APES Unit 7

7.1 Introduction to Air Pollution

Air pollutants are released from various sources, including coal combustion and the burning of fossil fuels. The combustion of coal releases carbon dioxide, sulfur dioxide, toxic metals, and particulates, all of which contribute to pollution. Fossil fuel combustion, including the burning of diesel fuels, also emits nitrogen oxides that result in the formation of ozone and photochemical smog. In addition, these nitrogen oxides can transform into nitric acid, leading to acid rain. The release of other pollutants like carbon monoxide, hydrocarbons, and particulate matter is also a concern. Thanks to the Clean Air Act, the EPA regulated lead in fuels, reducing lead levels in the atmosphere significantly. Air pollutants are classified as either primary or secondary, depending on whether they are directly emitted or formed through chemical reactions in the atmosphere.

7.2 Photochemical Smog

Photochemical smog forms when nitrogen oxides and volatile organic compounds (VOCs) react with heat and sunlight, creating a variety of harmful pollutants. Nitrogen oxides are released early in the day, and ozone concentrations peak in the afternoon, particularly in summer when sunlight is more intense. VOCs, such as formaldehyde and gasoline, can evaporate or sublimate at room temperature, and trees also release these compounds naturally. Urban areas, due to the high volume of motor vehicles, are particularly prone to photochemical smog. The smog can harm human health, cuasing respiratory issues and eye irritation. Reduction of nitrogen oxides and VOCs can help mitigate the effects of photochemical smog.

7.3 Thermal Inversion

Thermal inversion occurs when the normal temperature gradient in the atmosphere is disrupted. In this case, the air near the Earth’s surface is cooler than the air above it. This inversion traps pollution near the ground, including smog and particulates, preventing them from dispersing into the atmosphere and leading to worsened air quality. 

7.4 Atmospheric CO₂ and Particulates

While often associated with human activities, carbon dioxide (CO2) and particulate matter also have natural resources. CO2 is naturally released into the atmosphere through respiration, decomposition, and volcanic eruptions. While these natural sources contribute to atmospheric CO2 particulate levels, human activities, particularly the burning of fossil fuels have significantly increased their concentrations, leading to climate change and air quality issues.

7.5 Indoor Air Pollutants

Indoor air pollutants can have a significant impact on health. Carbon monoxide, an asphyxiant, is one such pollutant. Other particulate pollutants include asbestos, dust, and smoke. Indoor pollutants come from both natural sources, such as radon and mold, and human-made sources, including insulation and VOCs from furniture and carpets. Formaldehyde, released from building materials and furniture, is another common indoor air pollutant. Radon, a naturally occurring radioactive gas from the decay of uranium, can infiltrate homes through basement and cracks, leading to lung cancer.

7.6 Reduction of Air Pollutants

There are several strategies for reducing air pollution, including regulatory practices, conservation practices, and alternative fuels. Regulatory practices, such as the Clean air act, set emission standards for vehicles and industries, and require the use of pollution control devices. Conservation practices, such as reducing energy consumption and using public transportation, can also help reduce air pollution. Alternative fuels, such as renewable energy sources and electrice vehicles, offer cleaner alternatives to fossil fuels. Additionally, technologies such as catalytic converters and scrubbers can be used to reduce emissions from vehicles and industrial processes. 

7.7 Acid Rain

Acid rain is caused by nitrogen oxides and sulfur oxides, which come from both natural and human-made sources. Nitrogen oxides are emitted by motor vehicles and coal-burning power plants, while sulfur dioxide primarily comes from coal burning power plants. The acid rain resulting from these pollutants has damaging effects on the enviroment. It can acidify soils and water bodies, harming aquatic life and damaging plants. The effects of acid deposition vary depending on regional soil composition, with areas containing limestone being better able to neutralize the acid. 

7.8 Noise Pollution (page 524)

Noise pollution is unwwanted or excessive sound that can have harmful effects on human health and the enviroment. Sources of noise pollution include transportation, construction, industrial activities , and even household appliances. Noise pollution can have hearing loss, stress, sleep disturbance, and other health problems. It can also disrupt wildlife communication and behavior, and even cause physical harm to animals. Efforts to reduce noise pollution include noise ordinancces, soundproofing , and the use of quieter technologies.