atmosphere
thin layer of gases that surrounds the earth
atmosphere composition
78% __________
21% oxygen
0.9% argon
0.1% water vapor, carbon dioxide, neon, helium and other trace gases
Troposphere
extends from the Earth’s surface up to about 10 km
It contains 75-80% of the atmosphere’s gases
Layer in which most weather occurs
Stratosphere
extends from 10 km to about 50 km above the Earth
contains the ozone layer which absorbs the majority of the ultraviolet radiation from the sun
Mesosphere
extends from 50 km to about 80 km above the Earth
The coldest layer of the atmosphere, dropping as low as –90o C
Thermosphere
extends from 80 km into outer space
The lower layer of the thermosphere is the ionosphere (80 km to 550 km) that can reflect radio waves back to Earth. It cannot reflect television waves, which have a shorter wavelength
The upper layer of the thermosphere is the exosphere, which extends for thousands of kilometers above the Earth, blending into the vacuum of interplanetary space
Air pollution
is the presence of one or more chemicals in the atmosphere in quantities and duration that cause harm to humans, other forms of life, and materials
Primary pollutants
Products of natural events and human activities
Secondary Pollutants
Some primary pollutants may react with one another or with the basic components of air to form new pollutants
Major Classes of Air Pollutants
Carbon Oxides (CO, CO2)
Sulfur Oxides (SO2, SO3)
Nitrogen Oxides (NO, N2O)
Volatile Organic Compounds – VOC’s (CH4, CFC’s)
Suspended Organic Particles (dust, soot, pesticides)
Photochemical Oxidants (O3, H2O2)
Radioactive Substances (radon-222, plutonium-239)
Toxic Compounds (mostly carcinogens)
photochemical smog
is formed when NOx and VOC’s react with heat and sunlight to produce a variety of pollutants.
industrial smog
consists mostly of sulfur dioxide formed from the burning of coal and heavy oil
catalytic converters
used in automobiles to convert CO, NOx and hydrocarbons to less harmful gases (like CO2)
Wet & Dry Scrubbers
gases in smokestakes are passed through CaO (lime) or CaCO3 (calcium carbonate) to remove SO2, accumulating in a sludge
Electrostatic Precipitators
removes particulates using an induced electric charge
Vapor Recovery Nozzle
on a gasoline pump minimized gas fumes from escaping
Afterburners
an additional combustion process
Acid Deposition
is the mixture of acidic rain, snow, fog, cloud vapor, and particles that reach the earth’s surface
Effects of acid depostion
direct damage to plant foliage, bark and roots
soil acidification and death of microorganisms
lake acidification and stress of aquatic life
sick-building syndrome
Buildings with particularly poor air quality (~17% of commercial buildings according to the EPA)
Causes of sick-building syndrome
may include the presence of tobacco smoke, formaldehyde, gasoline, radon gas, asbestos, carbon monoxide, VOCs and some species of fungi and bacteria
Exposure to air pollutants may lead to several human health issues
Lung cancer
Asthma – muscle spasms in the bronchial walls
Chronic bronchitis – inflammation of cells lining the bronchi and bronchioles
Emphysema – damage to air sacs in lungs
Radon-222
is a colorless, odorless, radioactive gas that is produced by the decay of uranium-238 in rocks and soil. The gas can seep upward through soil and accumulate in unventilated lower levels of buildings.
The U.S. Congress passed Clean Air Acts in 1970, 1977, and 1990, and impose the following strategies
EPA establishment of national ambient air quality standards (NAAQs)
EPA establishment of national emission standards for toxic air pollutants
Recent legislation, such as the “Clear Skies Initiative” (2003) have actually reduced the effectiveness of the Clean Air Act
Deficienies of Clean Air Acts
Continued reliance on pollution cleanup rather than prevention
Failure to sharply increase fuel efficiency standards for cars and light trucks
No requirement for stricter emission standards for fine particulates
Giving municipal trash incinerators 30-year permits
Weak standards for incinerators
Weak standards for emissions of CO2 and other greenhouse gases