Intro to Air Pollution
Smog, Thermal Inversions, CO2 & PM
Indoor Air Pollutants
Reduction of Air Pollutants
Acid Rain & Noise Pollution
100
What is air pollution?
Describe how air pollution is a global problem.
What is the Clear Air Act of 1970?
- Air Pollution: The introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, materials (buildings) or ecosystems. Refers to pollutants in troposphere (AKA ground level pollution).
- Global: System with many inputs (cars, plants, or leaves that emit VOCs) & outputs (plant surfaces, soil, & atmospheric components). Air pollution can travel massive distances.
- Clean Air Act (1970): Legislators used info from environmental scientists & human health experts on what to monitor/control. Identified 6 criteria air pollutants (sulfur dioxide, nitrogen oxides, carbon monoxide, particulate matter, tropospheric ozone, & lead). Additional pollutants: carbon dioxide, mercury, & VOCS. Environmental Protection Agency (EPA) uses allowable concentrations to set criteria for whether air is “clean."
100
What is smog?
What are the two types of smog. Be able to describe both.
- Smog: Comes from combo of words smoke & fog. Responsible for hazy view & reduced sunlight. Leads to human health problems. Can also cause economic harm (i.e. - poor visibility in popular vacation destinations).
- Photochemical Smog: smog that is dominated by oxidants such as ozone. AKA: L.A.-type smog or brown smog.
- Industrial Smog: Smog dominated by sulfur dioxide, sulfate compounds, & particulate matter. AKA: London-type smog, gray smog, or industrial smog. Occurs where coal/oil is burned for electricity. SOx reacts with H20 → acid rain (H2SO4). Not a problem in most developed countries. Ex: Asian Brown Cloud - fly ash, black carbon, soot, & toxic chemicals.
- Photochemical vs. Industrial Smog: 
100
What is indoor air pollution?
Buildings are a closed system. How does this affect indoor air pollution accumulation?
- Indoor Air Pollution: Compounds that adversely affect the quality of air in buildings & structures.
- Building = closed system --> Traps pollutants indoors. Introduction and accumulation of pollutants affects health & comfort of occupants.
100
How can air pollution be controlled?
What are some regulatory practices that aim to lower air pollution?
- Controlled: Air pollution can be controlled by Conservation (using less fuel) & increasing fuel/energy efficiency, & Choosing alternative fuel (Includes cleaner burning fuels & alternative sources of energy).
- Regulatory Practices: Measures passed at all municipal levels to reduce air pollution. Include Requiring vapor recovery nozzles at all gas stations, Limiting evaporation of dry-cleaning fluids, Banning use of lighter fluid to start charcoal grills, Reduction in wood-burning stoves/fireplaces, Restricting automobile use, & Amendments to Clean Air Act.
100
What is pH?
What is the pH scale?
What is a base? What is an acid?
Why does water have a pH of 7?
Why is normal rainwater slightly acidic?
- pH: The relative strength of acids or hydrogen ions (H+) & bases or hydroxide ions (OH-) in a substance.
- pH Scale: Based on a logarithmic scale. Each # on scale represents a change by a factor of 10. Ex: 5 is 10x more acidic than a 6. Separates substances into basic (alkaline) or acidic
- Base: a substance that contributes hydroxide ions (OH-) to a solution.
- Acid: a substance that contributes hydrogen ions (H+) to a solution.
- Water: Neutral = 7. # of hydrogen ions (H+) = # of hydroxide ions (OH-).
- Rainwater: Reaction of rainwater & atmospheric CO2 → carbonic acid (H2CO3).
200
Be able to identify and describe the 6 primary air pollutants.
1. Sulfur Dioxide (SO2): A corrosive colorless, rotten smelling gas that comes primarily from combustion of fuels such as coal/oil, including diesel fuel from trucks. All organisms contain sulfur → fossil fuels derived from remains contain sulfur. Created when sulfur combines with oxygen during combustion. Released naturally during volcanic eruptions & forest fires. Respiratory & eye irritant & harmful to plant life. Leads to creation of industrial smog (combination of particulates & SO2 → smog) & acid rain (SO2 + H2O → H2SO4 (sulfuric acid).
2. Nitrogen Oxides (NOx): The creation of nitrogen oxide (NO: colorless, odorless gas) or nitrogen dioxide (NO2: pungent, reddish-brown gas) from the combustion of fossil fuels & biomass. Refers to either as they easily transform from one to the other in atmo. All combustion leads to formation of NOx (atmo = 78% N). Released naturally during forest fires, lightning, & microbial activity in soils. Respiratory irritant & harmful to plant life. Leads to creation of photochemical smog (NOx & VOCs react to sunlight → smog) & acid rain (NOx + H2O → HNO3 (nitric acid).
3. Carbon Monoxide: Carbon monoxide (CO): Colorless, odorless gas formed during incomplete combustion. Bonds to hemoglobin & hinders oxygen transport in blood. Significant air pollutant in urban areas with lots of vehicles/combustion, developed countries due to the malfunction of natural gas heaters, & developing countries due to combustion of biomass indoors.
4. Particulate Matter (PM): Solid or liquid particles suspended in air due to combustion of biomass & fossil fuels. Also formed from agricultural operations, unpaved roads, construction/demolition, etc. Naturally formed by production of sea spray & during volcanic eruptions, forest fires, & dust storms. Respiratory & eye irritant. Contributes to haze (reduced visibility) & decreased photosynthesis.
5. Ozone: Class of air pollutants formed as a result of sunlight acting on chemical compounds such as NOx & VOCs that contributes to formation of smog. Smog is a mixture of oxidants & particulates. Requires presence of SOx, NOx, & particulate matter (scatters light). Includes ozone (O3 or photochemical smog --> three oxygen molecules. Harmful to plants/animals, human respiratory function, & building materials.
6. Lead (Pb): A trace metal that occurs naturally in rocks/soils, is present in small concentrations in fuels (oil/coal), & is a neurotoxin. Released into air during combustion of gasoline & distributed in water & soils. Found in a variety of sources but mainly gasoline & paint. Phased out of gasoline U.S. starting in 1974 (completely by 1996). Phased out globally in 2021.
200
How does photochemical smog or ozone naturally form?
How is it naturally destroyed?
How does ozone accumulate to dangerous levels?
What factors affect ozone accumulation?
What are the health effects of photochemical smog?
- Ozone Formation: Requires sunlight (provides radiation & warms atmo), presence of nitrogen oxides (NO2), & few VOCS. Nitrogen dioxide (NO2) splits to form nitrogen oxide (NO). Energy from sun → free oxygen atom combines with diatomic oxygen (O2). Greatest accumulation during early/middle afternoon & in summer (light & warmth from Sun).
- Ozone Destruction: As sun intensity decreases (later in day) & NO is still present → ozone (O3) combines with nitrogen oxide (NO). Reforms into O2 + NO2. Occurs as UV radiation breaks down ozone (O3) into O & O2. Free oxygen atom bonds with NO → NO2.
- Ozone Accumulation: Requires high concentrations of VOCs (Strong smelling organic compounds that evaporate/sublimate at typical atmospheric temperatures. Many sources including spilling gasoline on pavement, combustion of fossil fuels --> releases formaldehyde [naturally occurring compound used as preservatives & adhesives], tree leaves in forests, & forest fires.) Hinders natural destruction of ozone. VOCs form strong bonds with NO. NO can no longer bond with O3 → breakdown of ozone doesn’t occur. Occurs commonly in urban areas in mid-afternoon (high density of cars releasing NO2 & VOCs). NO comes from exhaust from rush hour (7 a.m. - 9 a.m. & 5 p.m. to 8 p.m.).
- Factors: Increased atmospheric temps & longer days → higher emissions of VOCs & NOx → higher smog concentrations. More emissions of VOCs from vegetation & evaporation of gasoline. More emissions from fuel combustion (more air conditioning). More rapid chemical reactions → smog.
- Health Effects:
200
Be able to identify and describe various indoor air pollutants.
1. Carbon Monoxide (CO): Most dangerous → can cause asphyxiation. Binds to hemoglobin & hinders oxygen transport in blood. Leads to oxygen deprivation & death. Can come from urban outdoor air pollution that infiltrates a building or from within. Developed: malfunctioning exhaust system on household heaters. Developing: combustion of biomass with little to no mechanical ventilation (→ incomplete combustion).
2. Particulates (PM): Solid/liquid particles suspended in air. Includes smoke/soot (From indoor fires & smoking tobacco. Causes respiratory infections, bronchitis, cancer, etc.), dust (Combo of inputs to home environment. Includes PM, pollen, soil, bacteria, dead skin cells, droppings from dust mites (eat skin cells), dead insects, plastic fibers, clothing fibers, hair, etc. Contributes to asthma, & skin/respiratory allergies), & mold/mildew (Fungal growth that rapidly spreads on damp organic matter. Thrives in moist environments. Causes allergies, lung inflammation, & asthma).
3. Asbestos: A long, thin fibrous silicate mineral with insulating properties which can cause cancer when inhaled. Used for insulation on water pipes & in siding of buildings. Causes asbestosis (lung disease) & mesothelioma (lung cancer). Occur in high rates among asbestos miners. Not dangerous until disturbed. Fibers in insulating material can break off & become airborne. No longer used as an insulating material & must be professionally removed.
4. Radon-222: A colorless, odorless radioactive gas that occurs naturally in the decay of uranium & is an indoor air pollutant. Radon-222 decays to polonium-210 in 4 days. Attaches to dust/particles & is inhaled. Exists in granitic rocks/soils. Enters buildings through cracks in foundation or through groundwater in wells. Sealing cracks & radon mitigation systems reduce exposure. Leads to lung cancer. 2nd leading cause of lung cancer after smoking. Smoking worsens affects (synergistic reaction).
5. Volatile Organic Compounds (VOCs): Found in a variety of building materials, furniture, & home products. Possible routes of exposure: glues, paints, particle board, detergents, dry-cleaning fluids, construction materials, deodorizers, solvents, plastics, fabrics, synthetic carpets, & proximity to waste facilities or chemical plants. Ex: Formaldehyde (One of most toxic VOCs found in particle board & carpeting glue. Responsible for strong smells in newly constructed homes. Emits gasses over time & causes burning sensation in eyes/throat, trouble breathing, asthma, & possibly cancer). Can choose to use hardwood flooring/furniture or natural fiber carpeting to reduce exposure to VOCs.
6. Lead (Pb): Greatest source of lead indoors = leaded paint (Banned in 1978. Danger to inhabitants if lead paint begins to chip or is disturbed. Leads to particulate lead being ingested/inhaled). Lead from outdoors → indoors via air pollution & contaminated soils brought inside.
200
What is a vapor recovery nozzle?
What amendments were made to the Clean Air Act between 1990 & 1995? Understand Cap and Trade? Was it successful?
What is a catalytic converter? How does it work? Was it successful in lowering air pollution?
- Vapor Recovery Nozzle: A device that prevents VOCs from escaping into the atmo while a person is fueling their vehicle. Proposed in 1970s; fully adopted by 1990s. Captures 95% of vapors released when vehicles are being refueled.
- Amendments (1990 & 1995): Created market-based approach to limit SO2. Called Cap & Trade program. Instituted buying & selling of allowances to release a certain quantity of SO2. Allowances awarded annually & reduced over time. Not allowed to emit more sulfur than permitted (by allowances) → financial penalties. Successfully lowered emissions of SOx & NOx.
- Catalytic Converter: a device that uses chemicals to convert pollutants such as NO & CO to nitrogen gas and CO2. Uses a catalyst (typically transition metals) to increase rate of chemical reaction without itself undergoing change. Limits emissions of NO, CO, & hydrocarbons. Required addition to vehicle in 1975 as part of the Clean Air Act. Successfully lowered emissions of CO, NOx, & HCs.
200
What is acid rain? Understand what substances cause it and how it forms.
How is it transported?
What is the difference between wet and dry deposition?
What regulation exists that reduced emissions of NOx and SOx?
- Acid Rain: Precipitation high in sulfuric acid & nitric acid (AKA acid deposition). pH between 4.2 to 4.4. Generally anthropogenic but can be natural (volcanism). Occurs when SOx or NOx reacts with water vapor (H2O) in the atmosphere and forms sulfuric or nitric acid, respectively.
- Transported: Takes days + pollutants can travel 600+ miles by wind/atmospheric current before deposition (wet vs. dry).
- Regulation: Reduced in U.S. due to lower emissions of SOx & NOx. Result of Clean Air Act amendments of 1990 & 1995. Still a problem globally because it crosses international boundaries.
300
Be able to identify and describe minor air pollutants.
1. Mercury (Hg): Trace metal found in coal/oil & is toxic to central nervous systems of humans/other organisms. Released during burning of fossil fuels & waste incineration. Bioaccumulates in aquatic life.
2. Volatile Organic Compounds (VOCs): Organic compounds that evaporate at typical atmospheric temperatures, many of which are hydrocarbons. Compounds containing hydrogen-carbon bonds. Include plants, gasoline/fossil fuels, lighter fluid, dry-cleaning fluid, oil-based paints, & perfumes (strong smelling substances). Not always a result of combustion. Not necessarily hazardous BUT can lead to formation of photochemical smog.
3. Carbon Dioxide (CO2): Colorless, odorless gas formed during complete combustion. Not historically considered an air pollutant but is being reclassified due to increased emissions (fossil fuels) & global climate change. Absorbed by photosynthesis & released by respiration. Originally ONLY classified as a greenhouse gas, NOT an air pollutant because it doesn’t directly lower air quality & affect human health. Increases Earth’s temperature → harmful consequences for both humans & the environment. Contributes to ocean acidification. 2007 Supreme Court ruling allowed EPA to impose limits on harmful greenhouse gas emissions.
300
What is a thermal inversion?
- Thermal Inversion: An atmospheric condition in which a relatively warm layer of air at mid-altitude (inversion layer) covers a layer of cold, dense air below. Traps pollutants that accumulate beneath it close to ground → causes severe pollution events.
300
How does indoor air pollution compare in developing and developed countries?
- Developing: Comes mostly from indoor combustion of biomass. Can be ventilated but depends on quality of air outdoors.
- Developed: Has taken on greater importance in recent decades. People spend more time indoors. Improved insulation & tightly sealed buildings (for increased energy efficiency) trap pollutants indoors. Increased use of VOCs & petroleum-based products. Indoor air pollutant have greater effect on occupants.
300
What is a scrubber?
What is fluidized bed combustion?
What is a baghouse?
What is an electrostatic precipitator?
- Scrubber: A device used in factories & power plants that uses a combo of lime (dry) and/or water (wet) to remove particles from industrial exhaust streams. Separates/removes particles & sulfur dioxide. Particles/gases coalesce to form sludge & cleaner gas leaves through smokestack. Often relies on gravitational settling.
- Fluidized Bed Combustion: A scrubbing technique where granulated coal is burned close to calcium carbonate. Carbonate absorbs SO2 → calcium sulfate (used in production of wallboard & sheetrock).
- Baghouse: Air pollution control device that removes dust/particulate matter during industrial processes (AKA fabric filter). Used in coal power plants.
- Electrostatic Precipitator: A device that removes particulate matter by using an electrical charge to make particles coalesce so they can be removed from exhaust stream. Electrically charged particles are attracted to (+) or (-) & relatively clean gas exits.
300
How does acid rain affect terrestrial ecosystems?
How does acid rain affect aquatic ecosystems?
How does acid rain affect infrastructure?
How can acid rain be further mitigated?
- Terrestrial: Acidifies soil & inhibits plant growth. Decreases availability of nutrients. Leaches nutrients deeper into soil (below roots). Mobilizes toxic metals that can runoff into surface waters.
- Aquatic: Decrease species diversity. Affect food sources of aquatic organisms. Impair physiological functioning of organisms.
- Infrastructure: Can harm human-built structures like monuments, statues, & buildings. Corrodes metal & causes paint/stone to rapidly deteriorate.
- Mitigated: Reduce use of coal/oil. Use renewable energy. Remove pollutants from smokestacks/car exhaust (Scrubbers, electrostatic precipitators, catalytic converters, filters, etc.), Regulation (i.e. - Clean Air Act → capped emissions), Tax emissions, Using bases (like limestone) to neutralize affected areas.
400
How are air pollutants classified?
What is the difference between a primary and secondary pollutant?
- Classified: As primary vs. secondary & anthropogenic (man-made) vs natural.
- Primary Pollutants – emitted directly from a source (vehicles, forest fires, smokestacks, etc.) Include NOx, CO, CO2, SO2, & PM. Includes most VOCs (i.e. gasoline in uncombusted form from vehicles).
- Secondary Pollutants – primary pollutants that have transformed in the presence of sunlight, water, oxygen, or other compounds. Occurs more rapidly during the day & in wet environments. Includes O3, sulfuric acid, nitric acid, & carbonic acid.
400
What is urban heat island effect?
- Urban Heat Island: Urban areas experiencing higher temperatures than outlying areas. Often exacerbated at night (slow release of heat).
400
What is sick building syndrome?
- Sick Building Syndrome: A buildup of toxic pollutants in weatherized spaces, such as newer buildings in the developed world. EPA identifies 4 causes: Inadequate/faulty ventilation. Chemical contamination from indoor sources (i.e. - glues, carpeting, furniture, cleaning agents, & copy machines). Chemical contamination from outdoor sources (vehicle exhaust thru building intakes). Biological contamination from inside/outside (molds, pollen, etc.).
400
How can nitrogen oxides be removed from waste streams?
What are the consequences of this?
- NOx: Can be removed by lowering operating temperatures & controlling the amount of oxygen. Can lead to incomplete combustion →decreases efficiency & creates PM & CO. Use of technology can help regulate these processes.
400
What is ocean acidification? Understand how it happens.
500
How is the EPA related to air pollution?
What is the significance of the National Ambient Air Quality Standards?
- EPA: Monitors, regulates, & controls air pollutants & sources.
- NAAQS: National Ambient Air Quality Standards specifies concentration limits for air pollutants. Municipalities not in compliance subject to fines. All have decreased substantially in U.S. except for ozone.
500
How do natural processes affect the spread of air pollution?
What is particulate matter? What two types exist?
What are natural sources of carbon dioxide?
What are some natural sources of air pollutants?
- Natural Processes: Processes in nature produce and spread a variety of air pollutants. Effects of pollutants depend on natural conditions.
- Particulate Matter (PM): Ranges in size from 0.01µm to 100 µm. PM larger than 10 µm = filtered out by nose/throat. Can scatter sunlight and affect global temperature.
1. Particulate Matter-10 (PM10): Smaller than 10 µm. Not filtered out by nose/throat → can be deposited deep within respiratory tract.
2. Particulate Matter-2.5 (PM2.5): Particles of size 2.5 µm or smaller. Can travel further into respiratory tract (greater health concern). Often more toxic.
- Carbon Dioxide: Natural by-product of respiration, decomposition, & combustion.
1. Respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
Glucose + oxygen → carbon dioxide + water + energy
2. Decomposition
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (aerobic)
C6H12O6 → 3CO2 + 3CH4 + less energy (anaerobic)
3. Combustion
Fuel (often carbon-based) + O2 → CO2 + H2O
- Natural Sources:
500
What are some sources of outdoor air pollution?
What are some sources of indoor air pollution?
- Outdoor:
- Indoor:
500
What are the consequences of using devices to remove air pollution?
- Consequences: ALL air pollution control devices lower emission BUT Use more energy, Increase resistance to air flow, Use more fuel, & Result in higher CO2 emission.
500
What is noise pollution? Be able to list sources and effects of exposure.
What is the decibel scale?
How is noise pollution (and other pollution) related to environmental justice?
How does noise pollution affect wildlife?
How can noise pollution be mitigated?
- Noise Pollution: Unwanted sound that interferes with normal activities that is loud enough to cause health issues including hearing loss. Measured in loudness (decibels) & frequency (hertz). Can lead to hearing loss & other health problems. Includes Traffic, Construction, & Domestic/industrial activities. Exposure to noise Affects rent prices, Can differ between lower- & higher-income neighborhoods, & Is often worse in densely populated, congested areas.
- Decibel Scale: A logarithmic scale that measures both loudness & frequency. Can have max exposure for certain decibel levels.
- Environmental Justice: People of color, lower-income communities, & recent immigrants are more likely to live in proximity to Solid waste incinerators, Chemical production plants, Petroleum refineries, Toxic waste plants, Other industrial facilities. Experience worsened effects overall. Due to history of redlining.
- Wildlife: Causes stress & damages hearing. Reduces hunting efficiency (bats), Interferes with warning signals & mating calls (birds/amphibians), Alters migratory routes, & Interfere with underwater communication (whales).
- Mitigated: By enacting regulations that limit noise in sensitive areas.