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Appendix F: Glossary

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.

bioaccessible. Describes the fraction of a chemical that desorbs from its matrix (e.g., soil, dust, 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 factor (BAF). The ratio of COPC in tissue to the COPC concentration in an external environmental phase (i.e., 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 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, i.e., (µg/g of ww tissue)/(µg/g of ww food), (µg/g of dw tissue)/(µg/g of dw food), and (µg/g of dw tissue)/(µg/g of dw 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 in the tissue phase, the numerator (N subscript) is the basis of the tissue phase (L for lipid-normalized, WW for wet weight, and DW for dry weight bases). For the environmental phase, the denominator (D subscript) is the basis for the water (FD for freely dissolved, T for total, and D for dissolved/filtered water), food (WW for wet weight and DW for dry weight), or sediment (WW for wet weight, and DW for dry weight) phases. Some commonly used BAF expressions are as follows:

bioavailability. The relationship between external (or applied) dose and internal (or resulting) dose of the chemical(s) being considered for an effect (NRC 2003).

bioavailability processes. Individual physical, chemical, and biological interactions that determine the exposure of plants and animals to chemicals associated with soils and sediments (NRC 2003).

bioconcentration factor. The ratio of the steady-state COPC concentration in an aquatic organism (CB) and the COPC concentration in water (CW) determined in a controlled laboratory experiment where the test organisms are exposed to chemical in the water (but not the diet). In the subscript, the numerator (N) is the basis of the tissue phase (L for lipid-normalized, WW for wet weight, and DW for dry weight bases) and denominator (D) is the basis for the water phase (FD for freely dissolved, T for total, and D for dissolved/filtered water). Commonly used BCF expressions are as follows:

biomagnification factor (field based). The ratio of the chemical concentrations in an aquatic or terrestrial organism (CB) and in the diet of the organism (CD) determined from field-collected animals that are exposed to chemical in air, water and diet. The numerator (N) is the basis of the tissue phase (L for lipid-normalized, WW for wet weight, and DW for dry weight bases) and denominator (D) is the basis for the diet (L for lipid-normalized, WW for wet weight, and DW for dry weight bases). Two commonly used BMF expressions are as follows:

biomagnification factor (laboratory based). The ratio of the steady-state chemical concentrations in an aquatic or terrestrial organism (CB) and in the diet of the organism (CD) determined in a controlled laboratory experiment, where the test organisms are exposed to chemical in the diet (but not water or air). In the subscript, the numerator (N) is the basis of the tissue phase (L for lipid-normalized, WW for wet weight, and DW for dry weight bases) and denominator (D) is the basis for the diet (L for lipid, WW for wet weight, and DW for dry weight bases). Commonly used BMF expressions are as follows:

biomimetic device. A diffusion-based sampler that is designed to “mimic” an aquatic organism (e.g., a semipermeable-membrane device is dialysis tubing filled with a purified fish oil like triolein).

biota sediment accumulation factor (BSAF, kg of organic carbon/kg of lipid). Ratio of the chemical concentration in an aquatic organism (CB, in g chemical/kg lipid) and in the sediment from the site where the organism was collected (CS, in g chemical/kg organic carbon) determined from field or laboratory data: BSAF = CB/CS.

bulk concentration. In water, the total COPC concentration in a bulk (unfiltered) sample of water (kg of COPC/L of water). In sediment, the total COPC concentration in a bulk sediment sample (kg COPC/kg dry sediment).

carbon normalization. For sediment, dividing a bulk organic COPC concentration (e.g., mg/kg fluoranthene) by the fraction of TOC measured in the same sample (e.g., 0.02 g carbon/ g sediment, or 2% TOC).

contaminant(s) of potential concern (COPC). In a risk assessment, a substance detected at a hazardous waste site that has the potential to affect receptors adversely due to its concentration, distribution, and mode of toxicity (USEPA 1997b). COPCs are generally categorized operationally, i.e., based on how they are measured in the analytical laboratory. “Inorganic” COPCs generally address metals, elements, and unique inorganic compounds such as perchlorate. “Organic” COPCs include VOCs (such as acetone, benzene, trichloroethylene, etc.), SVOCs (such as chlorophenols, chlorobenzenes, phthalate esters, etc.), pesticides (e.g., atrazine, DDT, toxaphene), PCBs, and polychlorinated dibenzodioxin and dibenzofurans.

diffusion sampler. A semipermeable membrane or dialysis tube filled with distilled water or gel, which relies on solute gradient to establish equilibrium between pore water and the sampler.

diffusive flux. A law describing the diffusion that occurs when solutions of different concentrations come into contact with molecules moving from regions of higher concentration to regions of lower concentration. Fick’s law states that the rate of diffusion dn/dt, called the “diffusive flux” and denoted J, across an area A is given by dn/dt = J = –DA∂c/∂x, where D is a constant called the “diffusion constant,” ∂c/∂x is the concentration gradient of the solute, and dn/dt is the amount of solute crossing the area A per unit time. D is constant for a specific solute and solvent at a specific temperature. Fick’s law was formulated by the German physiologist Adolf Eugen Fick (1829–1901) in 1855.

diffusive gradient in thin films (DGT). A sampler that is typically filled with a gel that is designed to target a specific compound (e.g., binding of metals).

dissolved concentration. In water, the concentration of COPC in filtered water, traditionally defined as water that will pass through a 0.45 µm filter.

epibenthic. On or above the sediment/water interface.

epifauna. Benthic invertebrates that live almost exclusively on or upon the benthic substrate. The substrate can range from soft silt or clay in a lentic environment to sand, gravel, pebbles, cobble and/or boulders in a lotic environment.

equilibrium partitioning theory. A theory developed in the late 1980s as a means of predicting toxicity of PAHs to sediment-dwelling organisms. It posits that the toxicity to sediment organisms is directly proportional to the amount of unbound PAH dissolved in sediment pore water.

final chronic value. See Section 4.1.3.2.

food-web magnification factor. See trophic magnification factor.

freely dissolved. The concentration of the chemical that is freely dissolved in water, excluding the portion sorbed onto particulate and dissolved organic carbon (kg of chemical/L of water). Freely dissolved concentrations can be estimated with an empirical equation with knowledge of the Kpoc and Kdoc and can be measured with passive samplers, e.g., POM, SPMD, SPME, and PE.

fugacity. A measure of a chemical potential in the form of “adjusted pressure.” It reflects the tendency of a substance to prefer one phase (liquid, solid, or gas) over another and can be literally defined as “the tendency to flee or escape.”

fugacity samplers. Polymeric materials inserted into sediment that accumulate hydrophobic organic compounds in proportion to their surface area.

gavage. Introduction of nutritive material into the stomach by means of a tube.

hyporheic zone. A region beneath and lateral to a stream bed, typically where there is an intermixing of shallow groundwater with surface water. This region is generally heterogeneous and difficult to define along the breadth and length of a stream.

infauna. Benthic invertebrates that live almost exclusively in or below the sediment/water interface. These are generally tube- or burrow-dwelling organisms that feed at either the sediment/water interface or burrow and ingest sediments and/or sediment-dwelling organisms.

ligand. Complexing chemical (ion, molecule, or molecular group) that interacts with a metal to form a larger complex (USEPA 2003a).

lipid-normalization. The COPC concentration in tissue (kg of chemical/kg of wet tissue) divided by the concentration of lipid in that tissue (kg of lipid/kg of wet tissue) or the COPC concentration in tissue (kg of chemical/kg of dry tissue) divided by the concentration of lipid in that tissue (kg of lipid/kg of dry tissue).

macroinvertebrate. Any organism that will, after sieving out surface water and fine suspended matter, be retained on a 0.5 mm mesh (No. 35 Standard Sieve) screen.

octanol-water partition coefficient (Kow, unitless). The ratio of a chemical concentration in 1‑octanol (Co) and water (Cw) in an octanol-water system that has reached a chemical equilibrium: Kow = Co/Cw.

organic carbon normalization. See Michelsen 1992.

pore water. Water located in the interstitial compartment (between solid-phase particles) of bulk sediment.

receptor. A plant, animal, or human that is typically the focus of a risk assessment following the direct or indirect exposure to a potentially toxic substance.

reference location (control). An aquatic sediment system unaffected by COPCs which can be used in a baseline comparison of like parameters in a similar contaminated system. See background.

resuspension flux. The movement of a contaminant through a liquid (or gaseous media) upon resuspension of contaminated sediments.

screening. The comparison (by ratio, usually the environmental medium concentration divided by a benchmark, standard, criterion, etc.) of site conditions to a screening value. Often this is synonymous with “compare to a list that is readily available.”

sediment quality guideline (SQG). Same as SQV except a guideline is typically issued by a regulatory agency or, in rare cases, promulgated via a state law.

sediment quality objective (SQO). Same as SQV and SQG in some state-specific standards and rules.

sediment quality value (SQV). A numerical (bulk concentration) benchmark below which a lesser adverse effect (or no adverse effect) is anticipated and above which a greater adverse effect is anticipated.

soil screening level. See “Regional Screening Table” at www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/index.htm.

stakeholder. Affected tribes, community members, members of environmental and community advocacy groups, and local governments.

sulfhydryl. Thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). Being the sulfur analogue of an alcohol group (-OH), this functional group is referred to either as a “thiol group” or a “sulfhydryl group.”

toxicity unit. A unit formerly synonymous with “minimum lethal dose” but which, because of the instability of toxins, is now measured in terms of the quantity of standard antitoxin with which a toxin combines. See www.biology-online.org/dictionary/Toxic_unit.

trophic magnification factor, or food-web magnification factor (TMF, or FWMF, unitless). The average factor by which the normalized chemical concentration in biota of a food web increases with each increase in trophic level. The TMF is determined from the slope (m) derived by plotting the logarithmically transformed (base 10) lipid-normalized chemical concentration in biota vs. the trophic position of the sampled biota (as TMF = 10m).

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