Environmental Engineering Reference
In-Depth Information
Feedback The process by which a component part of a system is controlled in part by the products of its own
activities. Feedbacks may be either negative (counteracting the initial activity of the component) or positive
(reinforcing the initial activity of the component).
Fermentation A microbially mediated, energy-yielding redox reaction in which an organic molecule is split such
that one part of the molecule is oxidized and another part is reduced.
Heterogeneity Differentiation in structure or process over space or time in any system.
Heterotrophic Used to describe both organisms and ecosystems. Heterotrophic organisms are those that obtain
their carbon (and energy) from ingestion of organic matter. Net heterotrophic ecosystems are those where total
respiration exceeds gross primary production. The opposite of heterotrophic is autotrophic.
Homeotherm An animal that maintains a nearly constant body temperature, usually above that of the environ-
ment. Sometimes also called an endotherm or warm-blooded animal. The opposite of a homeotherm is a
poikilotherm.
Humus Partly decomposed organic matter in the soil.
Hypereutrophic Having extremely high primary production, usually associated with high nutrient inputs.
Hypolimnion The lower part of a stratified lake. The epilimnion and metalimnion (or thermocline) lie above the
hypolimnion.
Hysteresis The dependence of a variable on the history as well as the present state of independent variables.
Immobilization Uptake of dissolved nutrients that are incorporated into organic matter by organisms; usually
refers to uptake of dissolved nitrogen or phosphorus by bacteria or fungi.
Isotope Any of multiple forms of an element that have different numbers of neutrons, but the same number of
protons and electrons, and similar chemical properties. Isotopes may be either stable or radioactive (see Box
1.3 in Chapter 1).
Leaching The removal of soluble substances from rocks or soils by percolating waters.
Lignin A highly complex, uncharacterized macromolecule present in plants (especially woody species) made up
of diverse subunits containing phenolic rings (see Figure 4.7 in Chapter 4) and resistant to decomposition.
Lithosphere The crust and upper mantle of Earth.
Lysimeter A device for sampling soil water.
Macronutrients Elements needed in large amounts by living organisms (carbon, nitrogen, hydrogen, oxygen,
phosphorus, sulfur, potassium, magnesium, sodium, and calcium, plus silicon for diatoms and some land
plants). Elements needed only in small amounts are called micronutrients.
Mass balance The application of the law of the conservation of matter to ecosystems. If a substance is subject to
mass balance, the sum of all inputs, outputs, and changes in storage must equal zero.
Mesotrophic Having moderate primary productivity (less than a eutrophic system, but more than an oligotro-
phic system).
Micronutrients Elements needed in small amounts by living organisms (iron, manganese, zinc, copper, boron,
molybdenum, chlorine, vanadium, and cobalt). Elements needed in large amounts are called macronutrients.
Mineralization The breakdown of organic matter into its inorganic constituents.
Net ecosystem production The difference between gross primary production and the summed respiration of
autotrophs and heterotrophs. Net ecosystem production can be either positive or negative.
NO
x
,NO
y
NO
x
includes nitrogen oxides (NO and NO
2
); NO
y
is NO
x
plus its oxidation products such as nitric
acid (HNO
3
). NO
x
and NO
y
are important in the atmospheric cycling of nitrogen.
Oligotrophic Having low primary production (and usually low nutrient concentrations as well).
Oxidation A chemical reaction in which a substance gains electrons. The opposite reaction is reduction.
Oxidation state A measure of the degree of oxidation of an atom, ion, or molecule. Many elements of ecological
interest can exist in multiple oxidation states.
Paleoecology The ecology of ecosystems from the past, often studied by tools such as the analysis of deposited
lake sediments.
Photic zone The surface zone of an aquatic ecosystem in which sufficient light exists to support photosynthesis.
Photooxidation The oxidation of organic matter by light.
Photosynthesis The use of light energy to fix carbon dioxide and water into organic matter.
Poikilotherm An animal whose body temperature varies along with environmental temperatures, as contrasted
with homeotherms. Also called ectotherms or cold-blooded animals.
