Science of Water : Concepts and Applications

Glossary 403
Benthic organism A form of aquatic life that lives on or near the bottom of stream, lakes, or
oceans.
Bioaccumulation The biological sequestering of a substance at a higher concentrations than
that at which it occurs in the surrounding environment or medium. Also, the process
whereby a substance enters organisms through the gills, epithelial tissues, dietary, or
other sources.
Bioavailability The capacity of a chemical constituent to be taken up by living organisms either
through physical contact or by ingestion.
Biochemical Chemical processes that occur inside or are mediated by living organisms.
Biochemical process A process characterized by, produced by, or involving chemical reactions
in living organisms.
Biochemical oxygen demand (BOD) The amount of oxygen required by bacteria to stabilize
decomposable organic matter under aerobic conditions.
Biodegradation Transformation of a substance into new compounds through biochemical reactions
or the actions of microorganisms such as bacteria.
Biological treatment A process that uses living organisms to bring about chemical changes.
Biomass The amount of living matter, in the form of organisms, present in a particular habitat,
usually expressed as weight per unit area.
Biota All living organisms of an area.
Bog A nutrient-poor, acidic wetland dominated by a waterlogged, spongy mat of sphagnum
moss that ultimately forms a thick layer of acidic peat; generally has no infl ow or outfl ow;
fed primarily by rain water.
Brackish water Water with a salinity intermediate between seawater and freshwater (containing
from 1000 to 10,000 mg/L of dissolved solids).
Breakdown product A compound derived by chemical, biological, or physical action upon a
pesticide. The breakdown is a natural process that may result in a more toxic or a less
toxic compound and a more persistent or less persistent compound.
Breakpoint chlorination The addition of chlorine to water until the chlorine demand has been
satisfi ed and free chlorine residual is available for disinfection.
C
Calcareous A rock or substance formed of calcium carbonate or magnesium carbonate by biological
deposition or inorganic precipitation, or containing those minerals in suffi cient
quantities to effervesce when treated with cold hydrochloric acid.
Capillary fringe The zone above the water table in which water is held by surface tension.
Water in the capillary fringe is under a pressure less than atmospheric.
Carbonate rocks Rocks (such as limestone or dolostone) that are composed primarily of minerals
(such as calcite and dolomite) containing a carbonate ion.
Center pivot irrigation An automated sprinkler system involving a rotating pipe or boom
that supplies water to a circular area of an agricultural fi eld through sprinkler heads or
nozzles.
Channel scour Erosion by fl owing water and sediment on a stream channel; results in removal
of mud, silt, and sand on the outside curve of a stream bend and the bed material of a
stream channel.
Channelization The straightening and deepening of a stream channel to permit the water to
move faster or to drain a wet area for farming.
Chemical treatment A process that results in the formation of a new substance or substances.
The most common chemical water treatment processes include coagulation, disinfection,
water softening, and fi ltration.