Environmental Engineering Reference
In-Depth Information
human exposures and ecosystem damages is much higher and may persist for decades
under certain conditions.
The following sections discuss how and where contaminant releases occur; how their
migration through the soil, groundwater, and atmosphere proceeds; and how they end up
in sinks. The chapter concludes with a brief description of the fate and transport for each
contaminant group.
8.2 Contaminant Releases into the Environment
The fate and transport of contaminants begins with their release into the environment.
Contaminant releases originate from numerous sources and under different circum-
stances; they vary on degree, concentration, duration, mass, volume, and whether a single
contaminant is released or if a mixture of contaminants are released. Each of these factors
influences their fate and transport. For instance, some releases may be very small and
avoid detection. On the other hand, some releases are so large and sudden (e.g., a tanker
spill) that they become the leading story of the next newscast. Sudden and large releases
increase the probability of severe environmental impairment or destruction, especially if
they occur in or near a sensitive ecological area.
Historically, there was no regulation of the disposal of wastes containing contaminants.
Until the mid-twentieth century, the most convenient and least costly method of waste dis-
posal was “up the stack or down the river” (Haynes 1954). We now know that the percep-
tion of a contaminant leaving your immediate vicinity and being gone forever is not true.
Today, many releases of contaminants are permitted but carefully monitored, such as
wastewater discharges from industrial and municipal sources and those to the atmo-
sphere from industrial and commercial sources and power plants. The legislation govern-
ing such releases (the Clean Water Act of 1972 and the Clean Air Act of 1990) permits a
point source (such as a wastewater plant or a smokestack) to release specific compounds at
low concentrations to ensure there are no adverse health and environmental effects detect-
able on the media they are released into (water or air). A majority of the other contaminant
releases into the environment are unintentional or accidental and occur from numerous
sources under a multitude of circumstances, and these include (Fetter 1993; Rogers 1996;
USGS 2006a)
• Permitted releases of contaminants in wastewater and air emissions
• Spills and leaks from several types of containers or operations, including
• Drums of various sizes and shapes
• Pipelines
• Above ground storage tanks
• Underground storage tanks
• Tanker trucks and other transport vehicles
• Tanker ships
• Railroad tanker cars
• Aircraft
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