Contaminated and Hazardous
Waste Site Management Glossary
G
Gaining Stream: A stream
or part of a stream where the flow is solely or partly contributed to by the inflow
of groundwater. Also called Effluent Stream.
Galvanic:
Describes geophysical techniques that require direct contact with the ground in
order to pass current. The alternative is to induce currents in the earth. Gas
Chromatography (GC): A method for separating, identifying and measuring concentrations
of organic compounds. Compounds pass through a chromatographic column and the
different rates of travel through it form the basis for their separation and identification.
Detection limits are usually 1 to 10 micrograms per litre. Gas
Chromatography/Mass Spectroscopy (GC/MS): A method for separating, identifying,
and quantifying organic compounds. The compounds are separated in the GC, but
their identification is based on both their retention time in the GC column and
their mass spectral pattern. Quantification is achieved by measuring peak heights
in the mass spectra. Detection limits are usually 5 to 10 micrograms per litre. Gas
Drive Pump: The pump mechanism depends on lifting a column of water from within
the pump body and attached tubing by using pressurized gas. Geomagnetic
Field: The Earth's magnetic field. Geomorphology:
Geomorphology is the science dealing with the origin and evolution of land forms.
Geophones: Receivers
used to record the seismic energy arriving from a source, in seismic geophysical
methods. Geophysical
Mapping: Locating geophysical anomalies in space (as opposed to time, which is
geophysical monitoring). Geophysical
Monitoring: Observing the change in a geophysical measurement with time. Glacio-Fluvial
Deposits: Deposits related to the joint action of glaciers and meltwater streams.
Gradient: The
rate of change in value of a physical or chemical parameter per unit change in
position. For example, hydraulic gradient is equal to the difference in head measured
at two points (usually wells) divided by the distance separating the two points.
The dimensions of head and distance are both lengths, therefore the gradient is
expressed as a dimensionless ratio (L/L). Grain
size: General dimensions of sediment or rock particles. The grain size distribution
describes the occurrence of sediment grains of different sizes and can be related
to the hydraulic conductivity of the granular material. Graphite
Furnace Atomic Absorption (GFAA): Atomic absorption which utilizes a graphite
cell for excitation. Ground
Penetrating Radar (GPR): A geophysical method in which bursts of electromagnetic
energy are transmitted downwards from the surface, to be reflected and refracted
by velocity contrasts within the subsurface. Also known as "Ground Probing
Radar". Groundwater:
Underground water that fills pores in soils or openings in rocks to the point
of saturation. In aquifers, groundwater occurs in sufficient quantities for use
as drinking and irrigation water and other purposes. Groundwater
Catchment Area: An area contributing natural replenshment (recharge) of the groundwater
regime. It may include localized discharge areas. Groundwater
Divide: The rather vague division between groundwater basins. When the divide
meets the land surface, water on one side of the divide will flow into one groundwater
system, while water recharging on the other side of the divide will flow into
another groundwater system or basin. Somewhat analogous to surface water basins
and divides. Groundwater
Flow: Movement of water through openings in sediment and rock of the saturated
zone. Groundwater
Mining: Permanent depletion of groundwater reserves. Groundwater
Quality Assessment: The process of analyzing the chemical characteristics of groundwater
to determine whether any hazardous materials exist. Groundwater
Table: That surface below which rock, gravel, sand or other material is saturated.
It is the surface of a body of unconfined groundwater at which the pressure is
atmospheric. Groundwater
Zone: All the rocks in the saturated zone, including those containing perched
groundwater. Grout:
A watery mixture of cement (and commonly bentonite) without aggregate that is
used to seal the annular space around well casings to prevent infiltration of
water or short-circuiting of vapor flow.
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