ATMOSPHERIC POLLUTION - 2020.pptx

Atmospheric Pollution

  • Overview of air pollution and its impacts.

Introduction to Air Pollution

  • Study focus: air pollution and related concepts.

What is Air Pollution?

  • Definition: Presence of harmful chemicals in the troposphere at high enough concentrations to alter climate.

  • Sources:

    • Natural Sources: Dust, wildfires, volcanic eruptions.

    • Human Sources: Combustion of fossil fuels.

  • Categories of outdoor air pollutants:

    • Primary Air Pollutants: Emitted directly into the atmosphere (e.g., SO₂, CO).

    • Secondary Air Pollutants: Created when primary pollutants react chemically (e.g., photochemical smog, H₂SO₄).

Air Pollution Basics

  • Fossil fuel combustion directly impacts air quality by releasing pollutants:

    • Includes VOCs, CO₂, SO₂, toxic metals, particulates, and nitrogen oxides.

  • Specifics of fossil fuel impacts:

    • Coal combustion releases high amounts of CO₂, SO₂, and particulates.

    • Leads to ground-level ozone, photochemical smog, and nitric acid (acid rain) formation.

    • Gasoline and diesel also emit significant SO₂.

Primary vs. Secondary Air Pollutants

Primary Air Pollutants

  • Definition: Harmful substances emitted directly into the atmosphere.

  • Examples:

    • Sulfur dioxide (SO₂)

    • Carbon monoxide (CO)

Secondary Air Pollutants

  • Definition: Formed from reactions of primary pollutants or other atmospheric components.

  • Examples:

    • Photochemical smog

    • Sulfuric acid (H₂SO₄)

The Clean Air Act

  • Established in 1970, with amendments in 1977 & 1990, enforced by the EPA to reduce air pollution levels.

  • EPA mandated to create National Ambient Air Quality Standards (NAAQS) for major pollutants:

    • Includes carbon monoxide, nitrogen oxides, sulfur dioxide, particulate matter, VOCs, ozone, and lead.

  • Results: Significant decrease in lead and other major pollutants in the atmosphere.

Major Air Pollutants

Carbon Oxides

  • Carbon monoxide (CO): Colorless, odorless, toxic gas from incomplete combustion.

    • Sources: Motor vehicle exhaust, fires, tobacco smoke.

  • Carbon dioxide (CO₂): Colorless, odorless gas, largely from natural sources but increasing due to human activity.

    • Unregulated under Clean Air Act despite rising concentrations.

Nitrogen Oxides

  • Nitrogen oxide (NO): Colorless gas formed at high temperatures in engines and power plants.

  • NO reacts to form nitrogen dioxide (NO₂): A reddish-brown irritant causing respiratory issues.

Other Nitrogenous Compounds

  • Nitric acid (HNO₃) and nitrate salts (NO₃⁻) from NO₂ reacting with water.

  • Contributes to acid rain and ecological damage.

  • Nitrous oxide (N₂O): Greenhouse gas from fertilizers and fossil fuel combustion.

Sulfur Compounds

  • Sulfur dioxide (SO₂): Colorless gas with a rotten egg smell.

    • One-third from natural sources, two-thirds from human activities (coal combustion, oil refining).

  • Forms sulfuric acid (H₂SO₄) and sulfates (SO₄²⁻) contributing to visibility reduction, health issues, and ecological harm.

Particulate Matter

  • Composed of small suspended solid particles.

    • Majority from natural sources (volcanic activity); human sources include vehicles.

    • Health effects: Respiratory issues, with toxic varieties causing severe health consequences.

Ozone

  • Ozone (O₃): Colorless, reactive gas; beneficial in the stratosphere but harmful at ground level.

    • Causes respiratory issues and damages vegetation.

Volatile Organic Compounds (VOCs)

  • Organic gases in the atmosphere.

    • Sources: Plant emissions, industrial solvents, vehicle emissions.

    • Long-term exposure linked to serious health risks like leukemia.

Radon

  • Radon-222: Odorless, colorless radioactive gas from rock/soil decay.

    • High concentrations can raise lung cancer risks, particularly in smokers.

Photochemical Smog

What is Photochemical Smog?

  • Formed when NOx and VOCs react with sunlight to create secondary pollutants.

  • Common in urban areas with heavy vehicle traffic, especially in warm, dry climates.

Photochemical Smog Formation

  • Environmental factors affecting smog creation:

    • Early nitrogen oxide production, ozone peaking in afternoon on hot days.

    • VOC emissions from traffic contribute to smog levels.

Impacts & Reduction of Photochemical Smog

  • Reducing NOx and VOCs key to combating smog.

  • Promoting mass transit can decrease pollutant emissions.

  • Health impacts include respiratory problems and eye irritation.

Thermal Inversion

What is a Thermal Inversion?

  • Normal temperature gradient disrupted: cooler air near the ground trapped under warmer air.

  • Creates pollution issues as pollutants remain concentrated at the surface.

Where do Thermal Inversions Occur?

  • Prone regions: Cities like Mexico City and Los Angeles due to geographical surroundings.

Atmospheric CO₂ & Particulates

Natural Sources of CO₂

  • Naturally present from respiration, decomposition, and volcanic eruptions.

Natural Sources of Particulates

  • Increases due to wildfires, volcanos, and pollination.

Indoor Air Pollutants

Indoor Air Pollution

  • Often more concentrated than outdoor pollution, posing health risks.

    • Major time spent indoors contributes to this.

Sources of Indoor Air Pollutants

  • Types:

    • Natural Sources: Radon, mold, dust.

    • Human-Made Sources: VOCs from furniture, formaldehyde.

    • Combustion: CO, NOx from various burning processes.

Radon-222

  • Naturally occurring gas, dangerous in high concentrations.

  • Can infiltrate homes through soil and groundwater sources.

  • Associated health risk: radon-induced lung cancer.

Reduction of Air Pollutants

How Can We Reduce Air Pollutants?

  • Recommended practices: Regulation, conservation, and alternative fuels.

  • Use of specific devices is crucial for major pollutant reduction.

Reducing Air Pollutants at the Gas Pump

  • Vapor recovery nozzles control gas fumes during refueling.

Reducing Air Pollutants from Cars

  • Catalytic converters minimize exhaust-related pollutants.

Reducing Air Pollutants from Power Plants & Industries

  • Wet and dry scrubbers help cleanse industrial emissions.

  • Electrostatic precipitators efficiently remove particulates but are energy-intensive.

Acid Deposition

What is Acid Deposition?

  • Known commonly as acid rain; results from NOx and SOx.

  • Combines with water to create acid products falling as precipitation.

Effects of Acid Deposition

  • Affects regions downwind from coal-burning facilities; can harm soil, water, and vegetation.

  • Areas with certain bedrock types may mitigate acid effects.

Continued Effects of Acid Deposition

  • Human health risks and structural corrosion (e.g., buildings, statues).

Noise & Light Pollution

What is Noise Pollution?

  • Sound at levels causing stress/harm; common urban sources include transportation and construction.

  • Ecological impacts on animals include stress and disrupted communication.

What is Light Pollution?

  • Artificial brightening of night skies altering natural behaviors and wasting energy.