Biomedical Engineering Reference
In-Depth Information
Perchlorate An anion consisting of one chlorine atom and four oxygen atoms, with the
chlorine atom present at an oxidation state of +7. Perchlorate occurs naturally; because it is a
potent oxidizer, it also has been manufactured and used for solid rocket propellants and
explosives.
Perchloroethene (PCE, perchloroethylene,
tetrachloroethene,
tetrachloroethylene)
A colorless, nonflammable organic solvent, CCl 2
¼
CCl 2 , used in dry-cleaning solutions and as
an industrial solvent.
The rate at which liquids pass through soil or other materials in a specified
Permeability
direction.
Permeable reactive barrier (PRB) A permeable zone containing or creating a reactive
treatment area oriented to intercepting and remediating a contaminant plume.
pH An expression of the intensity of the basic or acid condition of a liquid; may range from
0 to 14, where 0 is the most acid and 7 is neutral. Natural waters usually have a pH between 6.5
and 8.5.
Phytoaugmentation The addition of bacterial genes into plants to confer degradation
capacities.
Phytoremediation The use of plants and, in some cases, the associated rhizosphere (root
zone) microorganisms for in situ remediation of contaminants.
Planktonic The organisms passively floating or drifting in a water body. Planktonic
microbes in the subsurface are found in the aqueous phase, as opposed to those attached to
solids.
Plasmid A DNA molecule that is separate from, and can replicate independently of, the
chromosomal DNA. Plasmids are double-stranded and, in many cases, circular. Plasmids
usually occur naturally in bacteria, and can be used to introduce new genes into bacteria.
Plume A zone of dissolved contaminants. A plume usually originates from a contaminant
source zone and extends for some distance in the direction of groundwater flow.
Pneumatic fracturing Injection of gas into the subsurface at pressures exceeding the
natural in situ pressures and at flow volumes exceeding the natural permeability of the
subsurface. Creates a network of artificial fractures in a geologic formation that can
facilitate removal of contaminants out of the geologic formation; may be used to introduce
remedial agents.
Polychlorinated biphenyls (PCBs) A group of toxic, persistent chemicals used in electrical
transformers and capacitors for insulating purposes, and in gas pipeline systems as lubricant.
The sale and new use of these chemicals were banned by U.S. law in 1979.
Polymerase An enzyme used to catalyze the polymerization of new DNA or RNA against an
existing DNA or RNA template in the processes of replication and transcription.
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