Valence state: The combining capacity of an atom or radical determined by the number of electrons that it will lose, add, or share when it reacts with other atoms.
free product: A NAPL found in the subsurface in sufficient quantity that it can be partially recovered by pumping or gravity drain.
aerobic: Direct aerobic metabolism involves microbial reactions that require oxygen to go forward. The bacteria uses a carbon substrate as the electron donor and oxygen as the electron acceptor. Degradation of contaminants that are susceptible to aerobic degradation but not anaerobic often ceases in the vicinity of the source zone because of oxygen depletion. This can sometimes be reversed by adding oxygen in the form of air (air sparging, bioventing), ozone, or slow oxygen release compound (e.g., ORC(r)).
Aerobic dechlorination may also occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal. For aerobic cometabolism to occur there must be sufficient oxygen and a suitable substrate which allows the microbe to produce the appropriate enzyme. These conditions may be present naturally but often in the presence of a source area oxygen and a substrate such as methane or propane will need to be introduced.
Adapted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites
anaerobic: Direct anaerobic metabolism involves microbial reactions occurring in the absence of oxygen and encompasses many processes, including fermentation, methanogenesis, reductive dechlorination, sulfate-reducing activities, and denitrification. Depending on the contaminant of concern, a subset of these activities may be cultivated. In anaerobic metabolism, nitrate, sulfate, carbon dioxide, oxidized metals, or organic compounds may replace oxygen as the electron acceptor.
Anaerobic dechlorination also may occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal.
Quoted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites
architecture: "Architecture" refers to the physical distribution of the contaminant in the subsurface. Residuals that take the form of long thin ganglia or small dispersed globules provide a larger surface area that will dissolve much faster than if the same amount of liquid were concentrated in a competent pool.
Sources: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.
source zone: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.
focal ulceration: The process or fact of a localized area being eroded away.
metaplasia of the glandular stomach: A change of cells to a form that does not normally occur in the tissue in which it is found.
hyperplasia of the glandular stomach: A condition in which there is an increase in the number of normal cells in a tissue or organ.
histiocytic: Degenerative.
duodenum: First part of the small intestine.
microcytic: Any abnormally small cell.
squamous cell papillomas: A small solid benign tumor with a clear-cut border that projects above the surrounding tissue.
squamous cell carcinomas: Cancer that begins in squamous cells-thin, flat cells that look under the microscope like fish scales. Squamous cells are found in the tissue that forms the surface of the skin, the lining of hollow organs of the body, and the passages of the respiratory and digestive tracts. Squamous cell carcinomas may arise in any of these tissues.
jejunum: The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum.
ileum: The distal and narrowest portion of the small intestine.
squamous: Flat cells that look like fish scales.
metaplasia: A condition in which there is a change of one adult cell type to another similar adult cell type.
ossification: The process of creating bone, that is of transforming cartilage (or fibrous tissue) into bone.
clastogenesis: Any process resulting in the breakage of chromosomes.
neoplastic: Abnormal and uncontrolled growth of cells.
ulceration: The process or fact of being eroded away.
leucocytosis: An elevation of the total number of white cells in blood.
neutrophils: A type of white blood cell.
chromodulin: A small protein that binds four trivalent chromium ions.
biomagnification: The increased accumulation and concentration of a contaminant at higher levels of the food chain; organisms higher on the food chain will have larger amounts of contaminants than those lower on the food chain, because the contaminants are not eliminated or broken down into other chemicals within the organisms.
exencephaly: Cerebral tissue herniation through a congenital or acquired defect in the skull.
everted viscera: Rotated body organs in the chest cavity.
To Be Considered: Documents, such as federal or state guidances, that are not legally binding but may be relevant to the topic in question.
gaining: A gaining surface water body is one where groundwater flows into it.
losing: A surface water body is losing when there is a permeable sediment bed that is not in contact with the groundwater allowing the surface water to seep through it.
fluvial: Of or pertaining to flow in rivers and streams.
lacustrine: Of or pertaining to a lake as in lacustrine sediments—sediments at the bottom of a lake.
lipid: Any class of fats that are insoluble in water.
lipophilic: Able to dissolve in lipids—in this case fatty tissue.
organelles: A part of a cell such as mitochondrion, vacuole, or chloroplast that plays a specific role in how the cell functions and membranes.
RfD: The RfD is an estimate of a daily exposure of the human population (including sensitive sub-groups) to a substance that is likely to be without "the appreciable risk of deleterious effects during a lifetime." An RfD is expressed in units of mg/kg-day.
autonomic: That part of the nervous system that controls non-conscious actions such as heart rate, perspiration and digestion.
ataxia: Lack of muscle coordination.
funnel-and-gate configuration: A system where low-permeability walls (the funnel) placed in the saturated zone direct contaminated ground-water toward a permeable treatment zone (the gate)
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Creosote is a combustible, yellowish, dark-green to brown or black liquid. It is made by fractional distillation of coal tar. Creosote consists of six major classes of compounds: aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs (which can constitute up to 90% of creosote); tar acids/phenolics; tar bases/nitrogen-containing heterocycles; aromatic amines; sulfur-containing heterocycles; and oxygen-containing heterocycles, including dibenzofurans (IPCS 2004). The composition of the mixture varies among lots and across manufacturers.
Many of creosote's chemical and physical properties reflect those of the individual compounds that form the mixture. Some of these compounds are soluble while others are not. Although the main components of creosote are naphthalene and its alkyl derivatives, phenanthrene, fluorene, acenaphthene, alkylphenols, and dibenzofuran, the more soluble components (benzene, toluene, ethylbenzene, xylenes, nitrogen-containing heterocycles, sulfur-containing heterocycles, and phenolics) are generally present at a much higher percentages in leachate and contaminated water (IPCS 2004). As creosote ages, the more volatile and soluble components of the mixture diminish relative to the less volatile and soluble compounds. Aging also affects mobility since the heavier components have higher Koc values and tend to sorb to soil more than the lighter molecules (the log organic carbon sorption coefficient (Koc) for PAHs ranges from 2.4 to 7.0 (IPCS 1998)).
Various hazardous materials data sheets show specific gravity values between 1.03 and 1.18, or very slightly heavier than water. However, the reported range can vary more because products sold as creosote may be altered according to the application needed. For instance, blending lighter hydrocarbons, such as diesel, with creosote cuts the cost and improves penetrating ability. Adding heavier coal tar pitch to creosote increases viscosity.
When spilled on the ground, the vapor pressure of the individual compounds affects the fate of the creosote. The vapor pressures of individual components detected in creosote range from 12,700 Pa for benzene to 2.0 x 10-10 Pa for dibenzo[a,h]anthracene. Generally, low-molecular-weight PAHs (e.g., naphthalene, anthracene, and phenanthrene) are mainly in the gas phase, and high-molecular-weight PAHs are mainly bound to particles. Phenolic compounds, including cresols, as well as the heterocyclic fraction tend to be in the vapor state. However, it is not clear how the specific composition of creosote modifies the distribution behavior of the individual components (IPCS 2004).
Although the transport of creosote compounds from water surfaces to air depends on their individual volatilization rates, volatilization is not considered a dominant process for PAHs and cresols (IPCS 2004).
Generally, the high molecular-weight aromatic organic compounds (more than three rings), with relatively low solubilities and high adsorptive capacities, dominate in sediment, whereas the low molecular-weight aromatic organic compounds (fewer than three aromatic rings) partition selectively into the aqueous phase (IPCS 2004).
The log organic carbon sorption coefficient (Koc) values for PAHs, which range from 2.4 to 7.0 (IPCS 1998), indicate moderate to minimal mobility in the subsurface. The log Kow for creosote is 1. Some components of creosote are expected to bioaccumulate.
Creosotes are more likely to degrade under aerobic than anaerobic conditions. The degradation rates are compound-specific with the heavier PAHs being very recalcitrant.
This document contains a thorough discussion of the physical and chemical properties of coal tar creosote, its fate and transport, and human health effects.
This profile covers coal tar creosote human health effects, chemical and physical properties, manufacturing volume data, potential for human exposure (environmental fate and transport), and analytical methods.
Toxicological Profile for Wood Creosote, Coal Tar Creosote, Coal Tar, Coal Tar Pitch, and Coal Tar Pitch Volatiles 
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