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- absorption
- The process by which one substance draws into itself another substance. Example: a sponge picking up water; an oil absorbent pulling in petroleum products. Compare with adsorption.
- acid
- A substance that donates hydrogen ions that can be accepted by a base. Acids have a pH below 7. Contrast with base.
- acute
- Acute health effects usually develop rapidly after a short-term exposure to hazardous chemicals. Acute effects have a short duration. Contrast with chronic.
- adsorption
- The process by which one substance is attracted to and adheres to the surface of another substance without actually penetrating its internal structure. Compare with absorption.
- AEGL
- Acute Exposure Guideline Level, a level of concern representing the adverse health effects of a hazardous substance on members of the general public. The AEGLs are developed by the National Research Council's National Advisory Committee on AEGLs (www.epa.gov/oppt/aegl).
- aerial observation
- Viewing a spill from a helicopter, fixed-wing aircraft, or vessel to assess the character and extent of pollutant spilled on the water. See also overflight.
- aerobic
- Living, growing, and reproducing in an environment with air or oxygen present (e.g., aerobic bacteria). Contrast with anaerobic.
- aerosol
- Fine liquid droplets (or solid particles) suspended in a gas.
- air-reactive
- Likely to react rapidly or violently with dry air or moist air; may generate toxic and corrosive fumes upon exposure to air, or may catch fire.
- AIS
- Automatic Identification System. A system used by ships and vessel traffic systems for identifying vessels at sea, particularly when the ships are not in sight (e.g., at night, in fog, in radar blind arcs or shadows, or at distance). AIS provides a means for ships to exchange ID, position, course, speed, and other data with all other nearby ships and vessel traffic system stations.
- alkali
- A general description given to strong bases, including the hydroxides and carbonates of the "alkali metal" or group 1A of the Periodic Table. Examples include sodium hydroxide and potassium hydroxide. A synonym for the strong alkalis is caustics.
- alkaline
- Having a high concentration of hydroxide ions in aqueous solution (i.e., a pH greater than 7). Strongly alkaline aqueous solutions are very corrosive to skin, metal, and other materials. See also base.
- allision
- A "crash" of a vessel with an fixed object. Contrast with collision.
- ALOHA
- Computer model that predicts the area potentially affected by a toxic gas release, fire, or explosion; ALOHA is a component of the CAMEO software suite. Find out more about ALOHA on the NOAA OR&R website (response.restoration.noaa.gov/aloha).
- ambient temperature and pressure
- Typical outdoor temperature and pressure.
- anadromous
- Fish that spend most of their life in saltwater but migrate to freshwater to spawn (breed and lay eggs). Examples include salmon, river herring (alewife), and striped bass. Contrast with catadromous.
- anaerobic
- Living, growing, and reproducing in an environment without air or oxygen (e.g., anaerobic bacteria). Contrast with aerobic.
- ANFO
- Ammonium nitrate-fuel oil mixtures used in commercial explosives.
- anhydrous
- Lit. "without water." A chemical shipped or stored without water, rather than in solution, is in anhydrous form (anhydrous ammonia is a common example).
- anthropogenic
- Having to do with or caused by humans.
- API
- American Petroleum Institute (www.api.org). A national trade association that represents all aspects of the U.S. oil and natural gas industry, from exploration through marketing.
- API gravity
- The density of petroleum liquids expressed in degrees according to an American Petroleum Institute (API) recommended scale. The measuring scale is calibrated in terms of degrees API. The higher the API gravity, the lower the density of the compound. Crude oil is classified as light, medium or heavy, according to its measured API gravity. API gravity is dependent on temperature and barometric pressure, and therefore generally is measured at 16° C and 1 atmospheric pressure. Oils with low specific gravity have high API gravity and vice versa. API specific gravity can be calculated using the following formula: API Gravity = (141.5/Specific gravity at 16° C) - 131.5.
- aqueous
- In an aqueous solution, a substance is dissolved in water.
- ARD
- See Assessment and Restoration Division.
- aromatic hydrocarbons
- Hydrocarbons characterized by unsaturated ring structures of the carbon atoms. Commercial petroleum aromatics are benzene, toluene and xylenes. Aromatics are the heaviest, have the highest boiling points and are the most toxic of the crudes.
- asphalt
- Thick, viscous, petroleum-based mixture used to surface roads, for roofing, and in other products.
- asphyxiant
- Can cause unconsciousness or death by displacing oxygen from the air; especially dangerous in confined spaces.
- assessment
- See Natural Resource Damage Assessment.
- Assessment and Restoration Division (ARD)
- A division of NOAA's Office of Response and Restoration (OR&R) that works to protect and restore coastal natural resources injured by hazardous substances, such as waste sites, oil and chemical spills, and ship groundings. Formerly the Coastal Protection and Restoration Division (CPRD).
- Atlantic Intracoastal Waterway
- The portion of the Intracoastal Waterway located along the Atlantic coast of the U.S. It is a navigable inland waterway extending from Key West, Florida to Boston, Massachusetts. See also Intracoastal Waterway.
- ATSDR
- Agency for Toxic Substances and Disease Registry (www.atsdr.cdc.gov). Federal public health agency that provides health information related to toxic substances.
- autoignition temperature
- Minimum temperature at which a substance ignites when no ignition source (e.g., spark or flame) is present.
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