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.