Biomes

Terrestrial

Deserts:

• Defined in terms of the amount of rainfall they receive, not temperature.

• They cover about 20% of Earth’s surface and occur where rainfall is less than 20 inches (50 cm) per year.

• Daily extremes in temperature result from exceptionally low humidity as water vapor tends to block solar radiation.

• Most deserts are located between 15° and 35° north and south latitudes.

Tropical Rainforest:

• Animals include numerous birds, bats, small mammals, and insects.

• Decomposition is rapid and soils are subject to heavy leaching.

• Distinct seasonality where winter is absent and only two seasons are present.

• The length of daylight is 12 hours and varies a little year-round

• Large diversity of species.

• Occur near the equator.

Temperate Deciduous Forests:

• Occur in eastern North America, northeastern Asia, and western and central Europe.

• Have a distinct winter, moderate climate, and a 140–200-day growing season during four to six frost-free months.

• Temperature varies from –20°F to 85°F (–30°C to 30°C).

• Precipitation averages 30–60 inches (75–150 cm) per year.

• Fertile soil is enriched by decaying leaf litter.

Temperate Coniferous Forest:

• Found in temperate regions with warm summers, cool winters, and enough rainfall to support forests.

• Common in coastal areas with mild winters and heavy rainfall, or inland in drier climates or mountains.

• These forests have cedar, cypress, fir, juniper, pine, redwood, and spruce.

• These forests have two layers:

  • Overstory: The uppermost trees in a forest.

  • Understory: Layer made up of young trees, short species of trees, shrubs, and soft-stemmed plants.

• Some forests have a shrub layer.

• Grassy understories in pine forests often burn in ecologically important wildfires.

Taiga:

• Largest terrestrial biome; found in northern Eurasia, North America, Scandinavia, and two-thirds of Siberia.

• The harsh climate in the taiga limits both productivity and resilience.

  • Cold temperatures, wet soil during the growing season, and needle and moss acids slow organic matter decay.

• Seasons are divided into:

  • Short, moist, moderately warm summers

  • Long, dry, freezing winters.

Savannas:

• Savannas: These are grasslands with scattered individual trees and cover almost half the surface of Africa and large areas of Australia, South America, and India.

• Savannas are found in warm or hot climates with an annual rainfall of 20 to 50 inches (50–130 cm) concentrated in six to eight months, followed by a long drought when fires can occur.

• Savanna soil drains quickly and has a thin layer of humus to nourish vegetation.

  • Grass and small broad-leafed plants dominate.

  • Deciduous trees and shrubs are scattered across the open landscape.

  • Seasonal fires help savannas' biodiversity during dry and rainy seasons.

Temperate Grasslands:

• Temperate Grasslands: Here grasses are the dominant vegetation, while trees and large shrubs are absent.

• Examples of temperate grasslands include

  • the veldts of South Africa,

  • the pampas of Argentina,

  • the steppes of Russia, and

  • the plains and prairies of central North America.

• Climate is characterized by hot summers and cold winters, and rainfall is moderate.

  • Taller grasses grow in wetter areas.

  • Drought and fires affect biodiversity in the savanna.

• Deep, multi-branched grass roots grow and decay in the dark, fertile soil, enriching it.

  • Rotted roots bind to soil and feed plants.

• Seasonal drought, fires, and large mammal grazing prevent woody shrubs and trees from establishing.

  • In river valleys, cottonwoods, oaks, and willows grow, along with some flowers.

Tundra:

• Tundra: It has extremely low temperatures, large repetitive population changes, limited soil nutrients, little precipitation, low biotic diversity, poor drainage, short growing and reproductive seasons, and simple vegetation structure.

• Due to the Arctic tundra's unique conditions, the biota is highly specialized and sensitive to environmental change.

  • Dead organic material functions as a nutrient pool in the tundra.

Aquatic

Marine:

• Oceans cover approximately 75% of Earth’s surface and have a salt concentration of about 3%.

• Evaporation of seawater is the primary source of most of the world’s rainfall.

• Ocean temperatures affect cloud cover, surface temperature, and wind patterns.

• Marine algae and photosynthetic bacteria absorb carbon dioxide and produce oxygen in the oceans.

• Oceans have the highest net primary productivity per unit area of Earth.

• Littoral Zone: Also known as the intertidal zone, it is the part of the ocean that is closest to the shore.

• Neretic Zone: Also known as the sublittoral zone, this zone extends to the edge of the continental shelf.

• Photic Zone: The uppermost layer of water in a lake or ocean that is exposed to sunlight down to the depth where 1% of surface sunlight is available.

Lakes:

• These are large natural bodies of standing freshwater formed when precipitation, runoff, or groundwater seepage fills depressions in Earth’s surface.

• Artificial lakes: These are constructed for hydroelectric power generation, recreational purposes, industrial and agricultural use, and/or domestic water supply.

• The depth to which light can reach in lakes depends on turbidity or the amount and type of suspended particles in the water.

• The material at the bottom of a lake can be composed of a wide variety of

  • inorganic materials, such as silt or sand, and/or

  • organic materials, such as decaying plant or animal matter.

• Benthic Zone: The bottom of lake, organisms can tolerate cool temperatures and low oxygen levels.

• Limnetic Zone: A well-lit, open surface water, farther from shore, extends to a depth penetrated by light, occupied by phytoplankton, zooplankton, and higher animals; produces food and oxygen that supports most of a lake’s consumers

• Littoral Zone: It is shallow, close to shore, extends to depth penetrated by light; rooted and floating plants flourish

• Profundal Zone: It is deep, no-light regions, too dark for photosynthesis; low oxygen levels; inhabited by fish adapted to cool, dark waters

Wetlands:

• These are areas that are covered with water at some point in the year and that support aquatic plants.

• High plant productivity supports a rich diversity of animal life.

• The water found in wetlands can be saltwater, freshwater, or brackish

• Services:

  • Absorbing excess water from flooding or storm surges.

  • Acting as carbon sinks.

  • As sediment flows through a wetland from the surrounding watershed, it becomes trapped, reducing the siltation into lakes, rivers, and streams.

  • Providing areas for agriculture and timber

  • Providing recreational trees.

  • Recharging groundwater.

  • Serving as nurseries for fishes and shellfishes.

Rivers:

• The nutrient content of rivers and streams is largely determined by the terrain and vegetation of the area through which they flow and is also determined by adjacent and overhanging vegetation, the weathering of rocks in the area, and soil erosion.

• Rivers and streams move continuously in a single downhill direction, and their inputs include

  • groundwater recharge;

  • precipitation;

  • springs;

  • surface runoff; and

  • the release of stored water in ice and snowpack.

• Riparian Zone: These are lands adjacent to creeks, lakes, rivers, and streams that support vegetation dependent upon free water in the soil.

• Littoral Zone: the shallow area along the edge of a river where aquatic plants grow and aquatic animals live. It is the transition zone between the aquatic and terrestrial ecosystems.

Succession (Both primary and secondary)

Ecosystem services

• Cultural Benefits

  • Sustainable fisheries and aquaculture can directly support recreational services.

  • Recreational fishing is linked to healthy aquatic ecosystems.

• Provisioning Benefits

  • Ecosystems provide diversity of materials and products

  • Livestock provide different types of raw material such as fiber (wool), meat, milk

• Regulating Benefits

  • Keep pest populations in balance through natural predators.

  • Keeps food prices lower

  • Reduces the need for pesticides

  • Achieved in ecosystems through the actions of predators and parasites as well as by the defense mechanisms of their prey.

• Supporting Benefits

  • Form new soil and renew soil fertility

  • Allows for greater crop yields, which can feed more people.

  • Reduces the need for fertilizers.

Techniques for reducing erosion / Soil management techniques

1. No-till agriculture: This technique involves planting crops without disturbing the soil through tillage. Instead, a special planter is used to create a small hole in the soil where the seed is placed. This helps to reduce erosion, conserve moisture, and improve soil health.

2. Crop rotation: This technique involves planting different crops in a field each year to help maintain soil fertility and reduce the buildup of pests and diseases. For example, a farmer might plant corn one year, followed by soybeans the next year, and then wheat the year after that.

3. Cover cropping: This technique involves planting a crop, such as clover or rye, during the off-season to help protect the soil from erosion, improve soil health, and reduce weed growth. The cover crop is then tilled into the soil before planting the main crop.

4. Mulching: This technique involves covering the soil with a layer of organic material, such as straw or leaves, to help retain moisture, suppress weed growth, and improve soil health.

5. Composting: This technique involves collecting organic waste, such as food scraps and yard trimmings, and allowing it to decompose into a nutrient-rich soil amendment. The compost can then be added to the soil to improve soil health and fertility.

6. Terracing: This technique involves creating a series of level platforms on a steep slope to help reduce erosion and improve water retention. The terraces are typically built using stone walls or other materials to create a series of steps on the hillside.

El Nino, La Nina, and their effects

El Niño (Warm Phase)

• Air pressure patterns reverse direction, causing trade winds to decrease in strength.

• This causes the normal flow of water away from western South America to decrease “pile up.”

• As a result, the thermocline off western South America becomes deeper and there is a decrease in the upwelling of nutrients, which causes extensive fish kills.

• A band of warmer-than-average ocean water temperatures develops off the Pacific coast of South America.

• Effects are strongest during the Northern Hemisphere winter because ocean temperatures worldwide are at their warmest.

• Increased ocean warmth enhances convection, which then alters the jet stream

La Niña (Cool Phase)

• Trade winds that blow west across the tropical Pacific are stronger than normal.

• This then results in an increase in the upwelling off of South America.

• This then results in cooler-than-normal sea surface temperatures off of South America.

• This then results in wetter-than-normal conditions across the Pacific Northwest, and both drier- and warmer-than-normal conditions in the southern United States.

• This then results in an increase in the number of hurricanes.

• The southeastern US has warmer winters and the northwest cooler ones, while India and southeast Asia have heavier monsoons.

Types of soil particles

• Soil is a mixture of organic and inorganic matter, air, water, and minerals.

• The three primary types of soil particles are sand, silt, and clay.

  • Sand particles are the largest and have a gritty texture, good for drainage and aeration.

  • Silt particles are smaller and have a smooth, flour-like texture, good for holding moisture and nutrients.

  • Clay particles are the smallest and have a sticky, dense texture, good for retaining water and nutrients.

• The combination of these three particles determines the soil's texture and structure.

• Soil with a balanced mixture of all three particles is called loam soil, which is considered the ideal soil type for most plants.

Plate boundaries and examples

• Convergent Boundaries: These occur where two plates slide toward each other.

  • Commonly forming either:

    • a subduction zone, where one plate moves underneath the other; or

    • an orogenic belt, if the two plates collide and compress.

  • When a denser oceanic plate subducts a less dense continental plate, an oceanic trench may form on the ocean side and a mountain range on the continental side.

  • Ex.: Cascade Mountain Range

• Divergent Boundaries: These occur when two plates slide apart from each other.

  • It can create massive fault zones in the oceanic ridge system and areas of frequent oceanic earthquakes.

    • Examples:

      • Oceanic Divergent Boundary — Mid-Atlantic Ridge and the East Pacific Rise;

      • Continental Divergent Boundary — East African Great Rift Valley

  • When two oceanic plates converge, they create an island arc — a curved chain of volcanic islands rising from the deep seafloor and near a continent.

    • They are created by subduction processes and occur on the continental side of the subduction zone.

    • Their curve is generally convex toward the open ocean.

    • A deep undersea trench is located in front of such arcs where the descending plate dips downward.

  • When two continental plates collide, mountain ranges are created as the colliding crust is compressed and pushed upward.

• Transform boundaries: These occur where plates slide past each other in opposite directions.

  • The friction and stress buildup from the sliding plates frequently causes earthquakes, a common feature along transform boundaries.

  • Example: The San Andreas fault.

Integrated pest management

• IPM: It is an ecological pest-control strategy that uses a combination of biological, chemical, and physical methods together or in succession and requires an understanding of the ecology and life cycle of pests.

• Methods used in IPM include the following:

  • Construction of mechanical controls.

  • Developing genetically modified crops that are more pest-resistant.

  • Intercropping: A farming method that involves planting or growing more than one crop at the same time and on the same piece of land.

  • Natural insect predators

  • Planting pest-repellant crops

  • Polyculture: The simultaneous cultivation or raising of several crops or types of animals

  • Regular monitoring through visual inspection and traps followed by record keeping

  • Releasing sterilized insects

  • Rotating crops often to disrupt insect cycles

Types of irrigation

• Drip: Water is delivered at the root zone of a plant through small tubes that drip water at a measured rate.

• Flood: Water is pumped or brought to the fields and is allowed to flow along the ground among the crops.

  • Being simple and inexpensive, it is the method most widely used in less-developed countries.

• Furrow (Channel): Small parallel channels are dug along the field length in the direction of the predominant slope.

  • Water is applied to the top of each furrow and flows down the field under gravity, infiltrating the ground more at the beginning and less at the end.

• Spray: Uses overhead sprinklers, sprays or guns to spray water onto crops.

Different fuel sources (fossil fuels, nuclear, biomass, solar, geothermal, hydrogen, and wind)

• Fossil Fuels: Fuels formed from past geological remains of living organisms.

• Burning wood fuel: It creates the following by-products: carbon dioxide, heat, steam, water vapor, and wood ash.

• Peat: It is an accumulation of partially decayed vegetation or organic matter, mostly wetland vegetation like mosses, sedges, and shrubs, that forms in acidic and anaerobic conditions.

• Coal: Formed when dead plant matter that covered much of Earth’s tropical land surface at one time decays into peat and is then converted into coal by the heat and pressure of deep burial over millions of years.

  • Lignite: Often called brown coal, is the type most harmful to human health and is used almost exclusively as the primary fuel for electric power generation around the world.

  • Bituminous: Used primarily as fuel in steam-electric power generation.

  • Anthracite: Used primarily for residential and commercial space heating.

• Clean Coal: Technology that attempts to mitigate emissions of carbon dioxide and other greenhouse gases that arise from the burning of coal for electrical power.

  • Carbon capture and storage (CCS): Pumps and stores CO2 emissions underground.

• Natural gas: A fossil fuel formed when layers of buried plants and gases are exposed to intense heat and pressure over thousands of years.

• Oil: A fossil fuel produced by the decomposition of deeply buried organic material (plants) under high temperatures and pressure for millions of years.

• Cogeneration: Also known as combined heat and power (CHP), is an efficient technology to generate electricity and heat simultaneously at local facilities; otherwise, the heat produced from electricity generation is wasted.

• Solar energy: It consists of collecting and harnessing radiant energy from the sun to provide heat and/or electricity.

  • Electrical power and heat is generated at home and at industrial sites through photovoltaic cells, solar collectors, or at a central solar-thermal plant.

  • Passive solar heating: It does not include any type of mechanical heating device and functions by incorporating building features that absorb heat and then release it slowly to maintain the temperature throughout the building.

  • Active solar heating: It generates more heat than passive systems, and relies on three components: a solar collector to absorb the solar energy, a solar storage system, and a heat transfer system.

• Dams: These are built to trap water, which is then released and channeled through turbines that generate electricity.

  • Hydroelectric generation accounts for approximately 44% of renewable electricity generation, and 6.5% of total electricity generation in the United States.

  • There are about 75,000 dams in the United States that block ~600,000 miles (~1 million km) of what had once been free-flowing rivers.

• Geothermal: Heat contained in underground rock and fluids from molten rock (magma), hot dry-rock zones, and warm-rock reservoirs produces pockets of underground steam and hot water that can be used to drive turbines, which can then generate electricity.

• Hydrogen Fuel Cells:

  • The hydrogen fuel cell operates similarly to a battery with two electrodes—oxygen passes over one and hydrogen passes over the other.

  • The hydrogen reacts with a catalyst to form negatively charged electrons and positively charged hydrogen ions (H+).

• Wind:

  • Wind turbines work very simply: instead of using electricity to make wind—like a fan—wind turbines use wind to make electricity.

  • Wind turns the giant turbine blades, and then that motion powers generators.

  • Wind Farms: Wind turbines clustered together.

  • Using wind power is by far the most efficient method of producing electricity

  • One megawatt of wind energy can offset approximately 2,600 tons of CO2.

Those long lists of pollutants

Primary pollutants (especially the criteria pollutants)

• Carbon monoxide (CO): Health effects include headaches, dizziness, nausea, and death in high concentrations. Environmental effects include contributing to the formation of smog and acid rain.

• Nitrogen oxides (NOx): Health effects include respiratory problems and aggravation of asthma. Environmental effects include contributing to the formation of smog and acid rain.

• Sulfur dioxide (SO2): Health effects include respiratory problems and aggravation of asthma. Environmental effects include contributing to the formation of acid rain.

• Particulate matter (PM): Health effects include respiratory problems, heart disease, and lung cancer. Environmental effects include reducing visibility and contributing to climate change.

• Ozone (O3): Health effects include respiratory problems and aggravation of asthma. Environmental effects include contributing to the formation of smog and damage to crops and forests.

• Volatile organic compounds (VOCs): Health effects include respiratory problems and aggravation of asthma. Environmental effects include contributing to the formation of smog and damage to crops and forests.

• Carbon dioxide (CO2) is a colorless and odorless gas that is naturally present in the Earth's atmosphere. However, human activities such as burning fossil fuels and deforestation have significantly increased the levels of CO2 in the atmosphere, leading to negative health and environmental effects. High levels of CO2 can cause headaches, dizziness, and fatigue in humans, while also contributing to climate change and ocean acidification. Climate change can lead to extreme weather events, rising sea levels, and loss of biodiversity, while ocean acidification can harm marine life and disrupt entire ecosystems. Therefore, it is important to reduce our carbon footprint and find sustainable ways to mitigate the effects of CO2 emissions.

Secondary pollutants

1. Ozone (O3): Ozone is formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. It can cause respiratory problems such as coughing, wheezing, and shortness of breath. Long-term exposure to ozone can lead to reduced lung function and aggravate asthma and other lung diseases.

2. Photochemical smog is a type of air pollution that is formed when sunlight reacts with nitrogen oxides and volatile organic compounds emitted by vehicles, factories, and other sources. It is characterized by a brownish haze and can cause respiratory problems, eye irritation, and damage to crops.

   Industrial smog, on the other hand, is caused by the burning of coal and other fossil fuels in industrial processes. It is characterized by a grayish haze and can cause respiratory problems, heart disease, and lung cancer.

Indoor pollutants

• Carbon monoxide (CO): A colorless, odorless gas that can cause headaches, dizziness, nausea, and even death in high concentrations.

• Radon: A radioactive gas that can seep into homes from the ground and cause lung cancer.

• Volatile organic compounds (VOCs): Chemicals emitted from products like paints, cleaning supplies, and furniture that can cause eye, nose, and throat irritation, headaches, and even cancer.

• Particulate matter (PM): Tiny particles in the air that can cause respiratory problems, heart disease, and even premature death.

• Mold and mildew: Fungi that can grow in damp areas and cause allergic reactions, respiratory problems, and other health issues.

• Tobacco smoke: A mixture of chemicals that can cause lung cancer, heart disease, and other health problems.

• Asbestos: A mineral fiber that was once used in building materials and can cause lung cancer and other respiratory diseases.

• Lead: A toxic metal that can cause developmental problems in children and other health issues.

• Nitrogen dioxide (NO2): A gas that can cause respiratory problems, especially in people with asthma.

• Formaldehyde: A colorless gas that can cause eye, nose, and throat irritation, as well as cancer in high concentrations.

Thermal pollution

Thermal pollution is the harmful release of heated liquid or gas into the environment, which can have negative impacts on aquatic and terrestrial ecosystems. This type of pollution can occur when power plants and other industrial facilities use water for cooling purposes and then discharge the heated water back into nearby bodies of water. The increased temperature can reduce the amount of dissolved oxygen in the water, making it difficult for aquatic organisms to survive. It can also cause changes in the timing of biological events, such as the timing of fish spawning. Overall, thermal pollution can have significant ecological consequences and should be carefully managed to minimize its impacts.

Primary, secondary, and tertiary water treatment

Primary water treatment involves the physical removal of large solids and debris from the water. Secondary water treatment involves the biological removal of dissolved and suspended organic matter using microorganisms. Tertiary water treatment involves the removal of any remaining contaminants, such as nutrients and pathogens, through processes such as filtration and disinfection.

Cycles

Nitrogen

• Nitrogen makes up 78% of the atmosphere.

• The natural cycling of nitrogen, in which atmospheric nitrogen is converted to nitrogen oxides by lightning and deposited in the soil by rain, where it is assimilated by plants and either eaten by animals or decomposed back to elemental nitrogen by bacteria, includes the following processes:

  • Nitrogen Fixation: Atmospheric nitrogen is converted into ammonia (NH3) or nitrate ions (NO3–), which are biologically usable forms of nitrogen.

    • The key participants in nitrogen fixation are legumes, such as alfalfa, clover, and soybeans, and nitrogen-fixing bacteria known as Rhizobium.

  • Nitrification: Ammonia (NH3) is converted to nitrite (NO2–) and nitrate (NO3–), which are the most useful forms of nitrogen to plants.

  • Assimilation: Plants absorb ammonia (NH3), ammonium ions (NH4+), and nitrate ions (NO3–) through their roots.

  • Ammonification: Decomposing bacteria convert dead organisms and wastes, which include nitrates, uric acid, proteins, and nucleic acids, to ammonia (NH3) and ammonium ions (NH4+)—biologically useful forms.

  • Denitrification: Anaerobic bacteria convert ammonia into nitrites (NO2–), nitrates (NO3–), nitrogen gas (N2), and nitrous oxide (N2O) to continue the cycle

Phosphorous

• Phosphorus is essential for the production of nucleotides, ATP, fats in cell membranes, bones, teeth, and shells.

• Phosphorus is not found in the atmosphere; rather, the primary sink for phosphorus is in sedimentary rocks.

• Humans have impacted the phosphorus cycle in several ways, as follows:

  • Allowing runoff from feedlots, fertilizers, and municipal sewage plants to collect in lakes, streams, and ponds increases cyanobacteria, green algae, and aquatic plants.

    • This growth results in decreased oxygen content in the water, which then kills other aquatic organisms in the food web.

  • Applying phosphate-rich guano and other fertilizers containing phosphate to fields.

  • Clearing tropical habitats for farming, which reduces the amount of phosphorus that is readily available because it is contained in the vegetation.

  • Large-scale phosphorus-rich rock mining for inorganic fertilizers and detergents.

Carbon

• It is exchanged among the biosphere, geosphere, hydrosphere, and atmosphere and is the basic building block of life and the fundamental element found in carbohydrates, fats, proteins, and nucleic acids.

• The creation of coral reefs and the viability of externally fertilized egg cells are disrupted by ocean acidification caused by carbon dioxide absorption.

• Due to rising CO2 concentrations, oceanic acidity may slow the natural precipitation of calcium carbonate, reducing the ocean's capacity to absorb CO2.

• After the Industrial Revolution, the deforestation of old-growth forests and the combustion of fossil fuels released carbon stored in long-term carbon sinks, causing climate change and the following environmental impacts:

  • increased acidity of oceans

  • increase in atmospheric particulate matter

  • increased rate of melting of long-term water storage

  • stronger and more frequent storm events

Hydrologic

• Water cycle: It is powered by energy from the sun, which evaporates water from oceans, lakes, rivers, streams, soil, and vegetation.

• The oceans hold 97% of all water on the planet and are the source of 78% of all global precipitation.

• Oceans are also the source of 86% of all global evaporation, with evaporation from the sea surface keeping Earth from overheating.

• The water cycle is in a state of dynamic equilibrium by which the rate of evaporation equals the rate of precipitation.

  • Warm air holds more water vapor than cold air.

• Processes involved in the water cycle include the following:

  • Condensation: The conversion of a vapor or gas to a liquid

  • Evaporation: The process of turning from a liquid into vapor

  • Evapotranspiration: The process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants

  • Infiltration: The process by which water on the ground surface enters the soil

  • Precipitation: Rain, snow, sleet, or hail that falls to the ground

  • Runoff: Part of the water cycle that flows over land as surface water instead of being absorbed into groundwater or evaporating

NPP/GPP

NPP stands for Net Primary Productivity, which is the amount of carbon that is fixed by plants through photosynthesis, minus the amount that is lost through respiration. GPP stands for Gross Primary Productivity, which is the total amount of carbon that is fixed by plants through photosynthesis. In other words, NPP is the amount of carbon that is available for consumption by other organisms, while GPP is the total amount of carbon that is fixed by plants.

Age Structure Diagrams

Age structure diagrams are graphical representations of the distribution of different age groups in a population. There are three types of age structure diagrams: (1) pyramid-shaped/expansive, which indicates a rapidly growing population with a high birth rate and a high death rate; (2) column-shaped, which indicates a stable population with a relatively constant birth rate and death rate; and (3) inverted pyramid-shaped, which indicates a declining population with a low birth rate and a low death rate. These diagrams are useful for understanding population dynamics and predicting future population trends.

Permeability vs Porosity

Permeability refers to the ability of a soil to allow water or other fluids to pass through it. Porosity, on the other hand, refers to the amount of empty space or voids within a soil. A soil with high porosity will have more empty space for fluids to flow through, but if the soil particles are tightly packed, the permeability will be low. Conversely, a soil with low porosity will have less space for fluids to flow through, but if the soil particles are loosely packed, the permeability will be high. Therefore, permeability and porosity are related but not the same thing.

Types of air filters

• Baghouse filters: Fabric filters that can be used to reduce particulates.

• Burning pulverized coal at lower temperatures: Coal is crushed into a very fine powder and injected into a firebox.

• Coal gasification: A process that turns coal and other carbon-based fuels into gas known as “syngas.”

  • Impurities are removed from the syngas before it is combusted, which results in lower emissions of sulfur dioxide, particulates, and mercury.

• Cyclone separator: A method of removing particulates through rotational (spinning) effects and gravity.

• Electrostatic precipitator: A filtration device that removes fine particles, like dust and smoke, from a flowing gas using an electrostatic charge.

• Fluidized-bed combustion: A method of burning coal in which the amount of air required for combustion far exceeds that found in conventional burners.

  • This process can be used to reduce the amount of NOx, SOx, and particulates.

• Scrubbers: Systems that inject chemical(s) into a dirty exhaust stream to “wash out” acidic gases.

  • It can also be used to reduce SOx and particulates from burning coal.

• Sorbents: Activated charcoal, calcium compounds, or silicates can convert gaseous pollutants in smokestacks into compounds that baghouse filters, electrostatic precipitation, or scrubbers can collect.

Point source vs nonpoint source (although its fairly obvious)

• Point source air pollution: It occurs when the contaminant comes from an obvious source.

• Non-point source air pollution: It occurs when the contaminant comes from a source that is not easily identifiable or from a number of sources spread over a large, widespread area.