Unit 7 MCQ Flashcards
What are the main pollutants released from coal combustion?
CO, CO2, SO2, NOx, particulate matter (PM), and toxic metals like mercury, arsenic, and lead
What are the health and environmental effects of SO2?
Respiratory irritant, worsens asthma and bronchitis, forms sulfurous smog, contributes to acid rain
What are primary pollutants?
Emitted directly from sources such as vechiles, power plants, factories, or nautral sources
What are secondary pollutants?
Primary pollutants that have transformed in presences of sunlight, water, O2
What did the Clean Air Act (1970) establish?
Getting rid of Lead from gasoline, required to have catalytic converts to reduce NOx, CO, and hyrdrocarbon emissions
What are the three key precursors to photochemical smog?
NO2, VOCs, and sunlight
How does NO2 contribute to smog formation?
Sunlight breaks NO2 into NO + O, and free O binds with O2 to form ozone (O3)
What are the main sources of VOCs?
Gasoline, formaldehyde, cleaning fluids, oil-based paints, coniferous trees
What conditions increase smog formation?
Higher temperatures, more vehicle traffic, increased VOC emissions, more sunlight
How does smog impact humans and the environment?
Humans: Respiratory irritant, worsens asthma/bronchitis, increases healthcare costs
Environment: Reduces sunlight, limits photosynthesis, damages plant stomata
How can smog be reduced?
Using public transportation, reducing vehicle emissions, increasing renewable energy sources, and implementing emission regulations
What is a thermal inversion?
A warm air layer traps cooler air (and pollutants) near the surface, preventing normal dispersion
What are the effects of thermal inversions?
Increased respiratory issues, decreased visibility, reduced tourism, decreased photosynthesis
What are common indoor air pollutants in developing vs. developed countries?
Developing: Biomass combustion (wood, manure, charcoal)
Developed: VOCs from furniture, cleaning supplies, and insulation
What is carbon monoxide (CO), and why is it dangerous?
A colorless, odorless gas that binds to hemoglobin, preventing oxygen transport (asphyxiant)
What is radon gas, and how does it enter homes?
Radioactive gas from uranium decay, seeps in through foundation cracks, can cause lung cancer
How does lead exposure occur indoors?
Old lead-based paint, lead pipes, inhaling lead dust, or drinking contaminated water
What technologies help reduce air pollution?
Vapor recovery nozzles: Capture gasoline fumes
Catalytic converters: Convert NOx and CO into less harmful gases
Electrostatic precipitators: Capture particulate matter
Scrubbers: Remove NOx, SO2, and VOCs
What pollutants cause acid rain?
Sulfur dioxide (SO2) and nitrogen oxides (NOx)
How does acid rain form?
SO2 and NOx react with oxygen and water to form sulfuric acid and nitric acid
What are the effects of acid rain?
Soil acidification, leaching of nutrients, toxic metal release (aluminum, mercury), aquatic species decline
How can acid rain be mitigated?
Using crushed limestone to neutralize acids, reducing SO2 and NOx emissions through scrubbers and renewable energy
What are major sources of noise pollution?
Construction, transportation, industrial activities, household noise
How does noise pollution impact wildlife?
Disrupts communication, migration, hunting, and predator-prey interactions
What are the effects of aquatic noise pollution?
Disrupts whale migration, damages hearing, interferes with mating calls
What is particulate matter (PM)?
Solid or liquid particles suspended in the air, also called ‘particulates’.
What are the two main sizes of particulate matter?
PM10 (particles <10 micrometers)
PM2.5 (particles <2.5 micrometers)
What is the difference between PM10 and PM2.5?
PM10 includes dust, pollen, and mold, too small to be filtered by nose hairs.
PM2.5 is smaller, comes from combustion, can travel deep into lungs, and is linked to lung disease.
What are common sources of particulate matter?
Natural sources:
* Volcanoes
* Forest fires
* Sea salt
* Dust storms
* Pollen
Human sources:
* Vehicle exhaust
* Industrial emissions
* Construction
* Coal combustion
How does PM affect human health?
Irritates respiratory system, worsens asthma, bronchitis, and COPD
Increases risk of lung disease and heart disease
PM2.5 can enter the bloodstream and cause systemic inflammation.
How does PM impact the environment?
Reduces visibility (haze)
Settles on plants, reducing photosynthesis
Can carry toxic metals and pollutants.
What technologies help reduce PM emissions?
Electrostatic precipitators: Use electric charge to capture PM
Baghouse filters: Fabric filters trap PM from industrial emissions
Scrubbers: Remove PM from exhaust using water or chemicals.
How can individuals reduce PM exposure?
Avoid outdoor activities during high PM levels
Use air purifiers indoors
Reduce use of wood stoves and fireplaces.
What are three main strategies to reduce air pollution emissions?
- Reduce fossil fuel use, 2. Improve technology, 3. Enforce regulations
How can we reduce vehicle emissions?
- Increase fuel efficiency (CAFE standards)
- Use public transportation, biking, carpooling
- Promote electric and hybrid vehicles
- Implement catalytic converters to reduce NOx and CO emissions
What is a catalytic converter, and how does it reduce emissions?
A device in vehicles that converts harmful gases (NOx, CO) into less harmful substances (N2, CO2, O2, H2O)
How do vapor recovery nozzles reduce pollution?
Capture gasoline vapors during refueling, reducing VOCs that contribute to smog
What are three major technologies used in power plants to reduce emissions?
- Electrostatic precipitators – Use electric charge to capture particulate matter
- Scrubbers – Remove SO2, NOx, and PM from emissions
- Baghouse filters – Fabric filters trap PM from industrial emissions
What is fluidized bed combustion, and how does it help?
A method that burns coal more efficiently at lower temperatures, reducing NOx emissions and improving fuel efficiency
How does crushed limestone reduce SO2 emissions?
Limestone (CaCO3) reacts with SO2 to form calcium sulfate, reducing acid rain formation
What does the Clean Air Act do?
Sets limits on six major air pollutants, requires monitoring, and enforces penalties for violations
What are CAFE standards, and how do they help?
Corporate Average Fuel Economy (CAFE) standards require vehicle manufacturers to make cars with higher fuel efficiency, reducing NOx, PM, and CO emissions
How do pollution credits work?
Companies that reduce emissions below EPA limits earn credits they can sell to higher-emission companies
What energy sources reduce air pollution?
- Renewable energy (solar, wind, hydro) emits no air pollutants
- Natural gas emits fewer pollutants than coal
- Nuclear energy produces electricity without emitting NOx, SO2, or CO2
What role do individuals play in reducing emissions?
- Conserve electricity by using energy-efficient appliances
- Reduce fossil fuel use by walking, biking, using public transportation
- Support policies that promote clean energy
What is the purpose of scrubbers?
Scrubbers are pollution control devices used in power plants and industrial facilities to remove SO2, NOx, VOCs, and particulate matter (PM) from emissions.
How do wet scrubbers work?
Water or chemical mist is sprayed into the exhaust stream. Pollutants like SO2, NOx, and PM dissolve or stick to water droplets. The polluted water droplets fall to the bottom and are collected for disposal.
What pollutants do wet scrubbers remove?
SO2, NOx, VOCs, and particulate matter (PM).
What are the advantages of wet scrubbers?
- Highly effective at removing SO2 and PM
- Can handle hot exhaust gases
- Helps reduce acid rain-causing emissions
What are the disadvantages of wet scrubbers?
- Produces wastewater that needs treatment
- High water consumption
- Can cause corrosion in the system
How do dry scrubbers work?
A dry chemical (calcium oxide or sodium bicarbonate) is injected into the exhaust. The chemical reacts with SO2, NOx, and VOCs to neutralize them. The neutralized pollutants turn into a dry powder, which is collected and disposed of.
What pollutants do dry scrubbers remove?
SO2, NOx, and VOCs.
What are the advantages of dry scrubbers?
- No wastewater production
- Lower water use than wet scrubbers
- Effective at reducing acid rain pollutants
What are the disadvantages of dry scrubbers?
- Not as effective at removing PM
- Produces solid waste that needs disposal
- Can be more expensive than wet scrubbers
What is the main difference between wet and dry scrubbers?
Wet scrubbers use liquid (water or chemicals) to trap pollutants. Dry scrubbers use dry chemicals to neutralize pollutants and form a solid byproduct.
Which type of scrubber is better for removing particulate matter (PM)?
Wet scrubbers are more effective at trapping PM in mist droplets.
Which type of scrubber is better for reducing water use?
Dry scrubbers because they do not produce wastewater.
What is the purpose of a catalytic converter?
A pollution control device in vehicles that reduces NOx, CO, and hydrocarbon emissions from exhaust gases.
How does a catalytic converter work?
Exhaust gases pass through a honeycomb structure coated with platinum, palladium, or rhodium. The metals catalyze chemical reactions that convert harmful gases into less harmful substances.
What pollutants do catalytic converters reduce?
Nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons.
What reactions occur inside a catalytic converter?
CO → CO₂ (Carbon monoxide is converted into carbon dioxide)
NOx → N₂ + O₂ (Nitrogen oxides are broken down into nitrogen and oxygen)
Unburned hydrocarbons → CO₂ + H₂O (Hydrocarbons combust into carbon dioxide and water)
Why are catalytic converters important for air quality?
They reduce smog formation by decreasing NOx emissions, which contribute to photochemical smog and acid rain.
Why was lead removed from gasoline?
Lead damaged catalytic converters, reducing their effectiveness. The EPA phased out leaded gasoline in 1974.
What are the benefits of catalytic converters?
Reduces harmful emissions
Helps meet Clean Air Act standards
Improves air quality in urban areas
What are the limitations of catalytic converters?
Do not remove CO₂, a greenhouse gas
Require unleaded fuel to function properly
Can be stolen due to valuable metals (platinum, palladium, rhodium)
What is ground-level ozone (O₃)?
A secondary pollutant formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in sunlight. It is a major component of photochemical smog.
How is ground-level ozone formed?
NO₂ (Nitrogen dioxide) absorbs sunlight and breaks into NO and O. The free O atom binds with O₂ to form ozone (O₃).
What are the main precursors to ground-level ozone?
NOx (nitrogen oxides) and VOCs (volatile organic compounds)
What are the major sources of NOx and VOCs?
NOx: Vehicle exhaust, industrial emissions, power plants
VOCs: Gasoline, cleaning products, oil-based paints, coniferous trees
When does ground-level ozone concentration peak?
Afternoon, especially on hot, sunny days, when sunlight intensity is highest.
What are the health effects of ground-level ozone?
Respiratory irritant – Worsens asthma, bronchitis, and COPD
Irritates eyes and throat
Reduces lung function and causes inflammation
How does ground-level ozone impact plants and ecosystems?
Damages plant stomata, reducing photosynthesis
Weakens crops and forests
Contributes to reduced agricultural yields
What is the difference between stratospheric and ground-level ozone?
Stratospheric ozone (‘good ozone’) protects Earth from UV radiation.
Ground-level ozone (‘bad ozone’) is a pollutant that harms health and the environment.
How can ground-level ozone pollution be reduced?
Reduce NOx and VOC emissions by using public transportation, electric vehicles, and renewable energy
Limit gasoline refueling and use low-VOC products
Follow ‘Ozone Action Days’ warnings and reduce outdoor activities when ozone levels are high
Why is ground-level ozone one of the fastest-forming pollutants that contributes to smog?
It forms quickly in sunlight when NO₂ breaks down, and its formation is accelerated by high temperatures and VOCs.
What role does NO₂ (nitrogen dioxide) play in ground-level ozone formation?
NO₂ absorbs sunlight and breaks into NO + O. The free O atom binds with O₂, forming ozone (O₃).
Why does smog form more quickly in urban areas?
High levels of NOx from vehicle emissions
More VOCs from gasoline, industry, and consumer products
Higher temperatures due to low albedo (Urban Heat Island Effect)
What time of day does ozone form the fastest?
Midday to afternoon, when sunlight is strongest and NO₂ emissions from morning traffic have reacted.
How do VOCs contribute to rapid smog formation?
VOCs react with NO to form photochemical oxidants, preventing NO from breaking down ozone, allowing O₃ levels to build up.
What factors make ozone levels spike in the summer?
More sunlight → Faster NO₂ breakdown
Higher temperatures → Speeds up chemical reactions
More evaporation of VOCs from gasoline and paints
What weather conditions slow down smog formation?
Cloudy days (less sunlight)
Rain (washes pollutants out of the air)
Wind (disperses pollutants)
Why is ozone a bigger problem in some cities than others?
Cities with high vehicle traffic, industrial activity, and warm climates experience the most ozone pollution.
How can we slow down ozone formation?
Reduce NOx emissions (cleaner vehicles, public transport)
Limit VOC emissions (low-VOC products, gas station vapor recovery)
Use renewable energy to reduce fossil fuel combustion
What is acid rain?
Precipitation (rain, snow, or fog) with a low pH due to sulfur dioxide (SO₂) and nitrogen oxides (NOx) reacting with water in the atmosphere.
What pollutants cause acid rain?
Sulfur dioxide (SO₂) and nitrogen oxides (NOx).
How does acid rain form?
SO₂ and NOx react with O₂ and H₂O in the atmosphere. They form sulfuric acid (H₂SO₄) and nitric acid (HNO₃). These acids dissolve in water and fall to the ground as acid precipitation.
What are the main sources of SO₂ and NOx emissions?
SO₂: Coal-fired power plants, metal smelting, burning diesel fuel
NOx: Vehicle emissions, industrial facilities, power plants
What are the environmental effects of acid rain?
Soil acidification – Removes nutrients (Ca²⁺, K⁺) from soil
Water acidification – Lowers pH of lakes and streams, harming aquatic life
Aluminum toxicity – Releases toxic metals that poison plants and animals
Forest damage – Weakens trees, reduces photosynthesis
How does acid rain impact aquatic life?
Lowers pH of lakes/rivers, making water too acidic for some species
Increases aluminum toxicity, which affects fish gills and blood chemistry
Leads to biodiversity loss as species die or migrate
How does acid rain affect human structures?
Corrodes buildings, bridges, and monuments, especially those made of limestone and marble
Damages metal structures and paint
What role does limestone play in neutralizing acid rain?
Calcium carbonate (CaCO₃) reacts with H⁺ ions, reducing acidity. Areas with limestone bedrock naturally buffer acid rain. Crushed limestone can be added to soil and lakes to neutralize acidity.
How can acid rain be reduced?
Reduce SO₂ and NOx emissions by using cleaner fuels
Use scrubbers in power plants to remove SO₂ from emissions
Increase renewable energy use (solar, wind, hydro)
Implement higher vehicle fuel efficiency standards (CAFE standards)
What is the largest source of acid rain in the U.S.?
The combustion of coal, which releases large amounts of sulfur dioxide (SO₂) and nitrogen oxides (NOx).
How does coal combustion contribute to acid rain?
Burning coal releases SO₂ and NOx into the atmosphere. These gases react with oxygen (O₂) and water (H₂O) to form sulfuric acid (H₂SO₄) and nitric acid (HNO₃). The acids dissolve in water and fall as acid rain.
What are the primary pollutants from coal combustion?
Sulfur dioxide (SO₂), nitrogen oxides (NOx), carbon dioxide (CO₂), and particulate matter (PM).
Why does the eastern U.S. experience more acid rain?
More coal-fired power plants in the Midwest and East. Winds carry SO₂ and NOx eastward, affecting forests and lakes. Fewer natural limestone buffers in some regions.
How does acid rain affect forests and lakes?
Soil acidification – Leaches away nutrients (Ca²⁺, K⁺). Water acidification – Lowers pH, harming fish and aquatic life. Increases aluminum toxicity, which damages plant roots and fish gills.
What technologies reduce SO₂ emissions from coal power plants?
Scrubbers – Use calcium carbonate (limestone) to remove SO₂.
Fluidized bed combustion – Burns coal at lower temperatures to reduce NOx.
Switching to low-sulfur coal – Reduces SO₂ emissions.
Transitioning to renewable energy – Solar, wind, hydro, and nuclear.
What law helped reduce acid rain in the U.S.?
The Clean Air Act (1970) – Set limits on SO₂ and NOx emissions from power plants.
How can acid rain be neutralized in lakes and soil?
Adding crushed limestone (CaCO₃), which reacts with H⁺ to raise pH.
What are the main environmental cons of power plants?
Air pollution – Releases SO₂, NOx, CO₂, and PM
Water pollution – Thermal pollution, heavy metal runoff
Habitat destruction – Deforestation, mining, land use changes
Resource depletion – Consumes nonrenewable fuels like coal, oil, and natural gas
What are the cons of coal-fired power plants?
High CO₂ emissions – Major contributor to climate change
Acid rain – Releases SO₂ and NOx, leading to acid precipitation
Health issues – Releases PM, mercury, and arsenic, causing respiratory diseases
Mining destruction – Coal mining destroys ecosystems and causes land subsidence
Produces toxic waste – Coal ash can contaminate water supplies
How do coal power plants contribute to acid rain?
They release SO₂ and NOx, which react with water to form sulfuric and nitric acid.
What are the cons of natural gas power plants?
Methane leaks – A powerful greenhouse gas
Still emits CO₂ – Though lower than coal, it contributes to global warming
Fracking impacts – Uses large amounts of water, causes earthquakes, and pollutes groundwater
What are the cons of nuclear power plants?
Radioactive waste – Spent fuel rods remain hazardous for thousands of years
Risk of accidents – Meltdowns (e.g., Chernobyl, Fukushima) can have catastrophic effects
High costs – Expensive to build and maintain
Thermal pollution – Heated water discharge can harm aquatic ecosystems
What is a major risk associated with nuclear energy?
Radioactive waste disposal and the potential for nuclear accidents.
What are the cons of hydroelectric power plants?
Disrupts ecosystems – Blocks fish migration, changes water flow
Flooding – Dams flood large areas, displacing communities and wildlife
Methane emissions – Decomposing vegetation in reservoirs releases greenhouse gases
Sediment buildup – Reduces river health and can lower dam efficiency
Why do hydroelectric dams impact fish populations?
They block migration routes, preventing species like salmon from reaching breeding grounds.
What are the cons of solar power plants?
Land use – Large-scale solar farms take up habitat space
Manufacturing impact – Producing panels requires mining and energy use
Intermittent energy – Doesn’t work at night and needs battery storage
What are the cons of wind power plants?
Bird and bat deaths – Turbines can kill flying animals
Noise pollution – Causes disturbances for nearby communities
Intermittent energy – Not reliable when wind is low
How can power plants reduce their environmental impact?
Switch to renewable energy – Solar, wind, hydro, nuclear
Use scrubbers and filters – Reduce SO₂, NOx, and PM emissions
Improve efficiency – Upgrade technology to reduce fuel use
Carbon capture – Store CO₂ underground to reduce emissions
