ENVIRON 102 Chapter Notes - Chapter 9: Cool Ground, Clear Skies Act Of 2003, Isotopes Of Radon

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Chapter 9: Air Quality (all)
9.1 Air Quality and Air Pollution
Air quality: amounts of gases and small particles in the atmosphere that influence ecosystems or
human well-being
Air pollution: gases and particles that are present in high enough concentrations to harm humans,
other organisms, or structures such as buildings or pieces of art
Earth’s atmosphere = nitrogen, oxygen, argon, and trace gases
Variable gases: concentration of these gases vary from time to time and place to place
o Ex: water, carbon dioxide, nitrogen oxides
o Concentrations of water vary by proximity to bodies of water, air temperature, and other
factors that influence the rate of evaporation
o Concentrations of carbon dioxide vary by daily/seasonal patterns of photosynthesis and
respiration and emissions of combusted fossil fuels
o Nitrogen oxides (NO, NO2, N2O) vary with the burning of fossil fuels
More in industrial and urban centers
Volatile organic compounds (VOC): organic chemicals that can vaporize into the air
o Ex: Methane most abundant, naturally occurring VOC
o Also found in anthropogenic source (solvents, paints, gasoline, and automobile exhaust)
Aerosols: suspended solid or liquid particles in the air
o Natural: the makeup of fog/clouds
o Human: pollutants that pose a health hazard
o Size of particle determines how long they stay in atmosphere and settle on surfaces
Sources of air pollution can be natural or human-caused
Primary air pollutants: chemicals or particles directly emitted from identifiable sources
o Ex: combustion and volcanic eruptions release elemental mercury
o Ex: burning of fossil fuels releases carbon monoxide and sulfur dioxide
o Ex: various industrial processes release CFCs (chlorofluorocarbons)
Secondary air pollutants: chemicals or particles that are produced in the atmosphere as a result of
reactions among chemicals or aerosols
o Ex: ozone is released by NO and O2 in the presence of sunlight
o Ex: urban smog = smoke + water droplets + mixture of chemicals
Photochemicals (aka photochemical aerosols): secondary pollutants formed with sunlight
A chemical can be both primary and secondary
Dispersion and Deposition of Air Pollution
Pollutants dispersed by diffusion, convection, and wind patterns
LOCALLY, gases and aerosols diffuse along concentration gradients and also through
convection/turbulence
o Ex: pavement heats air air rises rising air carries pollutants over cities and dilutes it
o Temperature inversion: when weather patterns cause a layer of warm air to form above
colder air
Usually occur on cold night when air underneath cool ground is trapped under
warm air air close to ground cannot mix with air above it
Ex: Donora, Pennsylvania
REGIONALLY, pollutants are dispersed by winds
o Ex: westerly winds of temperate regions & easterly winds of the tropics
GLOBALLY, convection cells in the troposphere disperse pollutants
Height of point sources affect the amount of pollutants in air near ground
o The higher, the more diluted/the more mixing
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