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layer of biosphere that contains gases

Atmospheric Pressure

force or mass per unit area of air; decreases as altitude and elevation increases


layer of atmosphere closest to earth's surface; where most of gases are found and weather


layer of atmosphere above troposphere; above the weather currents and contains ozone layer/shield that blocks harmful UV radiation


middle layer of atmosphere, the atmospheric layer between the stratosphere and the thermosphere


layer of atmosphere between mesosphere and exosphere; temperature increases as altitude increases


outermost laye of atmosphere; layer of the atmosphere that fades into outer space

Ozone Layer

found in stratosphere; composed of O3; blocks harmful UV radiation

Air Pollution

presence of chemicals or particles in the troposphere in concentrations high enough to harm organisms, ecosystems, or materials, and/or high enough to alter climate

Primary Pollutants

harmful substance emitted directly into the atomsphere; ex: sulfur oxides, nitrogen oxides, particulates

Secondary Pollutants

form when primary pollutants interact in the atmosphere with other pollutants or natural components of the atmosphere to form new harmful pollutants; ex: acid rain, sulfuric acid, nitric acid, surface-level ozone, PANs

Carbon Monoxide

CO; air pollutant that comes from incomplete combustion of any carbon containing fuel (especially fossil fuels); colorless and oderless gas that can react with hemoglobin in red blood cells and reduce ability of blood to circulate oxygen to cells and tissues

Carbon Dioxide

CO2; air pollutant that is not regulated by EPA under the Clean Air Act and comes from combustion of any carbon containing fuel (especially fossil fuels); acts as a greenhouse gas and can trap heat (infrared radiation) in atmosphere and lead to global climate change

Nitrogen Oxides

NO and NO2; air pollutant that often results from high temperature combusion of fossil fuels when nitrogen and oxygen gas in atmosphere react (commonly in automobile engines and coal-burning power plants); can react in atmosphere to create reddish/brown haze (NO2); can react in atmosphere with water vapor and form nitric acid (HNO3) and nitrate salts (NO3-) which can lead to acid rain and acid deposition

Sulfur Dioxide

SO2; colorless gas with irritating odor (rotten egg smell); can come naturally from sulfur cycle and volcanic activity; anthropogenic sources mostly include combustion of coal in power plants and oil refining process; can react in atmosphere with water vapor to form sulfuric acid (H2SO4) which leads to acid rain and acid deposition


suspended particulate matter (SPM); solid particles and liquid droplets light enough to remain suspended in atmosphere for short to long periods of time; sources: dust, wildfires, volcanic acitivity, sea salt, soot from combustion of coal, plowing fields, construction; can lead to greyish industrial smog and respiratory problems


beneficial in the stratosphere to block harmful UV radiation; harmful when it forms at surface-level due to interactions between vehicle emissions and sunlight; can cause respiratory problems and orange/brown haze called photochemical smog

Volatile Organic Compounds

VOC's; most are hydrocarbons (C3H8, C10H15) emitted naturally by leaves of plants or methane (CH4); can also come from benzene, vinyl chlorides, trichloroehylene, industrial solvents, dry-cleaning fluids, gasoline, plastics, synthetic rubber; can act as respiratory irritants, cause immune system damage, lead to formation of photochemical smog when they interact with sunlight and other chemicals


(Rn); naturally occurring colorless, oderless radioactive gas that comes from natural radioactive decay taking place in soil and rock; can seep into homes and buildings and cause lung cancer

Industrial Smog

typically greyish colored smog associated with industrial emissions of sulfur compounds and particulates; common in areas where high amounts of coal are burned (developing countries, developed countries during the industrial revolution)

Asian Brown Cloud

massive dark brown cloud of mostly industrial smog stretching nearly continuously across much of India, Bangladesh, industrial China, and the surrounding ocean; caused by combusion of coal, burning of forests for agricultural land, dust blowing off deserts in W. Asia

Photochemical Smog

often orangish / brownish color; forms as mixture of primary and seondary air pollutants under influence of heat and sunlight; VOC's + NOx + heat + sunlight = surface-level ozone, photochemical oxidants, peroxyacyl nitrates (PANs); common in areas that are sunny and have high vehicular traffic

Grasshopper Effect

volatile air pollutants like DDT, mercury, lead, polychlorinated biphenyls (PCBs) get transported via wind currents from tropical and temperate areas to the polar regions; explains why animals like polar bears, whales and sharks native to polar regions can still have high levels of these pollutants in their blood/tissues

Temperature Inversion

layer of warm air lays on top of cooler air near ground so dense cool air near surface does not rise and mix with air above it and pollutants concentrate in the stagnant layer of cool air near ground

Acid Deposition

usually caused by burning of fossil fuels and emissions of nitrogen oxides (high temperature burning of petroleum products and coal) and sulfur oxides (combustion of coal/diesel, oil refining) - nitrogen oxides mix to form nitric acid (HNO3) or nitrate salts (NO3-) and sulfur oxides mix to form sulfate salts (SO4-2) and sulfuric acid (H2SO4); dry particles or rain that have a pH below 5.6 - dry deposition usually happens in 2-3 days fairly close to the source of pollution; precipitation usually takes 4-14 days in more distant downwind areas

Sick-Building Syndrome

(SBS) when there is a strong link between air pollutants found in buildings and the number of health effects experienced by workers in that building; often caused by poor ventilation, mold, water damage to the structure, dust/particulates


indoor air pollutant; fireproof but cancer causing mineral that was widely used in older buildings for it insulating and fireproof characterisitcs; fibers become airborne and inhaled when damage is done to materials that contain asbestos and can lead to respiratory issues and lung cancer

Environmental Tobacco Smoke

ETS; also called second-hand smoke; indoor air pollutant that can cause respiratory issues and lung cancer


indoor air pollutnat; carcinogenic gas that has distinct odorand can be found in furniture, carpeting, upholstry fabrics, mattress padding, etc. very common industrial and commercial chemical and VOC used to make building materials and household products

Clean Air Act

passed in 1970 and amended in 1977 and 1990; federal gov't established air pollution regulation on point sources for key pollutants (carbon monoxide, nitrogen oxides, sulfur dioxide, particulates, VOC's, ozone, lead; not carbon dioxide) to be enforced by states and major cities; primary standards established to protect human health and secondary standards established to protect environment and property damage


National Ambient Air Quality Standards; establised for 6 outdoor air pollutants (carbon monoxide, nitrogen oxides, sulfur dioxide, VOCs, lead, ozone) due to the Clean Air Act

Primary Standards

specifies maximum allowable levels of 6 outdoor (ambient) air pollutants averaged over a specific time; to protect human health

Secondary Standards

specifies maximum allowable levels of 6 outdoor (ambient) air pollutants averaged over a specific time; to protect human health; to protect environment and human property


hazardous air pollutants; national emission standards are set for these by the EPA related to Clean Air Act; ex: chlorinated hydrocarbons, VOCs, toxic metals; Toxic Release Inventory (TRI) shows releases of HAPs above a certain minimum level from various industry, mining, etc.

Emissions Trading

allowed by the 1990 clean air act so that the 110 most polluting power plants can buy and sell SO2 pollution rights/credits

Electrostatic Precipitator

used to reduce particulates in smokestack emissions; particulates and soot discharged through smokestack are given a negative charge and pass by positively charged precipitator wall in the smokestack that attracts the particulates and soot and allows them to fall out of suspension and then be collected

Wet Scrubber

used to reduce particulates and SOx in smokestack emissions; fine mist is sprayed as emissions of particulates, soot and SOx pass by; fine mist traps particulates and soot and allows it to fall out of suspension and be collected; SOx passing through mist that has lime (CaO) or limestone (CaCO3) is converted to calcium sulfite (CaSO3) sludge that can be collected and disposed of

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