12-01 Title: The Atmosphere Caption: Diagram showing where each layer of the atmosphere is found. Notes: The ozone layer is in the stratosphere.

12-02 Title: The Nitrogen Cycle Caption: Fixation of nitrogen and its release back into the atmosphere. Notes: Plant and animal matter decay to replenish the nitrogen in the atmosphere.

12-03 Title: The Oxygen Cycle Caption: The fixation of oxygen and its release back into the atmosphere. Notes: Oxygen is converted to ozone in the stratosphere.

12-04a,b Title: Temperature Inversion Caption: Normal air temperature pattern (a) and a temperature inversion pattern (b). Notes: Air tends to get colder as the altitude increases.

12-05B Title: Smokestack Treatment Caption: One of the methods used to decrease air pollution caused by particulates in smokestacks. Notes: Air pollution is a major concern in our society.

12-05C Title: Electrostatic Precipitator Caption: One of the methods used to decrease air pollution caused by particulates in smokestacks. Notes: Air pollution impacts the economy.

12-05-01UN Title: Sources of Carbon Monoxide Caption: Pie chart showing the sources of carbon monoxide pollution. Notes: Transportation is the major contributor to CO pollution.

12-06 Title: CO and Hemoglobin Caption: Binding of carbon monoxide to iron in hemoglobin. Notes: Note that CO binds more strongly to hemoglobin than does oxygen.

12-08 Title: Air Pollution Caption: Graph showing air pollutant concentrations at different times of the day. Notes: Ozone pollution occurs later in the day.

12-09 Title: Acid Rain pH Caption: The position of acid rain on the pH scale. Notes: Acid rain has a pH below 5.6.

12-10 Title: Acid Rain Caption: Diagram illustrating the production of acid rain from human sources. Notes: Oxides of S and N are further oxidized.

12-12 Title: The Greenhouse Effect Caption: Diagram illustrating how the greenhouse effect occurs. Notes: Molecules absorb infrared energy.

12-13 Title: Global Warming Caption: Graph showing the increase in carbon dioxide concentrations over the past millennium. Notes: There has been a dramatic increase in carbon dioxide concentration during the 1900s.

12-14 Title: Average Surface Temperature Caption: Graph showing the changes in average surface temperature by year. Notes: A global warming effect can be seen after 1980.

12-14-02UN Title: Global Warming Project Caption: Graph for the Web Investigation on global warming. Notes: temperature changes during the past and next millennia

12-TB01 Title: Table 12.1 Clean Dry Air Composition Caption: Composition of clean air near sea level. Notes: Air is mostly nitrogen and oxygen.

12-TB02 Title: Table 12.2 Ozone Pollution Caption: Metropolitan areas ranked according to ozone pollution. Notes: Los Angeles leads all other cities in ozone pollution.

12-TB03 Title: Table 12.3 Air Quality Standards Caption: Pollution limits established for seven air pollutants. Notes: ppm = parts per million

12-TB04 Title: Table 12.4 Seven Major Air Pollutants Caption: Sources and effects of seven major air pollutants. Notes: Most pollutants are small inorganic molecules.