Chapter 12

Air Pollution

1.    U.S. History (pg. 328)

·        Donora Pennsylvania (1948):  about 20 excess deaths.

·        High pressure system leads to stagnant air, radiation inversion in valley traps pollutants, which become deadly (pg. 346).  This combination of weather and topography is a  common theme in many air pollution problems.

·        Clean Air Act (1970):

·        Led to creation of U.S. EPA (clean water and clean air)

·        Focused on just six “criteria” pollutants

“Criteria” Pollutant

Chemical Formula

NAAQS Standard

Ozone

O3

0.075 ppm  (8 h)

Carbon monoxide

CO

9 ppm (8 h)

Sulfur dioxide

SO2

0.03 ppm  (annual)

Nitrogen dioxide

NO2

0.053 ppm  (annual)

Lead

Pb

1.5 micro g/ cu. m  (quarterly)

Particulate matter

PM10 and/or PM2.5

15 micro g/ cu. m  (annual)

 

·        Established National Ambient Air Quality Standards (NAAQS) for the criteria pollutants.

·        Air Quality Index (Table 12.2)

·        Primary pollutants – directly emitted from a source, e.g., carbon monoxide (from tail pipes).

·        Secondary pollutants – formed in the atmosphere by chemical reactions involving primary pollutants, e.g., ozone (from nitrogen dioxide, volatile hydrocarbons and sunlight).

2.    Tucson Air Quality

·        Air Info Now

3.    Sources

·        Table 12.1; Figure 12.2

·        Volatile organic carbon (VOC)

4.    Trends: it's getting better (Fig. 12.10)

5.    Meteorological Factors Affecting Air Pollution (pg. 340)

·        Winds  (Figure 12.13)

·        Inversions (Figure 12.14, 12.15, 12.16)

·        Topography (Figure 12.18)

6.    Acid Deposition (Fig. 12.21, 12.22, 12.23)

·        Sulfur dioxide (SO2) is oxidized to sulfuric acid (H2SO4)

·        Nitrogen dioxide (NO2) is oxidized to nitric acid (HNO3)

·        Both these acids return to earth as “dry deposition” or as “wet deposition”, i.e., in rain and fog.

·        On the east coast, where coal burning power plants generate both SO2 and NO2, sulfuric acid is often the dominant acid (about 3:1).

·        On the west coast, where little coal burning occurs, sulfuric acid and nitric acid occur in about equal concentrations (about 1:1).

·        EPA Acid Rain page

7.    Stratospheric Ozone

·        Stratospheric ozone occurs naturally.  It protects us from UV radiation and is the cause of the stratospheric inversion layer.  It accounts for 90% of all the ozone in the atmosphere, but is restricted to the stratosphere.

·        Manmade chemicals, especially Freons (chloroflorocarbons, CFCs), slowly migrate up into the stratosphere where they breakdown and generate catalysts that promote the rapid destruction of ozone.

·        The Antarctic ozone hole, a localized phenomenon that occurs only in the S. hemisphere Spring (starting in October) is the best example of stratospheric ozone depletion.  Global average ozone depletion is much harder to quantify.

·        NASA Total Ozone Mapping Spectrometer (TOMS) page

·        Cambridge University Ozone Hole Tour

·        EPA Stratospheric Ozone Depletion page