478 Glossarysecondary treatment Biological treatment of wastewater to
decompose suspended organic material; secondary treatment
reduces the water’s biochemical oxygen demand.
second law of thermodynamics A physical law which states that
when energy is converted from one form to another, some of it
is degraded into heat, a less usable form that disperses into the
environment.
sewage Wastewater from drains or sewers (from toilets, washing
machines, and showers); includes human wastes, soaps, and
detergents.
shelterbelt A row of trees planted as a windbreak to reduce soil
erosion of agricultural land.
sick building syndrome Eye irritations, nausea, headaches,
respiratory infections, depression, and fatigue caused by indoor
air pollution.
smelting The process in which ore is melted at high temperatures to
separate impurities from the molten metal.
soil erosion The wearing away or removal of soil from the land.
soil horizons Horizontal layers into which many soils are organized,
from the surface to the underlying parent material.
soil The uppermost layer of Earth’s crust, which supports terrestrial
plants, animals, and microorganisms.
solar thermal electric generation A means of producing electricity in
which the sun’s energy is concentrated using mirrors or lenses
onto a fluid-filled pipe; the heated fluid is used to generate
electricity.
source reduction An aspect of waste management in which
products are designed and manufactured in ways that decrease
the amount of solid and hazardous waste in the solid waste
stream.
species richness The number of different species in a community.
spent fuel Used fuel elements that were irradiated in a nuclear
reactor.
spoil bank A hill of loose rock created when the overburden from a
new trench is put into the already excavated trench during strip
mining.
standing-water ecosystem A body of fresh water surrounded by land
and whose water does not flow; a lake or a pond.
subsistence agriculture Traditional agricultural methods that are
dependent on labor and a large amount of land to produce
enough food to feed oneself and one’s family.
subsurface mining The extraction of mineral and energy resources
from deep underground deposits.
surface mining The extraction of mineral and energy resources near
Earth’s surface by first removing the soil, subsoil, and overlying
rock strata.
surface water Precipitation that remains on the surface of the land
and does not seep down through the soil.
sustainability The ability to meet humanity’s current needs without
compromising the ability of future generations to meet their
needs.
sustainable agriculture Agricultural methods that maintain soil
productivity and a healthy ecological balance while having
minimal long-term impacts.
sustainable c onsumption The use of goods and services that satisfy
basic human needs and improve the quality of life but that also
minimize resource use.certain metals in such a way that the film generates electricity
when solar energy is absorbed.
plate tectonics The study of the processes by which the lithospheric
plates move over the asthenosphere.
point source pollution Water pollution that can be traced to a specific
point of entry.
population A group of organisms of the same species that live
together in the same area at the same time.
population ecology The branch of biology that deals with the number
of individuals of a particular species found in an area and how
and why those numbers increase or decrease over time.
poverty A condition in which people are unable to meet their basic
needs for food, clothing, shelter, education, or health.
precautionary principle The idea that new technologies, practices,
or materials should not be adopted until there is strong evidence
that they will not adversely affect human or environmental
health.
predation The consumption of one species (the prey) by another (the
predator).
primary air pollutants Harmful chemicals that enter directly into
the atmosphere due to either human activities or natural
processes.
primary treatment Treatment of wastewater that involves removing
suspended and floating particles through mechanical processes.
radiative forcing For greenhouse gases, the capacity to retain heat in
Earth’s atmosphere.
rangeland Grassland area that is not intensively managed and is
used for grazing livestock.
renewable resources Resources that are replaced by natural
processes and that can be used forever, provided they are not
overexploited in the short term.
replacement-level fertility The number of children a couple must
produce to “replace” themselves.
restoration ecology The study of the historical condition of a human-
damaged ecosystem, with the goal of returning it as closely as
possible to its former state.
risk assessment The quantitative and qualitative characterization of
risks so that they can be compared, contrasted, and managed.
risk The probability of harm (such as injury, disease, death, or
environmental damage) occurring under certain circumstances.
runoff The movement of fresh water from precipitation and
snowmelt to rivers, lakes, wetlands, and the ocean.
salinization The gradual accumulation of salt in soil, often as a result
of improper irrigation methods.
saltwater intrusion The movement of seawater into a freshwater
aquifer near the coast.
sanitary landfill The most common disposal site for solid waste,
where waste is compacted and buried under a shallow layer of
soil.
savanna A tropical grassland with widely scattered trees or clumps
of trees.
scientific method The way a scientist approaches a problem, by
formulating a hypothesis and then testing it.
secondary air pollutants Harmful chemicals that form in the
atmosphere when primary air pollutants react chemically with
one another or with natural components of the atmosphere.Berg_Gloss_475-479v2.indd 478 5/15/13 12:36 PM