unit 7 apes notes

7.1 Introduction to Air Pollution (Pollutants)

The Clean Air Act (1970) represented a significant step in federal air quality legislation, identifying 6 criteria air pollutants that the EPA is tasked with setting limits for, monitoring, and enforcing regulations. These criteria air pollutants are crucial to understanding both human health impacts and environmental consequences.

Criteria Air Pollutants:

• SO2 (Sulfur Dioxide):

  • Source: Primarily generated from the combustion of coal and oil, particularly in energy production and industrial processes.

  • Health Effects: Acts as a respiratory irritant which can aggravate conditions such as asthma, and is a key contributor to smog and acid precipitation, affecting water sources and soil quality.

• NOx (Nitrogen Oxides):

  • Includes: Nitric oxide (NO) and nitrogen dioxide (NO2).

  • Source: Emitted during combustion processes, particularly fossil fuels used in vehicles and power plants.

  • Effects: Contributes significantly to the formation of ground-level ozone, creates photochemical smog, and leads to acid precipitation, which can harm ecosystems and infrastructure.

• CO (Carbon Monoxide):

  • Source: Produced by the incomplete combustion of fossil fuels in vehicles, homes, and industrial processes.

  • Health Effects: Lethal to humans at high levels; it interferes with the blood's ability to carry oxygen, leading to potential fatal outcomes, as well as being a respiratory irritant.

• PM (Particulate Matter):

  • Source: Generated from both fossil fuel combustion and biomass combustion, such as wood or crop burning.

  • Effects: PM can penetrate deep into the lungs and enter the bloodstream, causing severe respiratory issues and cardiovascular problems.

• O3 (Ozone, Tropospheric):

  • Source: Formed by photochemical reactions involving sunlight, NO2, and volatile organic compounds (VOCs).

  • Effects: Acts as a respiratory irritant, contributing to chronic respiratory diseases, and detrimental effects on plants and ecosystems.

• Pb (Lead):

  • Sources: Emissions from metal processing plants, battery manufacturers, and waste incineration facilities.

  • Health Effects: Recognized as a neurotoxicant, lead exposure can cause severe impairment to the nervous system, particularly in children, affecting development and cognitive function.

Primary vs. Secondary Air Pollutants:

• Primary Air Pollutants: These pollutants are directly emitted from identifiable sources. Common examples include NOx, CO, CO2, VOCs, SO2, PM, and hydrocarbons.

• Secondary Air Pollutants: These are not emitted directly; rather, they form in the atmosphere through chemical reactions involving primary pollutants. Notable secondary pollutants include tropospheric ozone (O3), sulfuric acid (H2SO4), and nitric acid (HNO3).

CO2:

Although carbon dioxide (CO2) is not classified as a criteria pollutant by the Clean Air Act, it is regulated as a greenhouse gas following the 2007 Supreme Court ruling. Its role in global warming and climate change is significant, given that human activities have drastically increased its levels in the atmosphere.

7.2 Nitrogen Oxides (NOx)

Formation and Transformation:

Nitric oxide (NO) is produced when nitrogen (N2) reacts with oxygen (O2) during high-temperature combustion processes. NO can further convert to nitrogen dioxide (NO2) by reacting with ozone (O3) or dioxygen (O2), and the presence of sunlight can convert NO2 back to NO, perpetuating pollution cycles.

Environmental and Human Health Impacts:

Exposure to NOx is a respiratory irritant and exacerbates conditions such as asthma. It also plays a significant role in the formation of ground-level ozone and contributes to acid precipitation, both of which can harm human health, biodiversity, and weather patterns.

7.3 Photochemical Smog

Precursors and Conditions for Formation:

Nitrogen oxides (NOx) and volatile organic compounds (VOCs) serve as critical precursors to photochemical smog formation. Sunlight promotes the breakdown of NO2, which in turn leads to the formation of ozone. Conditions such as high temperatures and stagnant air are conducive for smog development.

Sources of VOCs:

• Common Sources: Gasoline, formaldehyde, many household cleaning products, and industrial solvents.

• Emission Dynamics: VOCs are prevalent in urban areas due to emissions from traffic, industrial operations, and the usage of consumer products, leading to heightened pollution levels and health risks for urban populations.

7.4 Atmospheric CO2 & Particulate Matter (PM)

Natural Sources of Air Pollutants:

• Lighting Strikes: Convert atmospheric nitrogen (N2) into nitrogen oxides (NOx).

• Forest Fires: Release a combination of carbon monoxide (CO), particulate matter (PM), and nitrogen oxides (NOx), contributing to atmospheric pollution.

• Volcanic Eruptions: Emit sulfur dioxide (SO2), particulate matter, CO, and NOx, affecting air quality over broad areas.

Types of PM:

• PM10: Particles less than 10 micrometers in diameter; these can irritate the respiratory tracts and lead to various health issues.

• PM2.5: Finer particles less than 2.5 micrometers; these can penetrate deep into the lungs and have been associated with chronic respiratory diseases, cardiovascular problems, and premature death.

7.5 Indoor Air Pollutants

Developing Nations:

The reliance on biomass fuels such as wood and charcoal results in high levels of carbon monoxide (CO) and PM emissions indoors. Poor ventilation exacerbates these emissions, leading to serious health risks and contributing to millions of deaths annually from respiratory illnesses.

Developed Nations:

Common indoor pollutants include chemicals in household products (e.g., adhesives, cleaning agents) as well as particulate matter and dust. Historically, issues linked to lead paint (banned in 1978) and asbestos exposure have raised significant health concerns, necessitating regulations for safer indoor environments.

7.6 Reduction of Air Pollutants

Emission Reduction Strategies:

• Encouragement of public transportation, biking, and walking to minimize vehicle emissions.

• Implementation of energy conservation measures, promotion of renewable energy sources, and stringent regulations provided by the Clean Air Act to curb emissions.

7.7 Sources of Acid Rain

Major Pollutants:

The primary contributors to acid rain are nitrogen oxides (NOx) and sulfur dioxide (SO2), primarily sourced from coal-fired power plants and vehicle emissions. These pollutants react in the atmosphere to form acids that precipitate as acid rain, impacting soil, water sources, and vegetation.

7.8 Environmental Effects of Acid Rain

Soil and Water:

Acid rain results in the leaching of essential nutrients from the soil and increases the solubility of toxic metals, which can lead to devastating effects on plant life and aquatic ecosystems. Disruptions in pH levels can adversely affect aquatic life, driving population declines.

7.9 Noise Pollution

Sources:

Major contributors to noise pollution include construction activities, transportation systems (cars, trains, planes), and industrial operations. Domestic noise, such as that from home appliances and lawn equipment, compounds the overall levels of noise pollution.

Effects on Human and Wildlife:

Noise pollution can lead to profound physiological stress in humans and wildlife, impairing communication among species and contributing to population declines. Long-term exposure can lead to chronic health issues, such as cardiovascular disease and anxiety disorders for humans.