Glossary
Acid Rain
Rain or any other form of precipitation that is unusually acidic, primarily caused by emissions of sulfur dioxide and nitrogen oxides into the atmosphere.
Example:
Forests in the northeastern United States have suffered damage from acid rain caused by industrial emissions from the Midwest.
Aerobic Decomposition
The breakdown of organic matter by microorganisms in the presence of oxygen, primarily releasing carbon dioxide.
Example:
Composting relies on aerobic decomposition to break down food scraps and yard waste into nutrient-rich soil.
Anaerobic Decomposition
The breakdown of organic matter by microorganisms in the absence of oxygen, producing methane and carbon dioxide.
Example:
Landfills are significant sources of methane due to the anaerobic decomposition of buried organic waste.
Biological Processes (as pollutant source)
Natural activities of living organisms that can release air pollutants, such as methane from wetlands.
Example:
The decomposition of organic matter in swamps through biological processes naturally releases methane into the atmosphere.
Carbon Cycle
The biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.
Example:
Photosynthesis and respiration are key processes in the carbon cycle, balancing CO2 levels in the atmosphere.
Carbon Dioxide (CO2)
A major greenhouse gas that traps heat in the Earth's atmosphere, contributing to global warming.
Example:
The burning of fossil fuels for electricity generation releases significant amounts of CO2 into the atmosphere.
Carbon Monoxide (CO)
A colorless, odorless, and highly toxic gas produced by the incomplete combustion of carbon-containing fuels.
Example:
Faulty furnaces or car exhaust in enclosed spaces can lead to dangerous levels of carbon monoxide poisoning.
Dust Storms
Natural phenomena where strong winds lift large quantities of dust and sand from dry regions into the atmosphere.
Example:
A massive dust storm in the Sahara Desert can transport fine particulate matter across the Atlantic Ocean to the Americas.
Global Warming
The long-term heating of Earth's climate system observed since the pre-industrial period, primarily due to human activities that increase greenhouse gas concentrations.
Example:
Scientists are concerned that continued global warming could lead to more frequent and intense heatwaves.
Greenhouse Gas
Gases in Earth's atmosphere that trap heat, preventing it from escaping into space and thus warming the planet.
Example:
Methane is a potent greenhouse gas that contributes significantly to atmospheric warming, even though it is less abundant than CO2.
Ground-level ozone
A harmful air pollutant and component of smog, formed when nitrogen oxides and volatile organic compounds react in the presence of sunlight.
Example:
Exercising outdoors on a high ground-level ozone day can be detrimental to respiratory health.
Isoprene
A common volatile organic compound naturally emitted by many plants, contributing to atmospheric chemistry and ozone formation.
Example:
The blue haze often seen over forested mountains is partly due to the atmospheric reactions of isoprene released by trees.
Methane (CH4)
A potent greenhouse gas, much more effective at trapping heat than CO2 over a shorter timescale, produced by anaerobic decomposition.
Example:
Rice paddies are a source of atmospheric methane because the flooded conditions create an anaerobic environment for decomposition.
Methanol
A simple alcohol that is a volatile organic compound, naturally emitted by plants and also used in industrial processes.
Example:
Some plants release methanol as a byproduct of their metabolic processes, contributing to atmospheric VOCs.
Natural Radioactivity
The spontaneous emission of radiation from unstable atomic nuclei found in rocks and minerals, releasing radioactive particles into the environment.
Example:
Radon gas, a product of natural radioactivity from uranium in soil, can accumulate in homes and pose a health risk.
Natural Respiration
The biological process by which living organisms convert organic matter into energy, releasing carbon dioxide as a byproduct.
Example:
Both animals and plants undergo natural respiration, contributing to the constant exchange of CO2 in the atmosphere.
Nitrogen oxides (NOx)
A group of highly reactive gases containing nitrogen and oxygen, formed during high-temperature combustion or natural processes like lightning.
Example:
Vehicle exhaust is a major source of NOx in urban areas, contributing to smog formation.
Particulate Matter (PM)
Tiny solid or liquid particles suspended in the air, originating from natural sources like dust storms or human activities like burning.
Example:
During a large wildfire, the air becomes thick with particulate matter, making it difficult to breathe and reducing visibility.
Sea Spray
Fine particles of salt and other substances released into the atmosphere from ocean waves breaking and evaporating.
Example:
The salty air near coastal regions is often due to sea spray carrying tiny salt particles inland.
Smog
A type of air pollution formed when sunlight reacts with nitrogen oxides and volatile organic compounds, creating ground-level ozone and other pollutants.
Example:
On hot, sunny days in large cities, the hazy brown layer visible in the air is often smog.
Sulfur dioxide (SO2)
A colorless gas with a pungent odor, released naturally by volcanoes and anthropogenically by burning fossil fuels, contributing to acid rain.
Example:
Large industrial power plants often emit sulfur dioxide as a byproduct of burning coal, requiring scrubbers to reduce pollution.
Terpenes
A large class of volatile organic compounds produced by a wide variety of plants, contributing to their scent and atmospheric reactions.
Example:
The distinctive aroma of citrus fruits comes from various terpenes found in their peels.
The Greenhouse Effect
The natural process by which certain gases in Earth's atmosphere trap heat, warming the planet's surface and lower atmosphere.
Example:
Without the Greenhouse Effect, Earth's average temperature would be too cold to support most life.
Toxins (Dioxins, Furans, PAHs)
Highly poisonous chemical compounds, often byproducts of combustion processes like wildfires, that can harm human health and the environment.
Example:
Exposure to toxins like dioxins released from burning plastics can have severe long-term health consequences.
Volatile Organic Compounds (VOCs)
Organic chemicals that have a high vapor pressure at room temperature, easily evaporating into the atmosphere and contributing to air pollution.
Example:
The distinct smell of pine forests comes from naturally emitted VOCs like terpenes from trees.
Volcanic Eruptions
Natural events where molten rock, ash, and gases are expelled from a volcano, releasing various air pollutants.
Example:
A major volcanic eruption can inject large quantities of sulfur dioxide and ash high into the atmosphere, affecting global climate and air quality.
Wildfires
Uncontrolled fires that burn in wildland areas, releasing significant amounts of particulate matter, carbon monoxide, and greenhouse gases.
Example:
Intense wildfires in California often lead to widespread smoke plumes that impact air quality hundreds of miles away.