Environmental Engineering Reference
In-Depth Information
Planetary albedo:
The fraction of incident solar radiation that is reflected by the
Earth-atmosphere system and returned to space, mostly by backscatter
from clouds in the atmosphere.
Plate tectonics:
A theory of global-scale dynamics involving the movement of
many rigid plates of the Earth's crust. Tectonic activity is evident along the
margins of the plates where buckling, grinding, faulting, and vulcanism
occur as the plates are propelled by the forces of deep-seated mantle con-
vection current. Geothermal resources are often associated with tectonic
activity, as it allows groundwater to come in contact with deep subsurface
heat sources.
Point absorber:
A floating structure that absorbs energy in all direction by virtue
of its movements at or near the water surface. It may be designed so as to
resonate (i.e., move with larger amplitudes than the waves themselves). This
feature is useful for maximizing the amount of power that is available for
capture. The power take-off system may take a number of forms, depending
on the configuration of displaces and reactors.
Point source:
A source of pollution that involves discharge of waste from an identifi-
able point, such as a drainage pipe, smokestack or water-treatment plant.
Poletimber trees:
Live trees that are at least 5.0 inches d.b.h. but smaller than saw-
timber trees.
Polycrystalline diamond compact (PDC) drilling bit:
A drilling bit that uses poly-
crystalline diamond compact inserts on the drill bit to drill by means of
rotational shear of the rock face.
Pondage:
The amount of water stored behind a hydroelectric dam of relatively small
storage capacity; the dam is usually used for daily or weekly control of the
flow of the river.
Population:
An interbreeding group of plants or animals; the entire group of organ-
isms of one species.
Porosity:
The ratio of the aggregate volume of pore spaces in rock or soil to its total
volume, usually stated as a percent.
Power factor:
The ratio of real power (kilowatt) to apparent power kilovolt-ampere
for any given load and time.
Powerhouse:
A structure at a hydroelectric plant site that contains the turbine and
generator.
Prescribed fire:
The application of fire to wildland fuels, either by natural or inten-
tional ignition, to achieve identified land use objectives.
Primary wood-using mill:
A mill that converts roundwood products into other
wood products. Common examples are sawmills that convert sawlogs into
lumber and pulp mills that convert pulpwood roundwood into wood pulp.
Process heating:
The direct process end use in which energy is used to raise the
temperature of substances involved in the manufacturing process.
Program tree:
A tree planted within a site area as a result of a shade tree program.
Propane (C
3
H
8
):
A straight-chain saturated (paraffinic) hydrocarbon extracted from
natural gas or refinery gas streams which is gaseous at standard tempera-
ture and pressure.
