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Contaminated and Hazardous Waste Site Management

Glossary P

P-Wave: An elastic body wave in which particles move in the direction of propagation. It is the wave assumed in most seismic surveys. Also called primary or push-pull wave.

Packer: A device placed in a well or borehole to isolate or seal a section at a certain level.

Paraffins: See Alkanes.

Partial Pressure: The portion of total vapor pressure in a system due to one or more constituents in the vapor mixture.

Particle Mass Density: The oven-dried mass of the sample divided by the volume of the solid particles.

Partitioning: Chemical equilibrium condition where a chemical's concentration is apportioned between two different phases according to the partition coefficient, which is the ratio of a chemical's concentration in one phase to its concentration in the other phase.

Pathogen: A disease-producing agent; usually a living organism.

Peat: An unconsolidated deposit of partially decomposed plant matter with high moisture content, in a water-saturated environment.

Percentage Frequency Effect (PFE): The percent difference in resistivity measured at two frequencies (one high, one low). It is the basic polarization parameter measured in frequency domain resistivity surveys. Equivalent to chargeability in time domain surveys.

Percent Difference (%D): The percent difference indicates both the direction and the magnitude of the comparison (i.e., the percent difference may be either negative, positive, or zero). In contrast, see relative percent difference below.

Percent Moisture: An approximation of the amount of water in a soil/sediment sample made by drying an aliquot of the sample at 105C. The percent moisture determined in this manner also includes contributions from all compounds that may volatilize at or below 105C, including water. Percent moisture may be determined from decanted samples and from samples that are not decanted.

Percent Solids: The proportion of solid in a soil sample determined by drying an aliquot of the sample.

Perched: Normally refers to a perched water table, which is a water table for a zone saturated with water, but underlain by an unsaturated zone and another water table. Often caused by a low-permeability layer which caused infiltrating water to "pond" or perch above it.

Perched Aquifer: A special case of unconfined aquifer which occurs wherever an impervious (or semipervious) layer of limited areal extent is located between the regional water table of an unconfined aquifer and the ground surface.

Perched Groundwater: Groundwater separated from another underlying body of groundwater by a confining layer, often clay or rock.

Perched Water Table: A separate continuous body of groundwater lying (perched) above the main water table. Clay beds located within a sedimentary sequence, if of limited aerial extend, may have a shallow perched groundwater body overlying them.

Percolation: The downward flow or filtering of water or other liquids through subsurface rock or soil layers, usually continuing downward to groundwater.

Percussion Drilling: A method in which a hammering action by a bit breaks rock into small particles which can be removed from the borehole, thus advancing the borehole.

Performance Evaluation (PE) Sample: A sample of known composition provided by regulatory agency for laboratory analysis.

Peristaltic Pump: A low-volume pump in which suction is induced through the compression of a flexible tube by a rotor.

Permafrost: Perennially frozen ground in areas where the temperature remains at or below 0o C for two or more years in a row.

Permanent Magnetism: See Remanent Magnetism.

Permeability: A qualitative description of the relative ease with which rock, soil, or sediment will transmit a fluid (liquid or gas). Often used as a synonym for hydraulic conductivity or coefficient of permeability.

Permeable Reaction Wall: Is similar to a cutoff wall, but the wall is relative to aquifer permeable so that groundwater flows through it unimpeded. The wall has reactive materials within it to cause destruction or absorption (or both) of the contaminants. A permeable reaction wall can be a passive alternative to pump-and-treat for plume control.

Permeameter: A laboratory device which measures the intrinsic permeability and hydraulic conductivity of a solid or rock sample.

Permittivity: The property which enables a three-dimensional material to store electrical charge; i.e. its capacitivity.

Petrochemicals: Chemical substances produced from petroleum in refinery operations and as fuel oil residues. These include fluoranthene, chrysene, mineral spirits, and refined oils. Petrochemicals are the bases from which volatile organic compounds (VOCs), plastics and many pesticides are made. These chemical substances are often toxic to humans and the environment.

pH: A measure of the acidity of a solution. pH is equal to the negative logarithm of the concentration of hydrogen ions in a solution. A pH of 7 is neutral. Values less than 7 are acidic, and values greater than 7 are basic.

Phase: A homogeneous, physically-distinct portion of the subsurface. For example, groundwater, soil gas. For geophysical use, see In-phase and Phase Shift.

Phase Shift: A measure of the offset between two periodic signals of the same frequency. Measured in degrees or radians/milliradians.

Phototrophs: Organisms that use light to generate energy (by photosynthesis) for cell synthesis.

Phreatophytes: Plants with deep root systems which allow them to get water from the groundwater or the capillary fringe.

Physical Chemical Separation: The treatment process of adding a chemical to a substance to separate the compounds for further treatment or disposal.

Piezometer: A nonpumping well, generally of small diameter, which is used to measure the elevation of the water table or potentiometric surface. A piezometer generally has a short well screen and the water level within the casing is considered to be representative of the potentiometric surface at that particular depth in the aquifer.

Piezometer Nest: A set of two or more piezometers set in close proximity to one another but screened at different depths. This allows for determination of vertical flow gradients or differences in water chemistry with depth.

Piezometric Level: See Potentiometric Surface.

Piezometric Surface: An outdated term for "potentiometric surface".

Pilot Test: Operation of a small-scale version of a larger system to gain information relating to the anticipated performance of the larger system. Pilot test results are typically used to design and optimize the larger system.

Piston Pump: A pump that has a piston rod, cylinder and check valve mechanism which forces water to the surface through positive displacement.

Pitot Tube: A device used to measure the total pressure of a fluid stream that is essentially a tube attached to a manometer at one end and pointed upstream at the other.

Plasticity: The property of a solid body when it experiences a permanent change in shape or size due to a stress exceeding a certain value.

Plasticity Index (PI): The range of water content where the soil is in a plastic state. PI is calculated as the difference between the percent liquid limit and percent plastic limit.

Plastic Limit (PL): The lower limit of the plastic state of a soil (see Atterberg Limits).

Plastic Soil: One that will deform without shearing (typically silts or clays). Plasticity characteristics are measured using a set of parameters known as Atterberg Limits.

Plume: A body of contaminated groundwater or vapour originating from a specific source and influenced by certain factors such as local groundwater or soil vapour flow patterns and character of the aquifer. The zone of contamination that exhibits dissolved-phase contaminants at concentrations above some specified concentration level, such as a drinking water limit, detection limit or background. The volume of the subsurface that encompasses the plume also must encompass the residual lenses or pools of NAPL that feed dissolved-phase mass to the plume. To restore permanently groundwater at a site, both the plume and the immiscible-phase liquid (residual, lenses and pools) must be removed. To avoid confusion, the term "plume" should not be used to refer to a pool of free phase immiscible liquid. Plume removal refers to the removal of the dissolved-phase mass that constitutes the plume. NAPL removal refers to removal of the immiscible-phase liquid.

Poisson Ratio: The ratio of the transverse contracting strain to the elongation strain when a rod is stretched by forces applied at its ends, parallel to the its axis.

Polarize, Polarization, Polarizable: Separation of charge, as in induced polarization or IP.

Polishing: Refers to the application of remedial technologies to NAPL zones which have been reduction remediated previously (i.e., removal of immiscible-phased liquid) by other technologies. polishing is a cleanup phase that would normally be applied in order to remove or destroy dissolved-phase liquids in residual, lenses, or pools. To achieve 'groundwater restoration', an

aquifer would generally need to be polished after other remedial measures have been taken to remove nearly all of the mass of immiscible-phase (NAPL) liquid.

Pollution: Generally, the presence of matter or energy whose nature, location or quantity produces undesired health or environmental effects.

Polychlorinated Biphenyls (PCBs): A group of toxic chemicals used for a variety of purposes including electrical applications, carbonless copy paper, adhesives, hydraulic fluids, microscope immersion oils and caulking compounds. PCBs are also produced in certain combustion processes. PCBs are extremely persistent in the environment because they are very stable, non-reactive and highly heat resistant. Chronic exposure to PCBs is believed to cause liver damage. It also is known to bioaccumulate in fatty tissues. PCB use and sale was banned in 1979 with the passage of the Toxic Substances Control Act.

Polycyclic Aromatic Hydrocarbons or Polyaromatic Hydrocarbons (PAHs): PAHs, such as pyrene, are a group of highly reactive organic compounds found in motor oil. They are a common component of creosotes and can cause cancer.

Polynuclear Aromatic Hydrocarbons (PNAs): PNAs, such as naphthalene and biphenyls, are a group of highly reactive organic compounds that are a common component of creosotes, which can be carcinogenic.

Pool: A zone of free-phase immiscible liquid that resides at the bottom of an aquifer. A pool rests on top of an aquitard. A pool may be in an immobile state or it may be in a state of motion, depending on whether or not free-phase liquid is being added to the pool.

Pore Pressure: The stress produced by fluid which fills the voids between soil or rock particles.

Pore Space: An opening, void or interstice in a soil or rock mass.

Pore Volume: The volume of water (or air) that will completely fill all of the void space in a given volume of porous matrix. Pore volume is equivalent to the total porosity. The rate of decrease in the concentration of contaminants in a given volume of contaminated porous media is directly proportional to the number of pore volumes that can be exchanged (circulated) through the same given volume of porous media.

Porosity: The ratio of the volume of pore spaces in a rock or sediment to the total volume of the rock or sediment.

Porosity, Primary: The pore spaces which were created at the time of deposition of a soil or rock unit.

Porosity, Secondary: The pore spaces which were created after the time of deposition of a soil or rock unit (e.g. fractures, solution channels).

Potential Energy: Energy derived from position rather than motion, with respect to a specified datum in a field of force.

Potential Well Yield: An estimate of well yield generally above the existing yield rate or test rate, but considered possible on the basis of available information, data and present well performance.

Potentiometric Map: A map which shows through contour lines or other symbols, the potentiometric surface elevation of an aquifer.

Potentiometric Surface: A surface that represents the level to which water in a confined aquifer would rise in a well tapping the aquifer. If the head varies significantly with depth in the aquifer, then there may be more than one potentiometric surface, depending upon the depth at which the potentiometric surface is measured. The water table can be considered to be the potentiometric surface for an unconfined aquifer.

ppm: Parts per million (10,000 ppm = 1%).

Precipitation: a) Formation of solids out of dissolved constituents; it is caused by a change in conditions (e.g. temperature) b) Water that falls to the ground surface from the atmosphere as rain, snow, hail, sleet, etc..

Precision: The reproducibility of a measurement; the closeness of each of a set of similar measurements to the arithmetic mean of that set.

Preliminary Assessment: The process of collecting and reviewing available information about a known or suspected waste site or release to determine if a threat or potential threat exists.

Preparation Blank (reagent blank, method blank): An analytical control that contains distilled/deionized water and reagents, which is carried through the entire analytical procedure (digested and analyzed). An aqueous method blank is treated with the same reagents as a sample with a water matrix; a solid method blank is treated with the same reagents as a soil sample.

Preservative: A chemical added to organic (or inorganic) water samples to maintain the integrity of the sample. Some common preservatives include nitric acid, hydrochloric acid, phosphoric acid, sodium hydroxide, and refrigeration. Some samples are also contained in amber bottles to prevent deterioration of the sample by light.

Pressure Gradient: A pressure differential in a given medium (e.g., water or air) which tends to induce movement from areas of higher pressure to areas of lower pressure.

Pressure Head: The height of a column of static fluid which is necessary to develop a specific pressure.

Primary (magnetic field): The magnetic field generated by an EM transmitter. May induce a secondary magnetic field.

Primary Porosity: See Porosity, Primary.

Procaryotes: A cellular organism in which the nucleus has no limiting membrane.

Processing: Geophysically, to change data so as to emphasize certain aspects or correct for known influences, thereby facilitating interpretation.

Profiling: In geophysics, a survey method whereby an array of sensors is moved along the Earth's surface without change in its configuration, in order to detect lateral changes in the properties of the subsurface (faults, buried channels, etc..). The alternative is usually a sounding.

Protocol: Describes the exact procedures to be followed with respect to sample receipt and handling, analytical methods, data reporting and deliverables, and document control. Used synonymously with Statement of Work (SOW).

Protozoa: Single-celled, eucaryotic microorganisms without cell walls. Most protozoa are free-living although many are parasitic. The majority of protozoa are aerobic or faculatively anaerobic heterotrophs.

Pseudosection: A cross section showing the distribution of a geophysical property, such as seismic travel time, from which the distribution of the geological property of interest (depth to bedrock, for example) can be interpreted.

Psi (pounds per square inch): A unit of pressure or pressure drop across a flow resistance. One psi is equivalent to the pressure exerted by 2.31 feet of water column (0.0684 atmospheres).

Psig (pounds per square inch (gauge): 0 psig = 14.696 psia (psi (absolute)) = 1.0 atmosphere.

Pugmill: A chamber in which water and soil are mixed together. Typically mixing is aided by an internal mechanical stirring/kneading device.

Pumping Interference: The condition occurring when a pumping well lowers the water level in a neighbouring well.

Pumping Test: An aquifer test in which a well is pumped for a certain period of time and the change in hydraulic head in observation wells is recorded. It is used to determine the capacity of a well and hydraulic characteristics of the aquifer.

Pump-and-Treat: This term is reserved for the removal of water containing dissolved-phase contaminants by means of wells or trenches. The water is treated on surface. Pump-and-treat can be used either for plume migration control or hydraulic containment in the zone where immiscible-phase liquid occurs or both.

Purge, Purging: Process of removing stagnant water from a well before sampling.

Purge-and-Trap (P&T): Analytical technique (device) used to isolate volatile (purgeable) organics by stripping the compounds from water or soil by a stream of inert gas, trapping the compounds on an adsorbent such as a porous polymer trap, and thermally desorbing the trapped compounds into the gas chromatographic column.

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