Environmental Engineering Reference
In-Depth Information
Contamination:
the introduction of harmful substances into an ecosystem; typically
anthropocentric-manufactured chemicals.
Contaminant fate and transport:
a description of what happens to a contaminant after it
has been released into the environment.
Contaminant risk factor:
a method to calculate the potential risk of a contaminant in air,
soil, or water by combining the elements of toxicity, mobility, and persistence.
Contaminant risk factor for groundwater:
the environmental risk posed by specific con-
taminants to contaminant groundwater.
Continental drift:
theory originally proposed by Alfred Wegener in 1912 that the conti-
nental land masses are not stationary and move.
Convection:
vertical advection of air, water, or other fluids as a result of thermal differences.
Covalent bond:
a form of chemical bonding characterized by sharing pairs of electrons
between atoms.
Cross-bedding:
sets of bedded sediments at different, on lapping, and inclined angles.
Cross-dating:
technique used to help understand sedimentary environments and the pro-
cesses leading to the origin of their sediments. Also referred to as facies analysis.
Cultural eutrophication:
when anthropogenic activities such as fertilization or sewage
discharges bring excess nutrients into water bodies.
Cultural landscape:
the product of human interaction with the natural landscape, with
culture acting as the agent, and the natural area as the medium.
Cyanide:
any chemical compound containing the cyano group consisting of a carbon atom
triple-bonded to a nitrogen atom.
Darcy's law:
describes the flow of a fluid through a porous medium.
Debris flow:
the rapid downslope plastic flow of a mass of regolith or debris. Commonly
creates an apron-like or tongue-like area at its terminus with a very irregular
surface.
Delta deposits:
sedimentary strata originating through the deposition at the mouth of a
river or stream discharging into a large body of water such as a lake or ocean.
Dense nonaqueous phase liquids:
organic compounds that do not readily mix or dissolve
in water and are heavier than water.
Desiccation cracks:
formed when a fine-grained deposit (most often clay size particles)
undergoes drying and is subsequently buried, preserving the feature. Also
referred to as mudcracks.
Diagenesis:
any chemical, physical, or biological change a sediment undergoes following
its initial deposition.
Diffusion:
the movement of a chemical from an area of higher concentration to an area
of lower concentration due to the random motion of the chemical molecules. Also
referred to as molecular diffusion.
Dioxins:
a diverse set of halogenated substances; includes other compounds called furans.
Dip:
the angle a geologic deposit, feature, or structure is tilted relative to the horizontal
plane.
Disconformity:
a type of unconformity existing between parallel layers of sedimentary
rocks.
Dispersion:
the tendency for contaminants to spread out from the path normally expected
from advective flow. Also referred to as hydrodynamic dispersion.
Dissolve:
to cause a substance to pass into solution.
Dolostone:
a sedimentary rock composed of magnesium-calcium carbonate (CaMg[CO
3
]
2
)
and associated with a marine-type environment.
Dredging:
a sediment remedial method where submerged material is excavated.
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