February 2017 Compiled Glossary ITRC standard glossary, compiled from all ITRC web-based documents and current definitions. Terms may be used in all future team documents, to be customized for your specificity. A Abatement The act or process of lessening, reducing, or removing material or contaminants. Abiotic degradation Process in which a substance is converted to simpler products by physical or chemical mechanisms; examples include hydrolysis and photolysis. Absorption Absorption is the assimilation or incorporation of a gas, liquid, or dissolved substance into another substance. Accuracy Accuracy of an analytical measurement is how closely the result corresponds to the true value. This normally requires the use of standards in carefully calibrating the analytical methods. Acid mine drainage (AMD) A low pH, metal-laden, sulfate-rich drainage originating from a mined area that occurs where sulfur or metal sulfides are exposed to atmospheric conditions. It forms under natural conditions from the oxidation of sulfide minerals and where the acidity exceeds the alkalinity. See also acid rock drainage. Action level The generic term applied to any numerical concentration value which will be compared with environmental data to arrive at a decision or determination about a potential contaminant(s) of concern (from survey through remediation) or for a user-defined volume of media using environmental sample data. Active site Part of an enzyme where catalysis of the substrate occurs. Activity Refers to when a microorganism performs a specific function (e.g., sulfate reduction, metabolism of benzene) 1 February 2017 Activity patterns The activity or activities in which the receptor is assumed to be engaged involving details regarding where they are, when they were there, how long they were there, and over what area. Acute toxicity Any poisonous effect produced within a short period of time following an exposure, usually 24 to 96 hours (USEPA 2013). Adsorption Adsorption is the adhesion of molecules of gas, liquid, or dissolved solids to a surface. The term also refers to a method of treating wastes in which activated carbon is used to remove organic compounds from wastewater. Additionally, Adsorption is defined as the process by which nutrients such as inorganic phosphorous adhere to particles via a loose chemical bond with the surface of clay particles. Non-covalent bonding of a chemical to a solid surface. Advanced geospatial methods Methods that include an explicit spatial correlation model. These methods may also include spatial trend and statistical error components. Advanced methods are also known as geostatistical methods. Advanced sensors Munitions-classifying sensors that are designed with many transmit and receive coils rigidly assembled in a fixed-array configuration. The combination of multiple receive coils, large bandwidth electronics, and supporting sensor data results in the collection of significantly more data than can be collected with single-axis EM61 sensors. Advection Bulk transport of the mass of discrete chemical or biological constituents by fluid flow within a receiving water. Advection describes the mass transport due to the velocity, or flow, of the water body. It is also defined as: The process of transfer of fluids (vapors or liquid) through a geologic formation in response to a pressure gradient that may be caused by changes in barometric pressure, water table levels, wind fluctuations, or infiltration. Transport of a solute by the bulk motion of flowing groundwater. Advective groundwater flux The rate or movement of chemical or biological materials within a groundwater system per unit time in response to a concentration gradient or some advective force. Adverse human health effects Typically defined as an incremental lifetime cancer risk (for example, exceeding a range of 1E-4 to 1E-6) or a hazard quotient or hazard index (for example, one). 2 February 2017 Aerobic Pertaining to or caused by the presence of oxygen. Aerobic polishing cell (APC) A shallow pond which allows for aeration and settling of particles, typically following a BCR. Aliphatic A hydrocarbon compound in which the carbon atoms are in a straight-chain, branched, or cyclic arrangement and are saturated or unsaturated. Acyclic or cyclic, saturated or unsaturated, carbon compounds (excluding aromatic compounds). Alkane A group of chemicals (also known as paraffins or aliphatic hydrocarbons) for which the carbon atoms are all linked by single covalent bonds. Alkene A group of chemicals (also known as paraffins or aliphatic hydrocarbons) for which the carbon atoms contain at least one double bond. Amorphous Having no crystalline form. Anaerobic Pertaining to or caused by the absence of oxygen. Anisotropy The property of being directionally dependent (as opposed to isotropy, which means homogeneity in all directions). The degree of spatial correlation is dependent on direction, typically assessed using directional variograms, covariograms, or correlograms. Antagonism A chemical interaction that influences the toxicity of a chemical when one chemical interferes or inhibits the effect of the other chemical; for example, 4 + 6 = 8 (USEPA 2015h). Anthropogenic activity Activity resulting from human activities. Apatite Name given to a group of phosphate minerals, usually referring to hydroxylapatite distributed widely in igneous, metamorphic, and sedimentary rocks, often in the form of cryptocrystalline 3 February 2017 fragments. Hydroxylapatite is used in chromatographic techniques to purify proteins and other chemicals. Aqueous solubility Aqueous solubility represents the maximum concentration of the dense nonaqueous phase liquid (DNAPL) chemical constituents that can be dissolved in an aqueous solution (groundwater, for the purpose of this document). Archaea Microorganisms that are genetically distinct from bacteria. Methanogens are an example of archaea (www.biology-online.org, accessed online, 2013). Areal loading rate The amount of something applied to an area per time. Aromatic An organic compound that contains one or more benzene or equivalent heterocyclic rings. Aseptic Free from pathogenic microorganisms. Attenuation factor A ratio of the indoor air concentration to soil gas or groundwater concentration; sometimes used to estimate the indoor air concentration from soil gas or groundwater concentration. B Background Natural or baseline groundwater quality at a site that can be characterized by upgradient, historical, or sometimes cross-gradient water quality (Unified Guidance). Background (reference conditions) When used in sediment characterization studies, refers to both the concentrations of COPC that are not a result of the activities at the site undergoing assessment and the locations of the background areas (MacDonald and Ingersoll 2002). Therefore, there are two types of background recognized by USEPA and many states: naturally occurring background and anthropogenic background. Users should verify whether their state and/or USEPA region has different definitions and requirements for assessing background conditions as part of environmental site assessments. Bandwidth parameter A parameter in some regression models that helps fit the model to the sampled data. 4 February 2017 Bathymetry The measurement of or the information from water depth at various places in a body of water. Benthic habitat The benthic habitat is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some subsurface layers. Bentomats A reinforced geosynthetic clay liner (GCL) using sodium bentonite integrated into a geotextile matrix used in landfills, surface water impoundments and for secondary containment. Bioaccessible Describes the fraction of a chemical that desorbs from its matrix (such as soil, dust, or wood) in the gastrointestinal tract and is available for absorption. The bioaccessible fraction is not necessarily equal to the relative bioavailability but depends on the relation between results from a particular in vitro test system and an appropriate in vivo model. Bioaccumulation The accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost. Thus, the longer the biological half-life of the substance the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high. Bioaccumulation factor (BAF) The ratio of COPC in tissue to the COPC concentration in an external environmental phase (water, sediment, or food) (Spacie, Mccarty, and Rand 1995). The BAF is typically assumed to be measured or expressed on a steady-state basis. For applications to the water phase, the BAF is best determined from field data where sampled organisms are exposed to chemical measured in the water and their diet. For applications in reference to the ITRC- Contaminated Sediments Remediation August 2014 ITRC- Contaminated Sediments Remediation August 2014 496 sediment and food phases, the BAF is expressed using concentrations in the tissue and environmental phase on a wet weight basis or dry weight basis, for example, (µg/g of w/w tissue)/(µg/g of w/w food), (µg/g of d/w tissue)/(µg/g of d/w food), and (µg/g of d/w tissue)/(µg/g of d/w sediment). This definition of BAF is used for metals, organometallic compounds, and organic compounds. For clarity, the BAF is expressed with the units in subscripts. For the concentration