Acronyms or jump to Glossary of Terms

CERCLA - Comprehensive Environmental Responsibility, Compensation and Liability Act of 1980. Also known as the Federal "Superfund" Act, the federal legislation that addresses cleanup of the nation's major hazardous wastes sites.

DNAPL – Dense Non-Aqueous Phase Liquid, a liquid that is denser than water and does not dissolve or mix easily in water. In the presence of water it forms a separate phase from the water. DNAPLs tend to "sink" and accumulate as a separate phase below the water table and be a long-term source of groundwater contamination. DNAPLs are often difficult to locate and remediate. Many chlorinated solvents, such as trichloroethylene, are DNAPLs.

DRE - Destruction and Removal Efficiency – a term used to express the fraction or percentage reduction of a compound from a contaminated stream while passing through a treatment process. In soil vapor extraction systems, it is the percentage of volatile organic emissions destroyed or removed from the extracted soil gas stream by the emissions control equipment.

EPA TCLP – the U.S. Environmental Protection Agency Toxicity Characteristic Leaching Procedure (TCLP). A test that is performed to determine the mobility and availability of contaminants to dissolve and migrate. The TCLP test is applicable to wastes containing certain listed contaminants. Wastes failing the TCLP test are considered toxic and must be managed as hazardous wastes.

GAC - Granulated Activated Carbon - a commonly used carbon-based adsorbent used to remove compounds, primarily organic in nature, from air or liquid stream

HAPs – Hazardous air pollutants.

ppb – parts per billion. An expression of the concentration of a substance, typically used for solutions or solids. A concentration of 1 ppb would mean that the substance makes up one billionth of the mass of the sample.

ppb_v – parts per billion by volume. A similar concept as "ppb" but commonly applied to a gas so that 1 ppb_v would mean that the substance occupies one billionth of the volume of a gas sample.

ppm – parts per million. An expression of the concentration of a substance, typically used for solutions or solids. A concentration of 1 ppm would mean that the substance makes up one millionth of the mass of the sample

ppm_v – parts per million by volume. A similar concept as "ppm" but commonly applied to a gas so that 1 ppm_v would mean that the substance occupies one millionth of the volume of a gas sample.

PICs – products of incomplete combustion. Those chemicals remaining in the effluent gases that are not carbon dioxide, water or acids such as hydrochloric or sulfuric acids. Examples would be carbon monoxide (CO), other unburned hydrocarbons and trace species such as chlorinated dioxins and furans.

NETTS - National Environmental Technology Test Site – A site established by the U.S. Department of Defense where new and innovative site cleanup technologies can be field tested and demonstrated, for example McClellan Air Force Base and the Naval Facilities Engineering Service Center at Port Hueneme have served in that capacity.

RAP - Remedial Action Plan – the remedy selection document for a contaminated site that is prepared after the RIFS and, if the cost of cleanup will be greater than $1 million.

RAW - Removal Action Workplan – the remedy selection document for a contaminated site that is prepared after the RIFS and, if the cost of cleanup will be less than $1 million.

RIFS - Remedial Investigation and Feasibility Study – one of the steps in the clean-up process: a full-fledged evaluation of the property to determine what hazardous substances are present, the level of contamination and risk, and the lateral and vertical extent of contamination.

SERDP - Strategic Environmental Research and Development Program – a federal program involving the Department of Energy, U.S. Environmental Protection Agency and the Department of Defense in development of new environmental technologies.

SVOC – Semi-Volatile Organic Compounds - SVOCs are organic compounds that can vaporize slowly at ambient temperatures. Some SVOCs have adverse, chronic and acute health effects, such as naphthalene, once a common ingredient of mothballs that has been replaced by dichlorobenzene (also an SVOC) in some types of mothballs that are still in use today. The plug-in types of air fresheners used in homes are also examples of SVOCs. Sources of SVOCs include motor vehicle exhaust, waste burning, industrial and consumer products, pesticides, industrial processes, and soil vapor extraction among others.

TEF - Toxic Equivalency Factor - factors that compare the relative toxicity of each dioxin and dioxin-like compound to the toxicity of the most highly studied dibenzo-p-dioxin, 2,3,7,8-TCDD. These factors or TEFs are used to calculate the toxicity equivalence or TEQ of a mixture of “dioxins,” which is the amount of 2,3,7,8-TCDD it would take to equal the combined toxic effect of all the “dioxins” and “dioxin-like” compounds found in the mixture.

TEQ - Toxicity Equivalent – Toxicity Equivalence or TEQ is used to express the total toxicity of a mixture of “dioxins” and “furans” in terms of the amount of 2,3,7,8-TCDD it would take to equal the combined toxic effect of all the “dioxins” and “furans” found in the mixture. Toxicity Equivalency Factors developed for each compound in the mixture are used to calculate the TEQ. (See TEF).

VOC - Volatile Organic Compounds - VOCs are organic compounds that can vaporize easily at ambient temperatures. Some VOCs are highly reactive and play a critical role in the formation of ozone. Other VOCs have adverse, chronic, and acute health effects. In some cases, VOCs can be both highly reactive and potentially toxic. Sources of VOCs include motor vehicle exhaust, waste burning, gasoline marketing, industrial and consumer products, pesticides, industrial processes, degreasing operations, pharmaceutical manufacturing, dry cleaning operations and soil vapor extraction.

Glossary of Terms

adsorption – a process by which certain molecules adsorb or stick to the surface of the "adsorbent" and are removed from a liquid or gas stream. Examples of common adsorbents are activated carbon, natural and artificial zeolites and specially designed polymeric materials.

byproducts - during any chemical or biologically mediated reaction, products are formed that are not the primary compound desired. These are termed byproducts and the byproducts may or may not produce adverse effects. The dioxins and furans are examples of byproducts that may be formed in trace quantities by combustion processes where chlorine or bromine is present in the stream.

cumulative effects – in the context of this web site, a term referring to the successive effects resulting from multiple exposures to a single compound or combined exposure of different compounds.

catalytic oxidation – oxidation of an organic compound that is enabled to occur at a significant rate with the aid of a catalyst. This typically involves thermal oxidation of a compound without the presence of a "flame" and occurs at lower temperature than that required to sustain a "flame."

catalyst - a compound which reduces the energy required to activate a reaction and thereby allows a reaction to proceed at significant rates at lower energy, i.e., typically lower temperature.

condensate – the liquid that forms when a vapor is cooled, e.g., dew formation from water vapor in the atmosphere.

cometabolic or cometabolism - refers to the biodegradation of a pollutant by a microorganism while using some other compound(s) for growth and energy. The microorganism cannot grow on the pollutant alone, and derives little or no benefit from the degradation of the pollutant.

dioxins – the commonly used term for polychlorinated dibenzo-p-dioxins (PCDDs), a group of chlorinated compounds with similar chemical structure that are toxic and persistent in the environment. The term dioxin is also used for the most well-studied and one of the most toxic dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). Although not strictly correct, the term “dioxins” is sometimes used to refer to all dioxins and dioxin-like compounds, including dibenzofurans and PCBs. The toxicity of other dioxin and dioxin-like molecules with different numbers of chlorine or bromine atoms and in different locations on the ring structure are expressed in terms of their "equivalent" effect to 2,3,7,8- tetrachlorodibenzo-p-dioxin. (See figure below for structure.)

dibenzofurans - A class of chemical compounds having a specific chemical structure similar to that of dioxins. The 2,3,7,8-tetrachlorodibenzofuran isomer has one less oxygen atom than the dibenzodioxin. The potency of the chlorinated dibenzofurans is expressed in terms of toxic equivalents (TEQ).

fixed film – in the context of this web site, referring to a biofilm supported on a stationary medium, e.g., biofilms attached to the surface of particles in a bed of compost or a biofilm attached to rocks in a flowing stream.

fluidized bed – a bed of particles that is suspended by moving a fluid such as air or water through it.

illumination factors – in the context of this web site, a technical term for the amount of light radiation effectively available for to produce photolytic reactions.

microgram (mg) – a millionth of one gram (a dime has a mass of a little more than 2 grams).

non-thermal plasma – a plasma that is generated by means other than application of heat (see plasma)

picogram (pg) – one million of a one microgram (a dime has a mass of a little more than 2 grams)

photolytic – derived from the terms "photo" and "lysis", meaning to disintegrate or break apart with the radiation energy of light.

photocatalytic – a reaction that is catalyzed by the presence of the radiation energy of light.

photocatalyic oxidation - A chemical reaction involving the oxidation of organic compounds in the presence of a catalyst and ultraviolet (UV) or visible light. The catalyst produces strong oxidizing radicals when activated by UV light. Volatile organic compounds adsorbed onto the catalyst are oxidized into (primarily) carbon dioxide (CO₂) and water. The treatment of chlorinated organics also produces hydrochloric acid.

picogram (pg) - one trillionth of a gram or one millionth of one microgram.

plasma – An electrically neutral, highly ionized gas composed of ions, electrons, and neutral particles. It is a phase of matter distinct from solids, liquids, and normal gases. A plasma is an excellent conductor and is influenced by magnetic and electric fields. An example of plasma is the atmosphere in a lighted fluorescent bulb.

sensitive receptor – typically used in the context of sensitive human populations that have the potential to be exposed to emissions, and that may be at greater risk of an adverse effect from exposure to a contaminant. More specifically in the context of modeling risk assessments for airborne contaminants, those locations where populations of individuals that may be more sensitive than the general public are located, for example, a school that children attend, a daycare center, a hospital or a convalescent home.

stakeholder – a party that has a vested interest in the outcome of a process. In the context of SVE, decisions regarding whether to treat and with what technology and monitoring would be of interest to stakeholders. Thus examples of stakeholders would be a community member living near the contaminated site, a regulator with management responsibility for the site, a business whose property is being treated, etc.

thermal oxidation – a term commonly used for the reaction of organic compounds with oxygen at elevated temperature. Examples of a thermal oxidation process would be a rotary kiln incinerator, a fume incinerator, or a flare. An common household example of a thermal oxidation process not involving a flame would be an electrically heated "self-cleaning" oven.

vadose zone – the region of the subsurface including the soil horizon and underlying formation that is not saturated with water, i.e., the region above the water table to the surface.

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