Contaminant Fate and Transport - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 308

PCBs, and many pesticides and herbicides may sorb to a soil particle and travel a signifi-
cant distance through wind action (USEPA 1998a). The size of particulate matter is signifi-
cant because the largest sizes tend to settle to the ground surface first. Smaller particles
can travel around the globe and remain suspended for years if favorable conditions exist
(USEPA 2008a). Here is some good news: there was a 10%-20% decline in atmospheric par-
ticulate matter within the urban areas of the United States between 2001 and 2007 (USEPA
2008a).
8.4.6.13 Bacteria, Parasites, and Viruses
Bacteria, parasites, and viruses are present in large numbers everywhere in the environ-
ment. They are in and on the food we eat, in and on our bodies, in the air we breathe and the
water we drink, in soil, and at depths within Earth. Many are beneficial, but some have the
potential to adversely affect our health and well-being (Madigan et al. 2008). Ominously,
these pathogens have evolved mechanisms to persist in the environment. Bacteria such as
Escherichia coli can persist in secondary, nonhost habitats for prolonged periods (Ksoll et al.
2007). Giardia and Cryptosporidium form cysts and oocysts, respectively, and these struc-
tures sustain these parasites outside their hosts until they are ingested through drinking
water (Wallis et al. 1996). Viruses, such as influenza, are more likely to persist in the envi-
ronment at colder temperatures. The dry, cold conditions pull moisture out of droplets
released by coughs and sneezes, which allows the virus to linger in the air. At winter
temperatures, the virus's outer covering, or envelope, hardens to a rubbery gel that could
shield the virus as it passes from person to person, the researchers have found. At warmer
temperatures, however, the protective gel melts to a liquid phase (Shaman and Kohn 2009).
8.4.6.14 Emerging Contaminants
Emerging contaminants including many pharmaceuticals, 1,4-dioxane, and perchlorates
are resistant to degradation and can remain in the environment for long periods of time
(ATSDR 2007d, 2008d). Many pharmaceuticals and drugs, 1,4-dioxane, and perchlorates
have been detected in groundwater where they can migrate long distances due to their
relatively high solubility and resistance to degradation.
Emerging contaminants are difficult to study because many have entered the environ-
ment from nontraditional sources such as residential septic systems, as opposed to indus-
trial sources (ATSDR 2008d; Barnes et al. 2008).
8.5 Summary and Conclusion
There are thousands of contaminants existing everywhere. After they are released, many
of them migrate in air, soil, and water. Some are persistent, while others resist degradation.
The geology and hydrogeology of urban areas play a significant role in affecting the fate
and transport of contaminants and determine their final disposition.
Automobile exhaust is responsible for a significant amount of the pollution released
every year in the United States and throughout the world. Contaminants associated with
automobile use affects the air we breathe, the water we drink, and may also affect our
global climate.