Botkin Environmental Science Earth as Living Planet 8th txtbk

G-14 Glossary
pollutant when present in the lower atmosphere above the
National Air Quality Standards.
Ozone shield Stratospheric ozone layer that absorbs ultraviolet
radiation.
Pandemic A worldwide disease outbreak.
Particulate matter Small particles of solid or liquid substances
that are released into the atmosphere by many activities,
including farming, volcanic eruption, and burning fossil
fuels. Particulates affect human health, ecosystems, and the
biosphere.
Passive solar energy system Direct use of solar energy
through architectural design to enhance or take advantage
of natural changes in solar energy that occur throughout
the year without requiring mechanical power.
Pasture Land plowed and planted to provide forage for
domestic herbivorous animals.
Peak oil Refers to the time in the future when one-half of
Earth’s oil has been exploited. Peak oil is expected to occur
sometime between 2020 and 2050.
Pebble A rock fragment between 4 and 64 mm in diameter.
Pedology The study of soils.
Pelagic ecosystem An ecosystem that occurs in the floating
part of an ocean or sea, without any physical connections
to the bottom of the ocean or sea.
Pelagic whaling Practice of whalers taking to the open seas
and searching for whales from ships that remained at sea
for long periods.
Per-capita availability The amount of a resource available
per person.
Per-capita demand The economic demand per person.
Per-capita food production The amount of food produced
per person.
Permafrost Permanently frozen ground.
Persistent organic pollutants Synthetic carbon-based compounds,
often containing chlorine, that do not easily break
down in the environment. Many were introduced decades
before their harmful effects were fully understood and are
now banned or restricted.
Pesticides, broad-spectrum Pesticides that kill a wide variety
of organisms. E.g. arsenic, one of the first elements used as
a pesticide, is toxic to many life-forms, including people.
Phosphorus cycle A major biogeochemical cycle involving the
movement of phosphorus throughout the biosphere and
lithosphere. This cycle is important because phosphorus is
an essential element for life and often is a limiting nutrient
for plant growth.
Photochemical oxidants Result from atmospheric interactions
of nitrogen dioxide and sunlight. Most common is
ozone (O 3 ).
Photochemical smog Sometimes called L.A.-type smog or
brown air. Directly related to automobile use and solar
radiation. Reactions that occur in the development of the
smog are complex and involve both nitrogen oxides and
hydrocarbons in the presence of sunlight.
Photosynthesis Synthesis of sugars from carbon dioxide and
water by living organisms using light as energy. Oxygen is
given off as a by-product.
Photovoltaics Technology that converts sunlight directly
into electricity using a solid semiconductor material.
Physiographic province A region characterized by a particular
assemblage of landforms, climate, and geomorphic history.
Pioneer species Species found in early stages of succession.
Placer deposit A type of ore deposit found in material
transported and deposited by agents such as running water,
ice, or wind. Examples include gold and diamonds found
in stream deposits.
Plantations In forestry, managed forests, in which a single
species is planted in straight rows and harvested at regular
intervals.
Plate tectonics A model of global tectonics that suggests
that the outer layer of Earth, known as the lithosphere, is
composed of several large plates that move relative to one
another. Continents and ocean basins are passive riders on
these plates.
Point sources Sources of pollution such as smokestacks,
pipes, or accidental spills that are readily identified and
stationary. They are often thought to be easier to recognize
and control than are area sources. This is true only
in a general sense, as some very large point sources emit
tremendous amounts of pollutants into the environment.
Polar amplification Processes in which global warming
causes greater temperature increases at polar regions.
Polar stratospheric clouds Clouds that form in the stratosphere
during the polar winter.
Polar vortex Arctic air masses that in the winter become isolated
from the rest of the atmosphere and circulate about
the pole. The vortex rotates counterclockwise because of
the rotation of Earth in the Southern Hemisphere.
Policy instruments The means to implement a society’s policies.
Such instruments include moral suasion (jawboning—
persuading people by talk, publicity, and social pressure);
direct controls, including regulations; and market processes
affecting the price of goods, subsidies, licenses, and deposits.
Pollutant In general terms, any factor that has a harmful
effect on living things or their environment.
Pollution The process by which something becomes impure,
defiled, dirty, or otherwise unclean.
Pollution prevention Identifying ways to avoid the generation
of waste rather than finding ways to dispose of it.
Pool (in a stream) A stream bed produced by scour.
Population A group of individuals of the same species
living in the same area or interbreeding and sharing genetic
information.
Population age structure The number of individuals or the
proportion of the population in each age class.
Population dynamics The causes of changes in population
size.
Population momentum or lag effect The continued growth
of a population after replacement-level fertility is reached.
Population regulation See Density-dependent population
effects and Density-independent population effects.
Population risk A term used in discussions of endangered
species to mean random variation in population—birth
rates and death rates—possibly causing species in low
abundance to become extinct.