Environmental Engineering Reference
In-Depth Information
8.4.6.7  Radioactive Compounds
Radioactive compounds occur naturally, with the most common being radon. Radon is
produced from the decay of uranium (ATSDR 2008c) and is present in air, water, and
soil. Radon may build up in basements, especially if cracks exist, or other subsurface
structures located above natural deposits having higher relative uranium levels. The
half-life of radon is approximately 4 days (ATSDR 2008c). Most of the human exposure
attributed to other radioactive compounds results from medical devices, diagnostic
treatments, testing equipment such as x-ray machines, and cancer therapy (Kathren
1991; ATSDR 2000).
8.4.6.8  Greenhouse Gases
Greenhouse gases decay very slowly and are primarily atmospheric contaminants. Some
quantities of these gases are naturally removed from the atmosphere, such as the removal
of carbon dioxide during photosynthesis. However, the anthropogenic addition of carbon
dioxide and other greenhouse gases into the atmosphere has greatly exceeded the capac-
ity of the natural environment to remove them (USEPA 2009c). As a result, greenhouse
gas concentrations have been increasing (NOAA 2009). Figure 8.24 shows the process of
photosynthesis.
8.4.6.9  Carbon Monoxide
Carbon monoxide is created when fuel is not burned completely. Carbon monoxide is
formed naturally and anthropogenically. The most significant source of carbon monoxide
is from automobile exhaust (USEPA 2008a). Inside homes, significant sources of carbon
dioxide emissions are natural gas and oil furnaces, hot water heaters, appliances, wood
burning stoves and fireplaces. Carbon monoxide is also created as a by-product of sev-
eral industrial processes including metal melting and chemical synthesis (USDHH 2009).
From 1980 to 2008, there was a 79% decrease in carbon dioxide in the United States. This
decrease was attributed to improved air pollution control equipment for stationary and
mobile sources of air pollution (USEPA 2008a).
8.4.6.10  Ozone
Ozone is a gas occurring in Earth's upper atmosphere and at ground level. As noted in
Chapter 7, ozone in the upper atmosphere is greatly beneficial to life on Earth because it
filters ultraviolet radiation, but ozone occurring at ground level is considered an air pol-
lutant (USEPA 2009e). Ground-level ozone is not emitted directly into the air—it is created
by chemical reactions between oxides of nitrogen and VOCs in the presence of sun-
light. Emissions from automobile exhaust, gasoline vapors, chemical solvents, electrical
Sunlight
6H 2 O+ 6CO 2
C 6 H 12 O 6 + 6O 2
Water +Carbon dioxide
Glucose (a carbohydrate) +Oxygen
FIGURE 8.24
Photosynthesis and the removal of carbon dioxide.
 
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