| OCR Text |
Show Glossary Algae- Chlorophyll- bearing nonvascular, primarily aquatic species that have no true roots, stems, or leaves; most algae are microscopic, but some species can be as large as vascular plants. Aquatic- life guidelines- Water- quality guidelines for protection of aquatic life. Often refers to U. S. Environmental Protection Agency water- quality criteria for protection of aquatic organisms. Aquifer- A water- bearing layer of soil, sand, gravel, or rock that will yield usable quantities of water to a well. Atmospheric deposition- The transfer of substances from the air to the surface of the Earth, either in wet form ( rain, fog, snow, dew, frost, hail) or in dry form ( gases, aerosols, particles). Background concentration- A concentration of a substance in a particular environment that is indicative of minimal influence by human ( anthropogenic) sources. B i ota- Living organisms. Chlorofluorocarbons- A class of volatile compounds consisting of carbon, chlorine, and fluorine. Commonly called freons, which have been used in refrigeration mechanisms, as blowing agents in the fabrication of flexible and rigid foams, and, until several years ago, as propellants in spray cans. Community- In ecology, the species that interact in a common area. Concentration- The amount or mass of a substance present in a given volume or mass of sample. Confined aquifer ( artesian aquifer)- An aquifer that is completely filled with water under pressure and that is overlain by material that restricts the movement of water. Confining layer- A layer of sediment or lithologic unit of low permeability that bounds an aquifer. Confluence- The flowing together of two or more streams; the place where a tributary joins the main stream. DDT- Dichloro- diphenyl- trichloroethane. An organochlorine insecticide no longer registered for use in the United States. Degradation products- Compounds resulting from transformation of an organic substance through chemical, photochemical, and/ or biochemical reactions. Dissolved solids- Amount of minerals, such as salt, that are dissolved in water; amount of dissolved solids is an indicator of salinity or hardness. Drinking- water standard or guideline- A threshold concentration in a public drinking- water supply, designed to protect human health. As defined here, standards are U. S. Environmental Protection Agency regulations that specify the maximum contamination levels for public water systems required to protect the public welfare; guidelines have no regulatory status and are issued in an advisory capacity. Ecoregion- An area of similar climate, landform, soil, potential natural vegetation, hydrology, or other ecologically relevant variables. Eutrophication- The process by which water becomes enriched with plant nutrients, most commonly phosphorus and nitrogen. Habitat- The part of the physical environment where plants and animals live. Invertebrate- An animal having no backbone or spinal column. Major ions- Constituents commonly present in concentrations exceeding 1.0 milligram per liter. Dissolved cations generally are calcium, magnesium, sodium, and potassium; the major anions are sulfate, chloride, fluoride, nitrate, and those contributing to alkalinity, most generally assumed to be bicarbonate and carbonate. Median- The middle or central value in a distribution of data ranked in order of magnitude. The median is also known as the 50th percentile. Micrograms per liter ( pg/ L)- A unit expressing the concentration of constituents in solution as weight ( micrograms) of solute per unit volume ( liter) of water; equivalent to one part per billion in most stream water and ground water. One thousand micrograms per liter equals 1 mg/ L. Midge- A small fly in the family Chironomidae. The larval ( juvenile) life stages are aquatic. Milligrams per liter ( mg/ L)- A unit expressing the concentration of chemical constituents in solution as weight ( milligrams) of solute per unit volume ( liter) of water; equivalent to one part per million in most stream water and ground water. One thousand micrograms per liter equals 1 mg/ L. Nitrate- An ion consisting of nitrogen and oxygen ( N03"). Nitrate is a plant nutrient and is very mobile in soils. Nonpoint source- A pollution source that cannot be defined as originating from discrete points such as pipe discharge. Areas of fertilizer and pesticide applications, atmospheric deposition, manure, and natural inputs from plants and trees are types of nonpoint source pollution. Nutrient- Element or compound essential for animal and plant growth. Common nutrients in fertilizer include nitrogen, phosphorus, and potassium. Organochlorine compound- Synthetic organic compounds containing chlorine. As generally used, term refers to compounds containing mostly or exclusively carbon, hydrogen, and chlorine. Examples include organochlorine insecticides, |
