle, close to earth’s surface

  • Water can be piped down into the ground and heated by this heat from the mantle

  • Hot water can be converted into steam 🡪 turbine 🡪 electricity can be used to heat homes directly

• Geothermal for electricity: naturally heated water reservoirs underground are drilled into and piped up to the surface (or water can be piped down into naturally heated rock layers)

  • The heat from magma turns the water into steam, which is forced through pipes to spin a turbine

  • Water is cooled in cooling tower and returned to the ground to start the process over

  • Renewable since heat from earth’s core won’t run out; but only if groundwater is returned after use

Ground Source Heat Pump

• Often referred to as “geothermal” but technically the heat does not come from geologic activity (comes from the ground storing heat from the sun)

  • More accurate name is “ground source heat pump”

  • 10 feet down, the ground stays a consistent 50-60 degrees due to holding heat from sun (not warmed by geothermal energy from magma – so not technically geothermal energy)

  • Heat absorbing fluid is pumped through a pipe into the ground where it either takes on heat from the ground, or gives off heat to the ground

Geothermal Heating

• True geothermal heating involves piping water deep into ground to be heated by magma and then transferring heat from water to the building

  • Different than ground source heat pump

  • Well must go thousands of meters (kms) down into the ground to reach heated water reservoir

  • Heated water is piped up to surface and sent to homes or business to heat them

Geothermal pros

• Potentially renewable, only if water is piped back into the ground for reuse

• Much less CO₂ emission than fossil fuel electricity

Geothermal Cons

• Not everywhere on earth has access to geothermal energy reaching close enough to surface to access it

• Hydrogen sulfide can be released, which is toxic and can be lethal to humans and animals

• Cost of drilling that deep in the earth can be very high initially

6.11 Hydrogen Fuel Cell

Hydrogen Fuel Cell Basics

• Use hydrogen as a renewable, alternative fuel source to fossil fuels

  • H₂ gas and O₂ are the inputs used to generate electricity; H₂O is given off as a waste product

• H₂ gas enters fuel cell where it’s split into protons and electrons by an electrolyte membrane that only lets protons pass through

  • Electrons take an alternative route (circuit) around the membrane, which generates an electrical current

  • O₂ molecules enter fuel cell break apart into individual O atoms and combine with two hydrogens to form H₂O as a by product

• Most common application is in vehicles

  • Replaces gasoline (non-renewable, GHG releasing and air pollution) with H fuel (no air pollutants released and only H₂O vapor)

Creating H₂ Gas

• key challenge to H fuel cells is obtaining pure H gas (because it doesn’t exist by itself as a gas naturally)

  • separating H₂ gas from other molecules like H₂O or CH₄ is very energy intensive

    • two main processes are steam reforming (95% of all H production) and electrolysis (less common, but more sustainable

  • stream reforming: burning natural gas (CH₄) and suing steam to separate the H gas from the methane (CH₄)

    • emits CO₂ and requires natural gas input

  • electrolysis: electrical current is applied to water, breaking it into O₂ and H₂

    • no CO₂ emission, but does require electricity

Hydrogen as an Energy Carrier (pros)

• because H₂ gas can be stored in pressurized tanks, it can be transported for use creating electricity later, in a different location

• can also be used as a fuel for vehicles (replacing gasoline) or to create ammonia for fertilizer, or in the chemical industry

Drawbacks of Hydrogen Fuel Cells

• since 95% of H₂ production requires methane (CH₄), H fuel cells are based on a non-renewable and CO₂ releasing energy source

  • if electrolysis is used, it’s only as sustainable as the electricity source

  • widespread H fuel cell use would require building widespread H distribution network (similar to current system for gasoline)

  • H fuel stored in gas form in vehicles would require much larger tanks than current gasoline tanks

6.12 Wind Energy

Wind Turbine Electricity Generation

• Kinetic energy of moving air (wind) spins a turbine; generator converts mechanical energy of turbine into electricity

• Blades of turbine are connected to gearbox by a shaft that rotates; rotating gears create mechanical energy that the generator transforms into electricity

  • Average turbine can power 460 homes

  • Motorized drive within shaft can turn the turbine to face wind

Wind Turbine Location

• Clustered in groups (wind projects or farms) in flat, open areas (usually rural)

  • Location them together makes service, repair, and building transmission lines to them easier

    • Can share land with agricultural use

• Offshore wind = wind farms in oceans or lakes

  • Capitalizes on faster wind speeds

  • Does require transmission lines bult across long distances to reach land though

Wind Energy Benefits and Drawbacks

6.13 Energy Conservation

Small Scale vs. Large Scale Energy Conservation

Sustainable Home Designs

• Ways to either block out or take advantages of sun’s natural heat, or keep in heating/cooling to decrease energy required

  • Deciduous shade trees for landscaping (leaves block sun in summer, but allow it in during winter)

  • Using passive solar design concepts to trap sun’s heat and decrease energy from heating system (heat absorbing walls, triple or double paned windows)

  • Well-insulated walls/attic to trap heat in winter and cool air from AC system in summer

  • This decreases electricity used by AC unit and energy used by heating system

Water Conservation

• Native plants require less watering than traditional lawns (also increase biodiversity of pollinators and require less fertilizer)

• Low-flow shoers, toilets, and dishwashers do the same job with less total water (less energy to purify and pump to homes)

• Rain barrels allow rain water to be used for watering plants or washing cars

Energy Conservation – Transportation

• ~28% of total US energy use comes from transport of goods and people

• Improving fuel economy of US fleet of vehicles conserves energy as less gasoline/diesel is needed to travel same distance

  • CAFE (Corporate Average Fuel Economy) standards are regulations set in US to require auto manufacturers to make cars that meet certain MPG standards, or pay penalties

• Hybrids have both a gasoline and electric engine, enabling them to have higher MPG ratings

  • Breaking system charges the electric battery, which powers electric motor

  • Electric vehicles (EVs or BEVs) use no gasoline, but still require electricity (only as sustainable as electricity source)

  • Public transit and carpooling are even better energy-saving transport options

Sustainable Building Design

• Decreasing the amount of energy required to build larger buildings and heat/cool them

  • Green roof or walls can decrease runoff, and absorb sun’s heat, decreasing energy needed for cooling building and surrounding area (lessens heat island effect)

  • Sun lights on rood, or windows on sides can decrease electricity used for lighting

  • Recycled materials can reduce energy required to produce new ones (glass, wood, even fly ash from coal can be used in foundation)

Managing Peak Demand and Smart Grid Technology

• Peak demand is the time of day or year (often early night time hours or very hot weather events) that electricity demand is highest

  • If demand exceeds supply, rolling blackouts occur

  • To manage peak demand, some utilities use a variable price model for electricity

    • Users pay a higher rate during peak demand hours or events, to discourage use

    • Users pay a lower rate/kWh when using a lower amount of energy (incentivizes lower overall use)

• “smart grid” is just the idea of managing demand and energy sources in a more varied way

Unit 7 Air Pollution

7.1 Introduction to Air Pollution (Pollutants)

• Air Pollution Basics

  • Write about air pollutants (specific molecules/particles) not just air “pollution” as an idea

  • Clean Air Act (1980) identified 6 criteria air pollutants that the EPA is required to set acceptable limits for, monitor, and enforce

    • SO₂ - Sulfur dioxide: coal combustion (electricity), respiratory irritation, smog, acid precipitation

    • NO_x – Nitrogen Oxides (NO & NO₂): all fossil fuel combustion, O₃ photochemical smog, acid precipitation

    • CO – Carbon monoxide: incomplete combustion, O₃, lethal to humans

    • PM – Particulate matter: fossil fuel/biomass combustion, respiratory irritation, smog

    • O₃ – Ozone (tropospheric): photochemical oxidation of NO₂, respiratory irritation, smog, plant damage

    • Pb – Lead: metal plants, waste incineration, neurotoxicant

• Air Pollutants vs. Greenhouse Gasses

  • CO₂ is not one of 6 criteria pollutants in Clean Air Act

    • CO₂ does not directly lower air quality from a human health standpoint

      • Not toxic to organisms to breath

      • Not damaging to lungs/ eyes

      • Does not lead to smog, decreased visibility

    • CO₂ is a greenhouse gas; it does lead to earth warming, and thus environment and human health consequences

  • Bottom line: in APES, CO₂ has not typically been included on FRQ scoring guides as an air pollutant (stick to SO₂, NO_x, O₃, PM)

• Coal Combustion

  • Releases more air pollutants than other fossil fuels

    • Releases CO, CO₂, SO₂, NO_x, toxic metals (mercury, arsenic, lead), and PM (0ften carries the toxic metals)

    • Impacts of SO₂

      • Respiratory irritant (inflammation of bronchioles, lungs), worsens asthma and bronchitis

      • Sulfur aerosols (suspended sulfate particles) block incoming sun, reducing visibility and photosynthesis

      • Forms sulfurous (grey) smog

      • Combines with water and O₂ in atmosphere to form sulfuric acid 🡪 acid precipitation

• Nitrogen Oxides (NO_x)

  • Released by combustion of anything, especially FFs and biomass

    • NO_x refers to nitrogen oxides (both NO and NO₂)

    • NO forms when N₂ combines with O₂ (especially during combustion)

    • NO can become NO₂ by reacting with O₃ or O₂

    • Sunlight converts NO₂ back into NO

  • Environment and Human Health Impacts

    • Respiratory irritant

    • Leads to tropospheric ozone (O₃) formation, which leads to photochemical smog

    • Combines with water and O₂ in atmosphere to form nitric acid 🡪 acid precipitation

• EPA and Lead

  • Before CAA< lead was a common gasoline additive; EPA began phaseout of lead from gasoline in 1974. Vehicles made after 1974 are required to have catalytic converters to reduce NO_x, CO, and hydrocarbon emissions (lead damages catalytic converters)

• Primary vs. Secondary Air Pollutants

  • Primary

    • Emitted directly from sources such as vehicles, power plants, factories, or natural sources (volcanoes, forest fires)

    • NO_x, CO, CO₂, VOCs, SO₂, PM, and hydrocarbons

  • Secondary

    • Primary pollutants that have transformed in presence of sunlight, water, O₂

    • Occur more during the day (since sunlight often drives formation

    • Tropospheric O₃ (ozone)

    • Sulfuric acid (H₂SO₄) and sulfate (SO₄^2-)

    • Nitric acid (HNO₃) and nitrate (NO₃^-)

7.2 Photochemical Smog

• Photochemical Smog Precursors and Conditions

  • Precursors

    • NO₂ – broken by sunlight into NO + O (free O + O₂ 🡪 O₃)

    • VOCs - volatile organic compounds (hydrocarbons) that bind with NO and form photochemical oxidants

      • Carbon-based compounds that volatize (evaporate) easily (this makes them “smelly”)

      • Sources: gasoline, formaldehyde, cleaning fluids, oil-based paints, even coniferous trees (pine smell)

    • O₃ – forms when NO₂ is broken by sunlight and free O binds to O₂

      • Respiratory irritant in troposphere (at earth’s surface)

      • Damaging to plants stomata, limiting growth

  • Conditions

    • Sunlight - drives O₃ formation by breaking down NO₂ 🡪 NO + O; then free O atom binds with O₂

    • Warmth – hotter atmosphere temperature speeds O₃ formation, evaporation of VOCs and thus smog formation

• Normal O₃ Formation

  • Morning commute leads to high NO₂ levels from car exhaust

  • Sunlight breaks NO₂ into NO + O

  • O bonds with O₂ to form O₃

  • O₃ formation typically peaks in afternoon when sunlight is most direct and NO₂ emissions from morning traffic have peaked

  • At night, O₃ reacts with NO to form NO₂ and O₂ once again; O₃ levels drop overnight

• Photochemical Smog Formation

  • Sunlight breaks NO₂ into NO + O

  • O bonds with O₂ to form O₃

  • VOCs bonds with NO to form photochemical oxidants

  • Without NO to react with, O₃ builds up instead of returning to O₂ and NO₂ overnight

  • O₃ combines with photochemical oxidants (NO + VOCs) to form photochemical smog

• Factors that Increase Smog Form

  • Increased vehicle traffic; increases NO₂ emissions and therefore O₃ formation

  • Higher VOCs emissions (gas stations, laundromats, petrochemicals, and plastic factories)

  • More sunlight (summer, afternoon) = more O₃

  • Warmer temperature, speeds evaporation of VOCs and reaction that lead to O₃

  • Urban areas have more smog due to all of these factors

• Impacts of Smog

  • Environment (reduces sunlight; limiting photosynthesis, O₃ damages plants stomata and irritates animal respiratory tracts)

  • Humans (respiratory irritant; worsens asthma, bronchitis, COPD; irritates eyes)

  • Economic (increased health care costs to treat asthma, bronchitis, COPD, lost productivity due to sick workers missing work or dying, decreased agriculture yields due to less sunlight reaching crops and damage to plant stomata)

• Reduction of Smog

  • Vehicles (decreasing the number of vehicles on road decreases NO₂ emissions, fewer vehicles = less gas = fewer VOCs)

  • Energy (increased electricity production from renewable sources that don’t emit NO_x (solar, wind, hydro), natural gas power plants release far less NO_x than coal)

7.3 Thermal Inversion

• Urban Heat Island Effect

  • Urban areas tend to have higher surface and air temperature than surrounding suburban and rural areas due to:

  • Lower albedo: concrete and asphalt absorb more of sun’s energy than areas with more vegetation (absorbed sunlight is given off as IR radiation – heat)

  • Less evapotranspiration: water evaporating from surfaces and transpiration from plants carries heat from surface into the atmosphere

    • this cools off rural and suburban areas which have more vegetation

• Thermal Inversion

  • Normally the atmosphere is warmest at earth’s surface, and cools as altitude rises. Because warm air rises, air convection carries air pollutants away from earth’s surface and distributes them higher into the atmosphere

  • During a thermal inversion, a cooler air mass becomes trapped near earth’s surface

    • due to a warm front moving in over it

    • or due to hot urban surfaces colling overnight while IR radiation absorbed during the day is still being released

  • because cold air at the surface is trapped beneath the warmer mass above, convection doesn’t carry pollutants up and away.

• Effects of Thermal Inversion

  • Air pollutants (smog, PM, ozone, SO₂, NO_x) trapped closer to earth

  • Respiratory irritation: asthma flare ups leading to hospitalization, worsened COPD, emphysema

  • Decreased tourism revenue

  • Decreased photosynthetic rate

7.4 Atmospheric CO₂ and PM

• Natural Sources of Air Pollutants

  • Lighting strikes (convert N₂ in atmosphere to NO_x)

  • Forest fires (CO, PM, NO_x, combustion of biomass also releases CO₂ and H₂O vapor) (greenhouse gasses)

  • Plants (especially conifers) (plants emit VOCs)

  • Volcanoes (SO₂, PM, CO, NO_x)

• Natural Sources of CO₂ and PM

  • Respiration (all living thins release CO₂ through respiration)

  • Natural PM Sources (sea salt, pollen, ash from forest fires, volcanoes, and dust leads to haze)

  • Aerobic Decomposition (decomposition of organic matter by bacteria and decomposers in the presence of oxygen 🡪 releases CO₂)

  • Anaerobic decomposition (decomposition of organic matter by bacteria and decomposers in low or oxygen-free conditions 🡪 releases CH₄ (methane))

• PM₁₀ vs PM_2.5

  • Particulate matter: solid or liquid particles suspended in air (also referred to as “particulates”)

  • PM₁₀ (< 10 micrometers)

    • Particles or droplets like dust, pollen, ash, or mold

    • Too small to be filtered out by nose hairs and trachea cilia; can irritate respiratory tract and cause inflammation

  • PM_2.5 (< 2.5 micrometers)

    • Particles from combustion (especially vehicles) smaller dust particles

    • More likely to travel deep into the lungs due to smaller size

    • Associated with chronic bronchitis and increased risk of lung cancer

7.5 Indoor Air Pollutants

• Developing Countries

  • Developing nations use more subsistence fuels such as wood, manure, charcoal (biomass)

  • These biomass fuels release CO, PM, NO₂, VOCs (can also cause deforestation)

  • Often combusted indoors with poor ventilation, leading to high concentrations

• Developed Countries

  • Developed nations use more commercial fuels (coal, oil, natural gas) supplied by utilities

  • Typically burned in closed, well ventilated furnaces, stoves, etc.

  • Major indoor air pollutants in developed nations come from chemicals in products: adhesives in furniture, cleaning supplies, insulation, lead paint

• PM and Asbestos

  • Particulates (PM) are common indoor air pollutant

  • Asbestos is a long, silicate particle previously used in insulations (since been linked to lung cancer and asbestosis)

• CO (Carbon Monoxide)

  • CO is an asphyxiant: causes suffocation due to CO binding to hemoglobin in blood, displacing O₂

  • Lethal to humans in high concentrations, especially with poor ventilation (odorless and colorless – hard to detect)

  • Developed nations: CO released into home by malfunctioning natural gas furnace ventilation

  • Developing nations: CO emitted from indoor biomass combustion for heating/cooking

• VOCs (Volatile Organic Compounds)

  • Chemicals used in a variety of home products that easily vaporize, enter air, and irritate eyes, lungs, bronchioles

  • Adhesives/sealants: chemicals used to glue carpet down, hold furniture together, seals panels

  • Formaldehyde is a common adhesive in particle board and carpet glues

  • Cleaners: common household cleaners and deodorizers such as Febreze

  • Plastics and Fabrics: both can release VOCs themselves, or from adhesives used in production

• Radon Gas

  • Radioactive gas released by decay of uranium naturally found in rocks underground (granite especially)

  • Usually enters homes through cracks in the foundation and then disperse up from basement/foundation through home

  • can also seep into groundwater sources and enter body through drinking water

• Dust and Mold

  • Natural indoor air pollutants that can worsen asthma, bronchitis, COPD, emphysema

  • Dust settles in homes naturally, is disturbed by movement, entering air and then respiratory tract

  • Mold develops in areas that are dark and damp and aren’t well ventilated

• Lead

  • Found in paint in old homes

  • Paint chips off walls/windows and is eaten by small children or inhaled as dust

7.6 Reduction of Air Pollutants

• Reducing Emissions

  • Reducing emissions = reducing air pollutants

• Law/Regulations

  • Clean Air Act

    • Allows EPA to set acceptable levels for criteria air pollutants

      • Monitor emissions levels from power plants and other facilities

      • Tax/sue/fine corporations that release emissions above levels

  • CAFE Vehicle Standards

    • (Corporate Average Fuel Economy) standards require the entire US fleet of vehicles to meet certain average

      • Requires vehicle manufacturers to work to make more efficient vehicles

      • More efficient vehicles burn less gasoline and release less NO_x, PM, CO, and CO₂

  • Pollution Credits

    • Similar to ITQs for fish

    • Companies that reduce emissions below EPA-set levels earn pollution credits

• Reducing Vehicle Air Pollutants

  • Vapor Recovery Nozzle

    • Capture hydrocarbon VOCs released from gasoline fumes during refueling

      • Separate tubes inside nozzle captures vapors and returns them to underground storage tank beneath the gas station

      • Reduces VOCs, which contribute to smog and irritate respiratory tracts

      • Reduces benzene (carcinogen) released from gasoline vapors

  • Catalytic Converter (CC)

    • Required on all vehicles after 1975

    • Contains metals (platinum and palladium) that bind to NO_x and CO

      • CC converts NO­_x, CO, and other hydrocarbons into CO₂, N₂, O₂, and H₂O

• Reducing SO_x­ and NO_x

  • Crushed Limestone (SO₂)

    • Used to reduce SO₂ from coal power plants

    • Crushed coal mixed with limestone (calcium carbonate) before being burned in boiler

    • Calcium carbonate in limestone combines with SO₂ to produce calcium sulfate, reducing the SO₂ being emitted

    • Calcium sulfate can be used to make gypsum wallboard or sheetrock for home foundations

  • Fluidized Bed Combustion (NO_z)

    • Fluidizing jets of air pumped into combustion “bed”

    • Jets of air bring more 0₂ into reaction, making combustion more efficient and bringing SO₂ into more contact with calcium carbonate in limestone

      • Also allows coal to be combusted at lower temperature, which emits less NO_x

• Wet and Dry Scrubbers

  • Dry Scrubbers (NO_x, SO_x, VOCs)

    • Large column/tube/pipe filled with chemicals that absorb or neutralize oxides (NO_x, SO_x, VOCs_ from exhaust streams (emissions)

      • Calcium oxide is a common dry scrubber additive which reacts with SO₂ to form calcium sulfite

  • Wet Scrubbers (NO_x, SO_x, VOCs + PM)

    • May involve chemical agents that absorb or neutralize NO_x, SO_x, VOCs, but also include mist nozzles that trap PM in water droplets as well

• Reducing Particulate Matter

  • Electrostatic Precipitator

    • Power plant/factory emissions passed through device with a negative charge electrode, giving particles a negative charge

    • Negative charged particles stick to positive charged collection plates, trapping them

    • Plates discharged occasionally so particles fall down into collection hopper for disposal in landfills

  • Baghouse Filter (PM)

    • Large fabric bag filters that trap PM as air from combustion/industrial process passes through

    • Shaker device knocks trapped particles loose into collection hopper below

7.7 Acid Rain

• Sources of NO_x and SO₂

  • NO_x and SO₂ are the primary pollutants that cause most acid precipitation

  • Major Sources

    • SO­₂ – coal fired power plants, metal factories, vehicles that burn diesel fuel

    • NO_x – vehicle emissions, diesel generators, coal power plants

  • Limiting Acid Rain

    • Reducing NO­_x and SO₂ emissions reduces acid deposition

      • Higher CAFE standards

      • More public transit

      • Renewable energy sources

      • More efficient electricity use

    • Since passage of Clean Air Act, acid deposition has decreased significantly

• NO_x and SO₂ react with O₂ and H₂O in the atmosphere, forming nitric and sulfuric acid

• Sulfuric acid and nitric acid dissociate in the presence of water into sulfate and nitrate ions, and hydrogen ions (H⁺)

• Acidic rain water (higher H+ concentration) decreases soil and water pH; can limit tree growth in forests down wind from major SO₂ and NO_x sources

• Environmental Effects of Acid Rain

  • Acidity= higher H+ ion concentration, lower pH

  • Soil/water acidification

    • H+ ions displace or leech other positive charged nutrients (Ca²⁺, K⁺) from soil

    • H+ ions also make toxic metals like aluminum and mercury more soluble in soil and water

  • pH Tolerance

    • as pH decreases (more acidic) outside optimal range for a species, population declines

      • when pH leaves range of tolerance, they cannot survive at all due to aluminum toxicity and disrupted blood osmolarity

  • indicator species can be surveyed and used to determine conditions of an ecosystem

• Mitigating Acid Rain

  • Limestone (calcium carbonate) is a natural base that can neutralize acidic soil/water

  • Limestone

    • Calcium carbonate (CaCO₃) reacts with H+ ions, forming HCO₃ and giving off Ca²⁺

      • This “neutralizes” acidic water/soil, moving it closer to a pH of 7

    • Regions with limestone bedrock have some natural buffering of acid rain

      • Humans can also add crushed limestone to soils/waters to neutralize

    • Acid rain can corrode human structures, especially those made from limestone

  • Limiting SO_x and NO_x

    • Decreasing these primary pollutants that drive acid rain can reduce it

      • Renewable energy sources, decreasing coal comb.

      • Fluidized bed combustion and lower burning temperature for existing coal power plants

      • Dry or wet scrubbers

7.8 Noise Pollution

• Urban Noise Pollution

  • Any noise at great enough volume to cause physiological stress (difficulty communicating, headaches, confusion) or hearing loss

  • Construction: jack hammers, trucks, concrete pouring

  • Transportation: cars, busses, trains

  • Industrial activity: manufacturing plants

  • Domestic activity: neighbor’s music, lawn mowing, home projects

• Wildlife Effects (land)

  • Noise pollution can disrupt animal communication, migration, and damage hearing

  • Physiological stress: caterpillar hearts beat faster when exposed to simulated highway noise pollution

  • Hearing: can prevent predators from hearing prey and vice versa; can prevent mates from locating each other (both decrease chances of survival)

• Wildlife Effects (aquatic)

  • Aquatic noise pollution comes from the noise of ship engines, military sonar, and seismic air blasts from oil and gas surveying ships

  • Physiological stress: hearing loss, disrupted communication, mating calls, predator and prey navigation

    • whales are especially prone to having migration routes disrupted as their vocal communication is disrupted

  • Seismic surveying: ships send huge air blasts down into the water, searching for oil by recording how the echo is returned from ocean floor

    • So loud that researchers off the coast of Virginia can detect blasts from coast of Brazil

Unit 8 Aquatic and Terrestrial Pollution

8.1 Sources of Pollutants

• Point Source Pollutants

  • Pollutant that enters environment from an easily identified and confined place, you can point to it

• Nonpoint Source Pollutants

  • Pollutants entering the environment from many places at once. Difficult to “point” to one individual source

• Must-Know Pollution Examples

  • Point source

    • Animal waste runoff from a CAFO (ammonia, fecal coliform bacteria)

    • Emissions from smokestack of a coal power plant (CO₂, NO_x, SO₂, PM)
      BP Oil Spill (hydrocarbons, benzene)

  • Nonpoint Source

    • Urban runoff (motor oil, nitrate, fertilizer, road salt, sediment)

    • Pesticides sprayed on agricultural fields; carried by wind and washed off large agricultural regions into bodies of water

  • Estuaries and bays are polluted by many nonpoint pollution sources from the large watersheds that empty into them

• Pollutants vs Pollution

  • Pollutants

    • Specific chemicals or groups of chemicals from specific sources with specific environmental and human health effects

  • Pollution

    • Vague, nondescript term for any substance that is harmful to the environment (never acceptable on APES FRQ)

8.2 Human Impacts on Ecosystems

• Range of Tolerance

  • Organisms have range of tolerance for abiotic conditions in the habitat (pH, temperature, salinity, sunlight, nutrient levels (ammonia and phosphate))

  • Organisms also have range of tolerance for pollutants that human activities release into their habitats

    • Pollutant cause physiological stress such as

      • Limited growth

      • Limited reproductive function

      • Difficulty respiring, potentially asphyxiation

      • Hormonal disruption

      • Death (if concentration of pollutants is high enough)

• Temperature Tolerance of Reef Algae

  • Coral reef = mutualistic relationship between coral and photosynthetic algae called zooxanthellae; algae supply sugar and coral supply CO₂ + detritus (nutrient containing organic matter)

  • Algae have narrow temperature tolerance and leave the reef when temperatures rises

    • Pollutants from runoff (sediments, pesticides, and sunscreen) can also force algae from reef

  • Coral lose color and become stressed and vulnerable to disease without algae (main food source)

• Human Impacts on Coral Reef

  • Humans disrupt coral reef ecosystems via greenhouse gas emissions (warming ocean temperature and bleaching coral)

  • Overfishing decreases fish populations in coral reef ecosystem and bottom trawling can break reef structure and stir up sediment

  • Urban and agricultural runoff also damages coral reef ecosystems

    • Sediment pollution: sediment carried into ocean by runoff makes coral reef waters more turbid, reducing sunlight (photosynthesis)

    • Toxicants: chemicals in sunscreen, oil from roadways, pesticides, from agricultural runoff

    • Nutrients (P/N): ammonia from animal waste, nitrates/phosphates from agriculture or lawn fertilizers

• Oil Spill Effects

  • Hydrocarbons in crude oil (petroleum) are toxic to many marine organisms and can kill them, especially if they ingest the oil or absorb through gills/skin

  • Oil can wash ashore and decrease tourism revenue and kill fish, decreasing fishing industry revenue, hurt restaurants that serve fish

  • oil can settle deep in root structures of estuary habitats like mangroves or salt marshes

• Oil Spill Clean Up

  • Oil spills can occur when an underwater oil well explodes/blows out or when a tanker runs into a rock/iceberg and is punctured

  • Cleanup can involve booms on surface to contain spread and ships with vacuum tubes to siphon oil off of the surface or devices to skim it off

  • Physical removal of oil from beach sand and rocks with towels, soaps, and shovels

  • Chemical dispersants sprayed on oil slicks to break up and sink to the bottom

  • Burning oil off surface

8.3 Endocrine Disruptors and Industrial Water Pollutants

• Endocrine Disruptors

  • Chemicals that interfere with the endocrine (hormonal) systems of animals

  • Bind to cellular receptors meant for hormones, blocking the hormone from being received, or amplifying its effects

  • Atrazine – broad spectrum herbicide used to control weeds and prevent crop loss

  • DDT – broad spectrum insecticide that was phased out, but still persists in environment

  • Phthalates – compound used in plastic and cosmetic manufacturing

  • Lead, Arsenic, Mercury – heavy metals

  • Many human medications that enter sewage via human urine or flushed meds

• Mercury – naturally occurring in coal, released by anthropogenic activities

  • Coal combustion, trash incineration, burning medical waste, heating limestone for cement

  • Endocrine disruptor: inhibits estrogen and insulin (interferes with menstrual cycle and ovulation)

  • Teratogen: (chemical harmful to developing fetuses) can accumulate in fetus brain

  • Mercury itself isn’t toxic but bacteria in water sources convert it to methylmercury which is highly toxic to animals

• Arsenic – naturally occurring element in rocks underground that can dissolve into drinking water; natural release into groundwater can be worsened by mining

  • Anthropogenic sources: formerly in pesticides applied to agricultural fields

  • Carcinogenic (lung, bladder, kidneys) and endocrine disruptor

• Lead – found in old paint (in homes), old water pipes, and soils contaminated by PM from vehicle exhaust before lead was phased out of gas in 70s

  • Neurotoxicant

  • Endocrine disruptor

• Coal Ash

  • Coal ash can be a source of mercury, lead, and arsenic

8.4 Human Impacts on Wetlands and Mangroves

• Wetlands

  • An area with soil submerged/saturated in waters for at least part of the year but shallow enough for emergent plants

  • Ecosystem services of wetlands:

    • Provisioning: habitat for animal and plant foods

    • Regulating: groundwater recharge, absorption of floodwater, CO₂ sequestration

    • Supporting: H₂O filtration, pollinator habitats, nutrient cycling, pest control

    • Cultural: tourism revenue, fishing license, camping fees

• Threats to Wetlands

  • Pollutants – nutrients, sediment, motor oil, pesticides, endocrine disruptors

  • Development

8.5 Eutrophication

• extra input of N and P lead to eutrophication which fuels algae growth

• algae bloom due to increase of N/P 🡪 decreased sunlight 🡪 plants below surface die 🡪 bacteria use up O₂ for decomposition 🡪hypoxia (low O­₂) and dead zones

• Major N/P sources:

  • Discharge from sewage treatment plants

  • Animal waste from CAFOS

  • Synthetic fertilizer from agriculture fields and lawns

• Oligotrophic Waterways

  • Waterways with low nutrient levels, stable algae populations, and high dissolved oxygen

  • Aquatic ecosystems naturally undergo succession

  • sediment buildup on bottom (benthic zone) leads to higher nutrient levels

  • overtime, ponds naturally shift form oligotrophic, to mesotrophic, to eutrophic

• Dissolved Oxygen and Dead Zones

  • Decreased in dissolved oxygen (hypoxia) is what causes a dead zone

    • All aquatic life requires dissolved oxygen in water for respiration

8.6 Thermal Pollution

• Solubility of Oxygen and Temperature

  • Solubility = the ability of a solid/liquid/gas to dissolve into a liquids

  • Inverse relationship between water temperature and oxygen solubility (water temp goes up, DO goes down)

  • Thermal pollution: when heat released into water has negative effects on organisms living in water. Heat increases respiration rate of aquatic organisms (thermal shock). Hot water has less O₂.

• Source of Thermal Pollution

  • Power plants use cool water from surface/groundwater sources nearby to cool steam used to turn a turbine back into water reuse

  • Urban stormwater runoff can also cause thermal pollution due to heat from blacktop/asphalt

  • Nuclear power plants require especially large amounts of cool water to cool steam back into water and to cool the reactor

• Cooling Towers

  • Cooling towers/ponds are used to cool steam back into water and to hold warmed water before returning to local surface water

8.7 Persistent Organic Pollutants (POPs)

• POPs

  • Persistent (long-lasting) Organic (carbon based) Pollutants

  • Synthetic compounds that do not easily breakdown in the environment; accumulate and buildup in water and soil

  • Fat-soluble, meaning they also accumulate and persist in animals’ fat tissue instead of passing through the body

  • Sources: pesticides, medications, dioxins, PCBS, perchlorates

  • POPs travel long distances through wind and water, impacting ecosystems far away

8.8 Biomagnification

• Bioaccumulation

  • Absorption and concentration of compounds in the cells and fat tissues of organisms

• Biomagnification

  • Increasing concentrations of fat-soluble compounds like methylmercury and POPs in each level up the trophic pyramid or food web/chain

  • Biomagnification begins with POPs or methylmercury in sediments or plants in an ecosystem

  • DDT was banned in may developed nations but still persists in sediments of many bodies of water

  • Mercury is emitted from burning coal and by volcanoes, carried by wind, and deposited in water where bacteria converts it into methylmercury

8.9 Solid Waste Disposal

• Solid Waste Types and Sources

  • MSW (municipal solid waste): solid waste from cities, waste “stream” refers to flow of solid waste to recycling centers, landfills, or trash incineration facilities, aka trash litter garbage refuse

  • E-Waste: old computers phones tablets, only ~2% of MSW; considered hazardous waste due to metals like cadmium lead mercury and PBDEs (fireproof chemicals)

  • can leach endocrine disrupting chemicals out of landfills if thrown away with regular MSW

• Sanitary Landfills

  • Clay/plastic bottom liner: layer of clay/plastic on the bottom of a hole in the ground; prevents pollutants from leaking out into soil/groundwater

  • Leachate Collection System: system of tubes/pipes at bottom to collect leachate (water draining through waste and carrying pollutants) for treatment and disposal

  • Methan Recovery System: system of tubes/pipes to collect the methane produced by anaerobic decomposition in the landfill

    • Methan can be used to generate electricity or heat buildings

  • Clay Cap: clay-soil mixture used to cover the landfill once it’s full; keeps out animals, keeps in smell, and allows vegetation to regrow

• Landfill Issues

  • Landfills have environmental impacts like groundwater contamination and release of GHGs

    • Groundwater can be contaminated with heavy medals, acids, medications, and bacteria if leachate leaks through lining into soil/groundwater beneath

    • Greenhouse gases are released from landfills due to decomposition; both contribute to global warming and climate change

  • Not in my back yard (NIMBY) = idea that communities don’t wat landfills near them for a number of reasons

  • Landfills are often placed near low-income or minority communities that don’t have the resources or political power to fight against these decisions

• Waste Incineration and Ocean Dumping

  • Waste can be incinerated to reduce the volume that needs to be landfilled; since most waste = hydrogen, carbon, and oxygen

  • Can be burned to generate electricity

  • Illegal ocean dumping occurs in some countries with few environmental regulations or lack of enforcement

8.10 Waste Reduction

• Reduce, Reuse, Recycle

  • Reducing consumption is the most sustainable because it decreases natural resources harvesting and the energy inputs to creating, packaging, and shipping goods

  • Recycling = processing and converting solid waste material into new products

    • Least sustainable of the three Rs due to the amount of energy it requires to process and convert waste materials

• Pros of Recycling

  • Reduces demand for new materials, especially metals and wood which cause habitat destruction and soil erosion when harvested

• Cons of Recycling

  • Recycling is costly and still requires significant energy

• Composting

  • Organic matter (food scraps, paper, yard waste) being decomposed under controlled conditions

  • Reduces landfill volume and produces rich organic matter

  • Potential drawback includes the foul smell that can be produced if not properly rotated and aerated and rodents or other pests that may be attracted

• E-Waste

  • Waste from electronic that often contain heavy metals (lead, mercury, cadmium)

    • Can leach these toxic metals into soil and groundwater if disposed of in landfills or open dump

  • Can be recycled and reused to create new electronics

• Waste to Energy

  • Waste can be incinerated to reduce the volume and also generate electricity; most waste (paper, plastic, food) = hydrogen, carbon, and oxygen so it easily combusts at high temperatures

  • Methane gas produced by decomposition in landfill can be collected with pipes and burned to generate electricity

8.11 Sewage Treatment

• Water Treatment Process

1. Primary Treatment (physical removal of large debris with a screen or gate)

2. Secondary Treatment (biological breakdown of organic matter (feces) by bacteria; aerobic process that requires O₂)

3. Tertiary Treatment (ecological or chemical treatments to reduce pollutants left after primary and secondary)

4. Disinfectant (UV light, ozone, or chlorine is used to kill bacteria or other pathogens, such as e. Coli)

• Effluent: liquid waste (sewage) discharged into a surface body of water, typically from a wastewater treatment plant

  • Sludge: inorganic, solid waste that collects at the bottoms of tanks in primary and secondary treatment

• Tertiary Treatment

  • Uses chemical filters to remove more nitrates and phosphate from secondary treatment discharge

• Sewage Treatment Issues

  • Combined sewage and stormwater runoff systems can cause wastewater treatment plants to flood during heavy rains, releasing raw sewage into surface water

  • Even treated wastewater effluent released into surface water often has N/P levels and endocrine disruptors

8.12 and 8.13 LD₅₀ and Dose Response Curve

• Dose Response Studies and LD₅₀

  • Studies that expose an organism to different doses of concentrations of a chemical in order to measure the response of the organism

  • Independent variable = concentration of the chemical

  • dependent variable = response measured in organism

  • LD₅₀ refers to the dose or concentration of the chemical that kills 50% of the population being studied

• Dose Response Curve

  • The data from a dose response study, graphed with percent mortality or other effect on the y-axis and dose concentration of chemical an x-axis

  • Lowest dose where an effect (death, paralysis, cancer) starts to occur is called the threshold or toxicity threshold

  • Dose response curves are usually “S=shaped” – low mortality at low doses, rapid increase in mortality as dose increases, level off near 100% mortality at high dosage

• ED₅₀ and Other Dose Responses

  • ED₅₀ refers to the dose concentration of a toxin or chemical that causes a non-lethal effect (infertility, paralysis, cancer, etc.) in 50% of the population being tested

• Dose Response Data and Human Health

  • Dose-response studies for toxic chemicals are not done on humans; data from other mammals are used to stimulate human toxicity

8.14 Pollution and Human Health

• Routes of Exposure

  • Ways that a pollutant enters the human body

    • Lead 🡪 water pipes and paint chips

    • Mercury 🡪 seafood (tuna)

    • CO 🡪 indoor biomass comb.

    • PM 🡪 pollen, dust, etc.

    • Arsenic 🡪 rice, groundwater

• Synergism

  • The interaction of two or more substances to cause an effect greater than each of them individually

    • Ex. Asthma caused by PM from coal PPs and Covid-19 damaging lungs

    • Carcinogenic effect of asbestos combined with lung damage from smoking

  • Synergisms make it especially hard to pinpoint the exact effects of one specific pollutant on humans

• Dysentery

  • Bacterial infection caused by food or water being contaminated with feces (often from sewage release into rivers and streams used for drinking water)

  • Causes intestinal swelling and can result in blood in feces

  • Can be treated with antibiotics that kill the bacteria causing the infection and access to treated/filtered water that can rehydrate

• Mesothelioma (asbestos)

  • A type of cancerous tumor caused by exposure to asbestos, primarily affecting the lining (epithelium) of the respiratory tract, heart, or abdominal cavity

  • Asbestos exposure comes primarily from old insulation materials used in attics, ceiling and flooring boards; when the insulation becomes physically disturbed, asbestos particles are released into the air and inhaled

• Tropospheric Ozone (O₃)

  • Worsens respiratory conditions like asthma, emphysema, bronchitis, COPD

  • Limits overall lung function

  • Irritates muscles or respiratory tract causing constriction of airways and shortness of breath

  • Sources: photochemical breakdown of NO₂ (car exhaust, coal, and NG combustion)

  • Only harmful in troposphere (beneficial in stratosphere)

8.15 Pathogens and Infectious Diseases

• Pathogens

  • A living organism (virus, bacteria, fungus, protist, worm) that causes an infectious disease

    • Infectious diseases are capable of being spread or transmitted (HIV, Ebola, Covid-19); noninfectious diseases are not transmissible (heart disease, asthma, cancer, diabetes)

    • Pathogens adapt and evolve to take advantage of humans as hosts for their reproduction an d spread (Covid-19 is a SARS-associated coronavirus that evolved to become especially effective at surviving and reproducing in humans)

• Vectors

  • A living organism (rat, mosquito) that carry and transmit infectious pathogens to other organisms

    • Climate change is shifting equatorial climate zones north and south away from the equator; this brings warmer temperatures to subtropical and temperate regions

    • Warmer temperatures allow pathogens and their vectors (mosquitos) to spread north and south to parts of the world previously too cold

      • Many pathogenic bacteria and viruses survive and replicate better in warmer weather

• Infectious Disease and Development

  • Less developed, poorer countries typically have higher rates of infectious disease

    • Less sanitary waste disposal; pathogens can reproduce in open waste areas where children may play or animals may scavenge and pass to humans

    • Less access to healthcare facilities and antibiotic medications to treat infectious diseases caused by bacteria and other pathogens

    • Lack of treatment/filtration for drinking water and sewage treatment exposes people to bacterial and viral pathogens in water, often from human waste

    • Tropical climates and more open-air living can expose people to vectors like mosquitoes; less money for vector eradication (spraying mosquito breeding grounds)

• Plague

  • Bacterial (pathogen) infection transmitted by fleas (vector) that attach to mice and rates (vectors as well)

  • Transmitted by flea bite, rodent contact or contaminated human fluids

  • Aka “bubonic” or “black” plague; modern antibiotics are highly effective against it, but some isolated instances still occur

• Tuberculosis (TB)

  • Bacterial (pathogen) infection that targets the lungs

  • Transmitted by breathing bacteria from body fluids of an infected person, which can linger in air for hours

  • Causes night sweats, fever, coughing blood; treatable in developed nations with access to powerful antibiotics

• Malaria

  • Parasitic protist (pathogen) infection caused by bite from infected mosquitoes

  • Most common in sub-Saharan Africa and other tropical regions

• West Nile

  • Virus (pathogen) infection caused by bite from infected mosquitoes (vector)

  • Birds are the main host but the virus can be transmitted to humans by mosquitoes that bit infected birds

  • Causes brain inflammation

• Zika Virus

  • Virus (pathogen) infection caused by bite from infected mosquitoes (vector) and sexual contact

  • Causes babies to be born with abnormally small heads and damaged brains; can be passed from mother to infant

  • No known treatment currently, so prevention is focused on eliminating mosquito populations

• Sars (severe acute respiratory syndrome)

  • Coronavirus (pathogen) infection caused by respiratory droplets from infected person

  • Primarily transmitted by touching or inhaling fluids from an infected person

  • Causes a form a pneumonia

  • Initial outbreak was in Southeast Asia

  • SARS-CoV-2 is the virus that causes the disease COVID-19

• MERS (Middle East Respiratory Syndrome)

  • Virus (pathogen) respiratory infection transmitted from animals to humans

  • Originated on Arabian Peninsula

• Cholera

  • Bacterial (pathogen) infection caused by drinking infected water

  • Vomiting, muscle cramps, and diarrhea; can cause severe dehydration

  • Can be introduced by water contaminated with human feces or undercooked seafood