The penetration of atoms, ions, or molecules into the bulk mass of a substance.
- ACCEPTABLE INTAKE:
(for subchronic and chronic exposure): Numbers which describe how toxic a chemical is. The numbers are derived from animal studies of the relationship between dose and non-cancer effects. There are two types of acceptable exposure values: one for acute (relatively short-term) and one for chronic (longer-term) exposure.
A substance that has a pH of less than 7, which is neutral.
- ACTION LEVEL:
A guideline established by environmental protection agencies to identify the concentration of a substance in a particular medium (water, soil, etc.) that may present a health risk when exceeded. If contaminants are found at concentrations above their action levels, measures must be taken to decrease the contamination.
- ACTIVATED CARBON:
Carbon is “activated” to improve adsorption through a process that creates porous particles that have large internal surface areas.
- ACTIVATED SLUDGE:
A term used to describe sludge that contains microorganisms that break down organic contaminants (e.g., benzene) in liquid waste streams to simpler substances such as water and carbon dioxide.
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.
The process by which solutes are transported by the motion of flowing ground water.
- ADVISORY LEVEL:
Level above which an environmental protection agency suggests it is potentially harmful to be exposed to a contaminant, although no action is mandated.
- AERATION ZONE:
(See UNSATURATED ZONE)
For soils, a method of remediating contaminated soil by supplying or exposing the contaminated soil to air. The contaminants volatilize to the atmosphere. For water, the process of bubbling air through water or spraying water into the air to remove dissolved contaminants.
Any process that takes place in the presence of oxygen.
- AIR POLLUTION CONTROL DISTRICT (APCD):
Regulatory Agency charged with maintaining quality of air. Most air discharges from contaminated sites will require clearance of APCD.
- AIR SPARGING:
Method of removing VOC's (Volatile organic compounds) from ground water. Compressed air is forced through a well screen placed in the aquifer causing a bubbling effect in the groundwater. Contaminants in the groundwater are transferred to the air. These contaminants can then be removed by soil vapor extraction. Air sparging can enhance bioremediation.
- AIR STRIPPERS:
Equipment use in the process of mixing groundwater contaminated by petroleum with air. The mixing process removes the dissolved petroleum from the water by transferring it into the air. Local air pollution rules may prohibit or require permits for this method.
The total measurable bases (OH, HCO3, CO3) in a volume of water; a measure of a material's capacity to neutralize acids; pH > 7.
- ALL APPROPRIATE INQUIRY (AAI):
A federal rule published by the EPA in 2006 which establishes the environmental due diligence method to be followed by brownfield purchasers who wish to qualify for the Superfund liability relief provided by the Small Business Liability Relief and Brownfields Revitalization Act of 2001.
- ALLUVIAL DEPOSITS:
An area of sand, clay or other similar material that has been gradually deposited by moving water, such as along a river bed, on a delta, on a flood plain or at the base of a mountain.
- AMBIENT AIR:
Refers to the surrounding air. Generally, ambient air refers to air outside and surrounding an air pollution source location. Often used interchangeably with "outdoor air".
- AMBIENT WATER QUALITY:
Refers to the surrounding water. Generally, ambient water quality standards refers to the concentration of a toxic pollutant in a navigable water that, based on available data, will not result in adverse effects on important aquatic life, or on consumers of such aquatic life, after exposure for periods of time exceeding 96 hours and continuing at least through one reproductive cycle.
- AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM):
A professional research organization that sets standards for many services, including methods for sampling and testing of hazardous waste and media contaminated with hazardous waste.
Any process that occurs in the absence of oxygen.
- ANGLE DRILLING:
Instead of drilling vertically, drilling at an angle or a slant. Usually to investigate under buildings or other obstructions.
- APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENT:
Federal or state laws, regulations, standards, criteria or requirements which would apply to the cleanup of hazardous substances at a particular site.
Of, relating to, or resembling water.
A geologic formation(s) that is water bearing. A geological formation or structure that stores and/or transmits water, such as to wells and springs. Use of the term is usually restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people’s uses. Aquifer capacity is determined by the porosity of the subsurface material and its area. Under most of the United States, there are two major types of aquifers: confined and unconfined.
A gray, brittle and highly poisonous metal. It is used as an alloy for metals, especially lead and copper, and is used in insecticides and weed killers.
- ARTESIAN WATER:
Ground water that is under pressure when tapped by a well and is able to rise above the level at which it is first encountered. It may or may not flow out at ground level. For artesian conditions to exist, an aquifer must be overlain by a confining material and receive a supply of water. The pressure in such an aquifer commonly is called artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer.
- ARTIFICIAL RECHARGE:
A general name given a family of naturally occurring fibrous silicate minerals. Asbestos fibers were used mainly for insulation and as a fire retardant material in ship and building construction and other industries, and in brake shoes and pads for automobiles.
The reduction or lessening in amount (e.g., a reduction in the amount of contaminants in a plume as it migrates away from the source).
A tool used for drilling into unconsolidated earth materials (soil) consisting of a spiral blade wound around a central stem that is commonly hollow (hollow stem auger).
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