7.1 Introduction to Air Pollution (Pollutants)

  • Attribution: Modified from original creator Mr. Smedes

7.1.1 Suggested Skill 4.E

  • Scientific Experiments
    • Task: Explain modifications to an experimental procedure that will alter results.

7.1.2 Learning Objective and Knowledge (STB-2.A)

  • Objective: Identify the sources and effects of air pollutants.

  • Essential Knowledge:

    • STB-2.A.1: Coal combustion releases air pollutants including:

    • Carbon Dioxide (CO2)

    • Sulfur Dioxide (SO2)

    • Toxic metals

    • Particulates

    • STB-2.A.2: Combustion of fossil fuels releases nitrogen oxides into the atmosphere, which lead to:

    • Production of ozone (O3)

    • Formation of photochemical smog

    • Conversion to nitric acid (HNO3) in the atmosphere, causing acid rain.

    • Other pollutants produced: carbon monoxide (CO), hydrocarbons, particulate matter (PM).

    • STB-2.A.3: Air quality affected by the release of sulfur dioxide during the burning of fossil fuels, especially diesel fuels.

    • STB-2.A.4: Clean Air Act led by the Environmental Protection Agency (EPA):

    • Regulated lead, especially in fuels, reducing lead levels in the atmosphere significantly.

    • STB-2.A.5: Distinction between air pollutants:

    • Primary pollutants: Emitted directly from sources (e.g., vehicles, power plants).

    • Secondary pollutants: Formed through chemical reactions in the atmosphere.

7.1.3 Air Pollution Basics

  • Coal Combustion:

    • Responsible for 35% of global electricity; emits significant air pollutants:
    • CO, CO2, SO2, NOx, toxic metals (e.g., mercury, arsenic, lead), and PM.

  • Health Impact of SO2:

    • Acts as a respiratory irritant, worsening conditions like asthma and bronchitis.
    • Sulfur aerosols reduce visibility and photosynthesis.
    • Forms sulfurous (grey) smog.
    • Combines with atmospheric moisture and oxygen to form sulfuric acid leading to acid precipitation.

7.1.4 Nitrogen Oxides (NOx)

  • Release:

    • NOx comprises both NO and NO2, released primarily during combustion (fossil fuels and biomass).
    • NO forms when nitrogen (N2) combines with oxygen (O2) during high-temperature combustion, converting to NO2 through reactions with ozone or oxygen.
    • Sunlight can convert NO2 back to NO.

  • Environmental and Human Health Impacts:

    • Acts as a respiratory irritant.
    • Contributes to tropospheric ozone formation, leading to photochemical smog.
    • Combines with atmospheric moisture and oxygen to form nitric acid and contribute to acid precipitation.

7.1.5 EPA & Lead

  • Historic Context:

    • Prior to the Clean Air Act, lead was a common gasoline additive, phased out beginning in 1974 by the EPA.
    • Vehicles after 1974 must have catalytic converters to reduce emissions of NOx, CO, and hydrocarbons (note: lead contaminates these converters).

  • Neurotoxicity:

    • Lead is a known neurotoxin, particularly damaging to human nervous systems.

7.1.6 Air Pollutants - Primary vs Secondary

  • Primary Pollutants Include:

    • NOx, CO, CO2*, VOCs, SO2, PM, hydrocarbons.

  • Secondary Pollutants:

    • Tropospheric ozone (O3), sulfuric acid (H2SO4), sulfate (SO42-), nitric acid (HNO3), nitrate (NO3-).

  • Formation Dynamics:

    • Secondary pollutants tend to occur more frequently during daylight due to photosynthetic reactions driven by sunlight.

7.1.7 Exam Practice Question FRQ 7.1

  • Scenario: EPA scientists performed an experiment burning coal under various temperatures to analyze how temperature influences NOx emissions.
    • Question: Predict findings if the experiment is replicated using natural gas as opposed to coal.

7.2 Photochemical Smog

7.2.1 Learning Objective and Knowledge (STB-2.B)

  • Objective: Explain causes, effects of photochemical smog, and methods for reduction.

  • Essential Knowledge:

    • STB-2.B.1: Photochemical smog arises from nitrogen oxides and volatile organic compounds (VOCs) reacting under heat and sunlight to create various harmful pollutants.

    • STB-2.B.2: Environmental factors such as temperature, sunlight intensity, and emissions from vehicles foster photochemical smog formation.

    • STB-2.B.3: Nitrogen oxide production peaks in the morning, while ozone concentrations peak in the afternoon, particularly in summer months due to the abundant sunlight.

    • STB-2.B.4: VOCs evaporate or sublimate at room temperature. Common sources of VOCs include substances like formaldehyde and gasoline, as well as natural emissions from trees.

    • STB-2.B.5: Urban areas are especially prone to photochemical smog due to the high vehicle concentration.

7.2.2 Reduction of Photochemical Smog

  • Reducing nitrogen oxides and VOCs emission can diminish photochemical smog prevalence.
  • Health Impacts: Photochemical smog negatively affects human health, causing respiratory issues and eye irritation.

7.2.3 Formation Mechanism of Ozone

  • Process:
    • NO2 breaks down under sunlight into NO + O.
    • Free oxygen atom (O) binds with atmospheric O2 to create O3.
  • Conditions Favoring Formation:
    • Increased temperature accelerates evaporation of VOCs and interactions leading to smog formation.

7.2.4 Practice Question FRQ 7.2

  • Question: How does the time of day affect ozone formation?
    • Additionally, relate NO2 and ozone concentrations using a graph provided in the curriculum.

7.3 Thermal Inversion

7.3.1 Learning Objective and Knowledge (STB-2.C)

  • Objective: Describe thermal inversion and its pollution relationship.

  • Essential Knowledge:

    • STB-2.C.1: Thermal inversion alters atmospheric temperature gradients—cooler air exists at the earth's surface, trapped beneath warmer air above.

    • STB-2.C.2: This weather event traps pollution close to the ground, particularly smog and particulates.

7.3.2 Urban Heat Island Effect

  • Overview: Urban areas often exhibit elevated surface and air temperatures compared to surrounding areas due to:
    • Lower albedo: Materials like concrete and asphalt absorb more sunlight than vegetated areas.
    • Reduced evapotranspiration: Water from surfaces and plants carries heat into the atmosphere, cooling greener areas.

7.3.3 Effects of Thermal Inversion

  • During thermal inversion:
    • Pollutants such as smog, PM, and other compounds are trapped closer to Earth's surface.
    • Potential negative impacts include increased respiratory issues, reduced tourism, and decreased rates of photosynthesis.

7.3.4 Practice Question FRQ 7.3

  • Task: Explain the influence of thermal inversions on smog using diagrams provided.

7.4 Atmospheric CO2 and PM

7.4.1 Learning Objective and Knowledge (STB-2.D)

  • Objective: Describe natural sources of CO2 and particulates.

  • Essential Knowledge:

    • STB-2.D.1: CO2 is naturally generated from:

    • Respiration

    • Decomposition

    • Volcanic eruptions

    • STB-2.D.2: Numerous natural sources contribute to particulate matter emissions.

7.4.2 Natural Sources of Air Pollutants

  • Examples:

    • Lightning strikes convert atmospheric N2 into NOx.
    • Biomass combustion releases CO2 and water vapor.
    • Forest fires emit VOCs (e.g., terpenes, ethylene) contributing to natural photochemical smog.

  • PM Contributions:

    • Sources include: Sea salt, pollen, ash, and natural dust affecting visibility.

7.4.3 Indoor Air Pollutants

  • Size Comparison:

    • PM10: Particles <10 micrometers, can enter respiratory tract and contribute to chronic bronchitis.

    • PM2.5: Particles <2.5 micrometers, capable of penetrating deep into lungs and correlating with lung cancer risk.

7.4.4 Practice Question FRQ 7.4

  • Scenario: Students investigate how road construction affects surrounding PM levels by placing petri dishes coated with vaseline at various distances from a construction site and an active road.
    • Task: Identify the control group and the dependent variable of this experiment, along with measurement procedures.

7.5 Indoor Air Pollutants

7.5.1 Learning Objective and Knowledge (STB-2.E)

  • Objective: Identify indoor air pollutants.

  • Essential Knowledge:

    • STB-2.E.1: Carbon monoxide (CO) is recognized as an indoor air pollutant and asphyxiant.

    • STB-2.E.2: Particulates include asbestos, dust, and smoke.

    • STB-2.E.3: Indoor pollutants have various origins, both natural and human-made, often through combustion.

    • STB-2.E.4: Natural source pollutants include radon, mold, and dust.

    • STB-2.E.5: Human-made pollutants arise from various sources, including:

    • Insulation and VOCs from furniture

    • Formaldehyde from building materials

    • Lead from paints.

    • STB-2.E.6: Combustion pollutants include CO, nitrogen oxides (NOx), sulfur dioxide (SO2), particulate matter, and tobacco smoke.

7.5.2 Radon Gas and Health Impacts

  • Radon-222: A radioactive gas resulting from uranium decay in rocks, can infiltrate homes through soil and cracks. It contributes significantly to lung cancer rates in the U.S.
  • Health Risks: Exposure to radon correlates strongly with lung cancer; it is the second leading cause of lung cancer in America after smoking.

7.5.3 Developing vs. Developed Countries

  • Fuel Usage:

    • Developing nations utilize biomass fuels (wood, manure), releasing harmful pollutants (CO, PM, NOx, VOCs).
    • High indoor concentrations arise from poorly ventilated combustion, impacting health significantly.

  • Statistics: Approximately 3 billion people worldwide rely on subsistence fuels, accounting for an estimated 3.5 - 4.3 million annual deaths due to related indoor air pollution.

7.5.4 PM & Asbestos

  • Asbestos Danger: Long, silicate particles associated with lung cancer and diseases, previously used in insulation; now heavily regulated but still present in older buildings.

7.5.5 CO (Carbon Monoxide)

  • Source: Produced by incomplete combustion of any fuel in low oxygen conditions; poses severe health risks, often tied to malfunctioning appliances.

7.5.6 VOCs

  • Characteristics: Chemicals in many products that can easily vaporize and irritate respiratory tracts; sources include adhesives, cleaners, plastics, and fabrics.

7.5.7 Dust & Mold

  • Health Impact: Common indoor allergens causing respiratory aggravations like asthma; dust settles and can easily become airborne.

7.5.8 Lead

  • Risks: Found in older homes and can leach into water systems, primarily affecting children; removal requires certified professionals.

7.5.9 Practice Question FRQ 7.5

  • Task: Analyze the trend of confirmed blood lead levels in children over time.

7.6 Reduction of Air Pollutants

7.6.1 Learning Objective and Knowledge (STB-2.G)

  • Objective: Explore methods to reduce air pollutants at the source.

  • Essential Knowledge:

    • STB-2.G.1: Effective reduction strategies include regulatory practices, conservation efforts, and alternative fuels.

    • STB-2.G.2: Vapor recovery nozzles are devices preventing fuel fumes from escaping during refueling.

    • STB-2.G.3: Catalytic converters minimize harmful emissions from internal combustion engines.

    • STB-2.G.4: Scrubbers remove particulates and gases from industrial emissions.

    • STB-2.G.5: Additional technologies for coal power plants including scrubbers and electrostatic precipitators.

7.6.2 Practical Reduction Principles

  • Strategies such as reduced motor vehicle use, conserving energy, and promoting renewable energy sources help in diminishing air pollution.

7.6.3 Regulatory Framework

  • Clean Air Act: Empowers the EPA to regulate air quality, enforce limits on criteria pollutants, and monitor emissions.

7.6.4 Pollution Control Devices

  • Definitions of key devices and techniques for reducing emissions:
    • Vapor Recovery Nozzle: Captures vapors emitted during refueling to limit VOC pollution.
    • Catalytic Converter: Lowers emissions of NOx, CO, VOCs in vehicle exhaust.
    • Scrubbers: Remove sulfur oxides and particulates from exhaust, protecting air quality.

7.6.5 Practice Question FRQ 7.6

  • Task: Evaluate the Obama administration's CAFE standards effectiveness concerning NOx reduction based on provided data.

7.7 Acid Rain

7.7.1 Learning Objective and Knowledge (STB-2.H)

  • Objective: Define acid rain and deposition processes.

  • Essential Knowledge:

    • STB-2.H.1: Acid rain results from atmospheric nitrogen oxides and sulfur oxides.

    • STB-2.H.2: Major nitric oxides causing acid deposition largely stem from motor vehicles and coal power plants.

    • STB-2.1: Impacts of acid deposition on the environment include:

    • Acidification of soils and bodies of water.

    • Corrosion of man-made structures.

7.7.2 Limiting Acid Rain

  • Key methods include lowering emissions of NOx and SO2 through:
    • Enhanced CAFE standards.
    • Expanded public transit systems and the adoption of renewable energy.

7.7.3 Chemical Reactions Involved

  • Reactions:
    • NOx and SO2 react with atmospheric oxygen and water, forming nitric acid (HNO3) and sulfuric acid (H2SO4).
    • Both acids contribute to soil and water acidification.

7.7.4 Environmental Effects

  • Displacement of nutrients from soil due to H+ ions from acid rain adversely affects plant growth and aquatic life, leading to biodiversity loss.

7.7.5 Limiting Acid Rain through Neutralization

  • Limestone (CaCO3) used to neutralize acidic soils/waters, provides buffering in regions with limestone bedrock.