Environmental Engineering Reference
In-Depth Information
Greenhouse gases:
gases in the atmosphere capable of absorbing and emitting radiation
within the thermal infrared range.
Ground moraine:
a moraine deposit formed under the ice between lateral moraines.
Ground moraine deposits may also be termed lodgment tills.
Groundwater:
water beneath the surface of the ground present in pore space, fractures, or
void spaces.
Groundwater recharge:
a hydrologic process where water migrates downward from the
surface and recharges groundwater.
Gypsum:
a sulfate mineral (CaSO
4
ยท 2H
2
O); an evaporite deposit.
Half-life:
the average amount of time required to degrade half or 50% of a specific con-
taminant population.
Half reaction:
the loss or gain of an electron.
Halite:
a mineral composed of sodium chloride (NaCl); an evaporite deposit.
Halogens:
a group of elements composed of fluorine (F), chlorine (Cl), Bromine (Br), and
Iodine (I).
Halogenated volatile organic compounds:
a group of organic compounds with a halogen
atom as part of its atomic structure.
Henry's law:
a measure of the tendency for substances to volatilize.
Hepatotoxin:
a chemical posing a risk of liver damage.
Herbicide:
a chemical compound used to kill unwanted plants.
Heterogeneity:
highly variable and poorly sorted geologic materials.
Hexavalent chromium:
the metallic element chromium in its positive-6 valence (hexava-
lent) state; all compounds containing Cr(VI) are potential occupational carcinogens.
High resolution aquifer profiling:
a technique of groundwater sampling and analysis
using multiple parameters capable of creating a detailed three-dimensional depic-
tion of the inner dynamics of groundwater contaminant plumes.
Homogeneity:
well-sorted geologic materials of low variability.
Humid microthermal climate:
continental climate characterized by strong seasonal varia-
tions and highly variable weather with ample precipitation throughout the year.
Hydraulic conductivity:
the ability of saturated geologic media to conduct water under an
induced hydraulic or pressure gradient.
Hydraulic gradient:
the rate of pressure or elevation change between two or more ground-
water monitoring points over the length of the flow path. Also referred to as
hydraulic head.
Hydraulic head:
the rate of pressure or elevation change between two or more groundwa-
ter monitoring points over the length of the flow path. Also referred to as hydrau-
lic gradient.
Hydrodynamic dispersion:
the tendency for contaminants to spread out from the path
normally expected from advective flow. Also referred to as dispersion.
Hydrograph:
a plot of stream discharge over a specified time interval.
Hydrologic cycle:
the solar-initiated and gravity-sustained renewable flow of water
between five major reservoirs: the oceans, atmosphere, ice caps, surface water, and
groundwater.
Hydrolysis:
cleavage of a molecule into two parts by the addition of a molecule of water.
Hygroscopic water:
water tightly held onto soil particles through adsorption and not
available for flow.
Igneous rocks:
rocks formed by the solidification of molten material either beneath Earth's
surface (termed plutonic igneous rocks) or at the surface (termed volcanic igneous
rocks).
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