Glossary of Water Quality Definitions
ABSORPTION - The incorporation of a substance into the body of another.
ACIDITY - Having the properties of an acid; a pH less than 7.
ACTIVATED CARBON - Pure carbon heated to promote active sites which can adsorb pollutants, used in some water treatment systems to remove certain organic chemicals and radon gas.
ACUTE TOXICITY - As commonly used it is a pronounced effect, severe biological harm or death, produced in an organism by a toxicant, a substance or a mixture of substances within a short period of time, usually 96 hours or less, after exposure. The strict implication is simply one of rapid onset of effects, in comparison with the life span of the organism; severity is not necessarily implied. For algae and bacteria 96 hours would be a chronic exposure since it would last for several generations.
ADSORABLE ORGANIC HALIDES, AOX - The total of all halogenated organic compounds, particularly that are fluoridated, chlorinated or brominated.
ADSORPTION - The attachment or adhesion of a substance or chemicals generally on the surface of another solid material, adsorption is often used to extract pollutants by causing them to be attached to materials such as activated carbon.
ALGAE - A group of chlorophyll-containing, non-flowering plants, mostly aquatic, although many are planktonic, some species are extremely large.
ALGAL BLOOM - A bloom of algae occurs when their growth is so rapid that they become numerous enough to color a body of water, a population explosion of phytoplankton in response to changing environmental conditions, including eutrophication from wastewater and non-point sources, blooms can result in oxygen depletion and biological impacts such as fish kills, blooms are often the result of urban runoff of lawn fertilizers. Microcyctins can be produced in large quantities during algal blooms and pose a major threat to drinking and irrigation water supplies, as well as the environment at large. (see article Toxic Algal Bloom - Toledo, Ohio)
ALKALINE - Having a pH greater than 7, the measurement of constituents in a water supply which determine alkaline conditions, the alkalinity of water is a measure of its capacity to neutralize acids.
ALUM - An aluminum sulfate salt, generally potassium or ammonium is the cation, used to agglutinate particles in water treatment.
ANION - A negatively charged ion.
ANNELIDS - A phylum of segmented marine and freshwater worms, distinguished from non-segmented roundworms and flatworms,
ANOXIC WATERS - are areas of seas water, fresh water or ground water that are depleted of dissolved oxygen and have a more severe condition of hypoxia. The USGS defines anoxic waters as those with dissolved oxygen concentration of less than .5 mg per liter. Althought, anoxic waters are a natural phenomenon, and have occurred throughout geological history, recently, there have been some indications that eutrophication has increased the extent of the anoxic areas in areas including the Baltic Sea, the Gulf of Mexico and Hood Canal in Washington State. Eutrophication, an influx of nutrients (phosphate/nitrate), often a byproduct of agricultural run-off and sewage discharge, can result in large but short-lived algae blooms. Upon a bloom’s conclusion, the dead algae sink to the bottom and are broken down until all oxygen is expended. Such a case is the Gulf of Mexico where a seasonal dead zone occurs, which can be disturbed by weather patterns such as hurricanes and tropical convection. Sewage discharge, specifically that of nutrient concentrated “sludge”, can be especially damaging to ecosystem diversity. Species sensitive to anoxic conditions are replaced by fewer heartier species, reducing the overall variability of the effected area.
AOX, Adsorbable organic halides - The total of all halogenated organic compounds particularly those that are fluoridated, chlorinated or brominated.
Aquifer - Water within the soil or rocks beneath the surface of the earth that supplies wells and springs, water in the zone of saturation where all openings in rocks and soil are filled with water, the upper surface of which forms the water table, the streams or pools of water that flow or collect under the surface of the land and not on the surface, these may be confined if there are layers of impermeable material both above and below and it is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer, or unconfined when the upper water surface, the water table, is at atmospheric pressure, and is able to rise and fall, any geological formation containing or transmitting water, especially one that supplies the water for wells and springs, use of the term may be restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply.
Assimilative capacity - The amount of pollution a water body can receive without noticeable degradation, as a result of the natural ability of the water and its associated chemical and biological systems to dilute or transform contaminants.
Atmospheric deposition - The contribution of atmospheric pollutants or chemical constituents to land or water ecosystems, deposition results from materials in rain or snowfall, combined with dry dust fallout, atmospheric sources are a significant source of nutrients and contaminant to aquatic systems.