Environmental Engineering Reference
In-Depth Information
Glossary
Abiotic degradation:
degradation of a substance by processes not involving microorgan-
isms or fungi.
Acid:
any substance that when dissolved in water increases the concentration of the hydro-
gen ion H
+
and lowers the pH of the solution.
Acid rain:
precipitation with a pH of less than 7, resulting in large part from the reaction
between sulfur dioxide and water vapor in the atmosphere that produces sulfuric
acid.
Acute response:
characterized as a single high dose with rapid onset and disappearance
of symptoms.
Absorption:
a process by which a particle of gas or liquid enters a substance.
Adsorption:
the adhesion of molecules of gas, liquid, or dissolved solids to a surface.
Advection:
bulk transport of a liquid.
Adverse health effect:
a change in body function or cell structure potentially leading to
disease or health problems.
Aeolian deposits:
sediments deposited by wind action. Also known as eolian deposits.
Air sparging:
a groundwater remedial method that involves using injected air to volatil-
ize contaminants in groundwater. As the injected air rises through the saturated
zone and reaches the unsaturated zone, the vapors containing the contaminants
are removed from the ground using a soil-vapor extraction system.
Alluvial fan:
sedimentary deposit formed when a fast-flowing stream in steep terrain
suddenly slows where the slope decreases; this declining velocity results in the
deposition of sediments due to energy loss.
Amines:
a group of organic compounds that contain nitrogen and are basic.
Angle of repose:
the steepest angle a cohensionless slope can maintain without losing its
stability.
Angular unconformity:
an unconformity where horizontal strata or layers of sedimen-
tary rock are deposited on tilted and eroded strata.
Anisotropic:
high variability of a specific geologic feature when measured in different
directions.
Anthropogenic:
effects, processes, or materials derived from human activities.
Anthrosphere:
human-built or developed world.
Annular seal:
material of low hydraulic conductivity placed above a well screen to min-
imize the potential for the vertical migration of substances into the well. Also
referred to as bentonite seal.
Aquifer:
a mappable geologic unit composed of water-saturated porous media capable of
storing and transmitting significant quantities of water under ordinary conditions.
Aquifer system:
more than one generally interconnected aquifer at a given location.
Aroclor:
mixture of PCB compounds distinguished by a four-digit numbering system that
denotes characteristics of composition.
Artesian well:
a well drilled through impermeable strata into strata receiving water from
a higher elevation; this overburden of water creates pressure to force the water in
the aquifer to flow upward.
Artificial groundwater recharge:
artificially increasing the amount of water entering an
aquifer.
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