Chapter 18 - Air Pollution

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