Environmental Engineering Reference
In-Depth Information
parent material
The main component of soil, created from eroded and weathered existing geologic material in
a given area.
particulate matter
Solid or liquid particles suspended in the atmosphere or in water.
percolation
The movement of water through porous soil and rock.
perihelion
The orbital point in January when the Earth is closest to the sun.
permit trading
The practice in which governments issue certain levels of permits to polluters, who can then
trade or sell their permits to other polluters as needed. This promotes more sustainable environmental actions
through economic policy.
peroxyacetyl nitrate (PAN)
Produced by the reaction of some volatile organic hydrocarbons with oxygen and
nitrogen dioxide, partially responsible for some negative effects of smog.
persistence
The ability of a substance to remain in the environment for an extended period of time.
pH
Measures hydrogen ion concentrations on a scale of 1 to 14, with 7 being neutral; acidic substances range
from 1 to 6.9, and alkaline (or basic) substances range from 7.1 to 14.
photochemical smog
Smog formed when nitrogen dioxide (NO
2
) reacts with the heat of UV radiation from
the sun.
photosynthesis
The natural process in which plant chlorophyll converts carbon dioxide (CO
2
) and water
(H
2
O) into glucose (C
6
H
12
O
6
) and oxygen (O
2
) in the presence of sunlight.
physical weathering
Occurs when rock material is broken down without any chemical change taking place,
usually through gravitation, wind, running water, or ice expansion; also called mechanical weathering.
pioneer species
The first species to colonize an area that has not previously been colonized. A pioneer species
begins the first steps of ecological succession.
placer mining
A mineral mining technique that uses water to separate out the heavier minerals from lighter
mud and debris.
point-source pollution
Pollution emitted from a specific place, such as wastewater from an industrial plant,
acid drainage from a mine, noise from a jet plane, or oil from a tank.
polar air circulation cell
The air circulation cell that causes the polar convection current, extending north and
south from the temperate convection current.
polybrominated diphenyl ethers (PBDEs)
Chemicals that are used as flame retardants in household items
such as televisions, furniture, fabrics, wire insulation, drapes, small appliances, and other electronics.
population
A group of individuals of the same species living in the same area at the same time.
population density
The number of individuals in a population per unit area.
population dispersion
See
population distribution
.
population distribution
The spatial arrangement of organisms in an area, with types including random, uni-
form, or clumped distribution. Also called population dispersion.
