Unit 7 Air Pollution

7.1: Introduction to Air Pollutants *STAR*

Air pollution refers to the presence of substances in the air that are harmful to human health or the environment.
Air pollutants can be primary or secondary. Primary pollutants are emitted directly from a source, while secondary pollutants form after primary pollutants interact with other substances in the air.
The burning of coal and fossil fuels releases pollutants such as carbon dioxide, sulfur dioxide, nitrogen oxides, and particulate matter.
Carbon monoxide, nitrogen oxides, sulfur dioxide, ammonia, volatile organic compounds, and particulate matter are examples of primary pollutants that can have serious health effects, including respiratory problems and cardiovascular disease.
Secondary pollutants include sulfur trioxide, sulfuric acid, nitric acid, ozone, and ammonium, which can contribute to the formation of particulate matter and acid rain.
Air quality is affected by the concentration of pollutants in the air and can have negative impacts on human health and the environment.

7.2: Photochemical Smog

Smog is derived from the combination of smoke and fog, and it was normally seen in industrial cities due to the use of coal and factory emissions.
The sulfurous emissions are called grey smog, while the type formed from the reaction of sunlight with pollutants in the air is called photochemical smog.
Photochemical smog is formed by the reaction of nitrogen oxides and volatile organic compounds (VOCs) with tropospheric ozone. *STAR*
It is most commonly found in urban areas with high levels of traffic and industrial activity and is typically more severe during the summer months when temperatures are higher and there is more sunlight.
Photochemical smog can have adverse effects on human health, including respiratory problems, and it can also damage plants and crops.
The pollutants that contribute to photochemical smog, including ozone and particulate matter, can have a range of negative effects on human health, such as irritations of the respiratory system and increased risks of cardiovascular disease.
It can also reduce crop yields and quality, which can have economic and social impacts.
It is important to reduce the levels of photochemical smog in the air to protect public health and the environment, which can be achieved through measures such as reducing vehicle emissions and increasing the use of renewable energy.

7.3: Thermal Inversion

Thermal inversion is a meteorological phenomenon where a layer of warm air becomes trapped above a layer of cooler air, creating a temperature reversal in the atmospheric temperature gradient.
Thermal inversions are caused by factors such as the movement of cold and warm air masses, the presence of high-pressure systems, and topographic features that trap warm air. *STAR*
They can occur at any time of year, but are more common during the winter months.
Thermal inversions can trap pollutants near the earth's surface, leading to poor air quality and reduced visibility. *STAR*
They can also prevent clouds from forming, leading to clear skies and increased solar radiation, and affect human health by increasing the risk of respiratory problems and making people feel uncomfortable.
Cities situated in valleys or surrounded by mountains are particularly susceptible to thermal inversion.
Thermal inversion can trap car exhaust fumes, industrial emissions, smoke from wildfires, and particulate matter from construction sites.
The relationship between thermal inversion and pollution trapping is complex and multifaceted, and understanding and predicting these inversions can help mitigate their impacts.

7.4: Atmospheric CO2 and Particulates

CO2 is a greenhouse gas released naturally and through human activities that traps heat from the sun, causing global warming and an increase in the Earth's average temperature.
Particulate matter (PM) is tiny particles suspended in the air from natural and human-made sources that can have serious health effects, especially for those with respiratory and cardiovascular conditions.
CO2 emissions from burning fossil fuels can release PM into the air, contributing to air pollution and health problems.
Climate change caused by high levels of CO2 in the atmosphere can lead to an increase in the frequency and severity of wildfires and dust storms, which can release large amounts of PM into the air.
Natural sources of air pollutants include volcanic eruptions, wildfires, dust storms, sea spray, biological processes, natural radioactivity, lightning strikes, forest fires, plants, and volcanoes.
Forest fires release PM, carbon monoxide, VOCs, greenhouse gases, and toxins into the air.
Plants release VOCs into the air during photosynthesis, which can react with other pollutants to form ground level ozone.
Volcanoes release ash, sulfur dioxide, and CO2 into the air, which can have negative impacts on human health and the environment.
All living organisms release CO2 as a byproduct of respiration.
Dust storms, volcanic eruptions, wildfires, sea spray, biological processes, and natural radioactive processes are natural sources of PM.
Aerobic decomposition is a natural source of CO2 and an important part of the global carbon cycle.
Anaerobic decomposition is a natural source of both methane and CO2.
Human activities such as burning fossil fuels, deforestation, and agriculture can disrupt natural decomposition processes, leading to an increase in CO2 and methane emissions, contributing to global warming and climate change.

7.5: Indoor Air Pollutants

Indoor air pollutants can come from sources such as tobacco smoke, building materials, household products, and outdoor air.
Carbon monoxide is a colorless, odorless gas produced by incomplete combustion, such as from a car or fireplace, and can cause asphyxiation.
Radon-222 is a radioactive gas found in the Earth's crust and can cause certain cancers if inhaled or ingested.
Volatile organic compounds (VOCs) are found in many household items, including formaldehyde in upholstery, furniture, and carpets.
Asbestos, commonly used in ceilings and insulation, can cause lung cancer if its small fibers are inhaled.
Sick Building Syndrome can occur when indoor pollutants are trapped due to lack of ventilation and can cause illness, such as from the buildup of ozone from copier machines.

7.6: Reduction of Air Pollutants

Air pollution reduction can be achieved through regulations, conservation, and alternative fuels.
The Kyoto Protocol and Paris Agreement are international agreements aimed at reducing greenhouse gas emissions and mitigating climate change.
Vapor Recovery Nozzles and catalytic converters are installed in vehicles to reduce the release of VOCs and toxic gasses into the air.
Industrial methods such as wet and dry scrubbers and electrostatic precipitators are used to remove pollutants from building exhausts and coal-burning power plants.
Conserving energy through carpooling, mass transit, and energy-efficient buildings can significantly reduce air pollution.
Laws such as the Clean Air Act, Montreal Protocol, Thematic Strategy on Air Pollution, and Beijing Action Plan have been implemented to address air pollution on a national and international level.

7.7: Acid Rain

Acid deposition occurs when NOX and sulfur dioxides are released to the atmosphere and react with ammonia gas, falling back to the ground as nitric salts and sulfates
Acid precipitation (acid rain/snow) occurs when NOX and SO2 undergo chemical reactions with water to form nitric acid and sulfuric acid
Acid rain affects both living and non-living things, damaging plant leaves, lowering soil pH, harming aquatic life, and dissolving rocks and statues
Mitigation of acid rain can be achieved by reducing emissions of SO2 and NOx, increasing efficiency of fossil fuel use, promoting renewable energy sources, planting vegetation, and using pollution control technologies like scrubbers