| Abiotic |
| Pertaining to factors or things that are separate and independent from living things; nonliving. |
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| Abiotic factors Nonliving |
| Components of the ecosystem, including chemical and physical factors such as availability of nitrogen, temperature, and rainfall. |
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| Abortion |
| The termination of a pregnancy by some form of surgical or medicinal intervention. |
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| Absolute poverty |
| The lack of sufficient income in cash or exchange items for meeting the most basic human needs for food, clothing, and shelter. |
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| Abundance |
| The number or amount of something. |
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| Accelerated erosion |
| Loss of soil due to wind or water in land disturbed by human activities. |
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| Accelerated extinction |
| Elimination of species due to human activities such as habitat destruction, commercial hunting, sport hunting, and pollution. |
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| Acid |
| Any compound that releases hydrogen ions when dissolved in water. Also, a water solution that contains a surplus of hydrogen ions. |
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| Acid deposition |
| Rain or snow that has a lower p1-I than precipitation from unpolluted skies, also includes dry forms of deposition such as nitrate and sulfate particles. |
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| Acid mine drainage |
| Sulfuric acid that drains from mines, especially abandoned underground coal mines in the East (Appalachia). Created by the chemical reaction between oxygen,water, and iron sulfides found in coal and surrounding rocks. |
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| Acid precipitation |
| Acidic rain, snow, or dry particles deposited from the air due to increased acids released by anthropogenic or natural resources. |
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| Activated sludge |
| Sludge made up of clumps of living organisms feeding on detritus that settles out and is recycled in the process of secondary wastewater treatment. |
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| Activated sludge system |
| A system for removing organic wastes from water. The system uses microorganisms and active aeration to decompose such wastes. The system is used most as a means of secondary sewage treatment following the primary settling of materials. |
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| Active safety features |
| Those safety features of nuclear reactors that rely on operator-controlled reactions, external power sources, and other features that are capable of failing. (See passive safety features.) |
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| Active solar |
| Capturing and storage of the sun's energy through special collection devices (solar panels) that absorb heat and transfer it to air, water, or some other medium, which is then pumped to a storage site (usually a water tank) for later use. Contrast with passive solar. |
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| Active solar system |
| A mechanical system that actively collects, concentrates, and stores solar energy. |
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| Actual risk |
| An accurate measure of the hazard posed by a certain technology or action. |
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| Acute |
| A sudden, dramatic reaction to exposure to a toxin or other dangerous factor. |
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| Acute effects |
| In general, effects that occur shortly after exposure to toxic agents. Contrast with chronic effects. |
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| Acute poverty |
| Insufficient income or access to resources needed to provide the basic necessities for Life such as food, shelter, sanitation, clean water, medical care, and education. |
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| Acute toxicity |
| Poisoning generally caused by short-term exposure to high levels of one or more agents. Symptoms appear soon after exposure. |
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| Adaptation |
| A genetically determined structural or functional characteristic of an organism that enhances its chances of reproducing and passing on its genes. |
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| Adaptive radiation |
| Evolution of several life forms from a common ancestor. |
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| Adiabatic cooling |
| The cooling that occurs when warm air rises and encounters lower atmospheric pressure. Adiabatic warming is the opposite process, where cool air descends into higher pressure. |
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| Adsorption |
| The process whereby chemicals (ions or molecules) stick to the surface of other materials. |
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| Advanced industrial society |
| Post-World War II industrial society characterized by great rises in production and consumption, increased energy demand, and a shift toward synthetics and nonrenewable resources. |
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| Aeration |
| Soil: The exchange within the soil of oxygen and carbon dioxide necessary for the respiration of roots. Water: The bubbling of air or oxygen through water to increase the dissolved oxygen. |
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| Aerosols |
| Minute particles or liquid droplets suspended in the air. |
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| Aesthetic degradation |
| Changes in environmental quality that offend our aesthetic senses. |
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| Affluenza |
| A term used to describe a dysfunctional relationship with wealth or money. |
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| Age structure |
| Within a population, proportions of people who are old, middle-aged, young adults, and children. |
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| Agenda 21 |
| A definitive program to promote sustainable development that was produced by the 1992 Earth Summit in Rio de Janeiro, Brazil, and adopted by the U.N. General Assembly. |
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| Age-specific fertility rate |
| Number of live births per 1000 women of a specific age group. |
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| Agricultural land conversion |
| Transformation of farmland to other purposes, primarily cities, highways, airports, and the like. |
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| Agricultural society |
| A group of people living in villages or towns and relying on domestic animals and crops grown in nearby fields. Characterized by specialization of work roles. |
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| AIDS |
| Acquired immune deficiency syndrome, a fatal disease caused by the HIV (human immunodeficiency virus) and transmitted by sexual contact or the use of nonsterile needles (as in drug addiction). |
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| Air pollution disaster |
| Short-term situation in industrial cities in which intense industrial smog brings about a significant increase in human mortality. |
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| Air toxics |
| A category of air pollutants including radioactive materials and other toxic chemicals that are present at low concentrations but are of concern because they often are carcinogenic. |
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| Albedo |
| A description of a surface𠏋 reflective properties. |
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| Alga, pl. algae |
| Any of numerous kinds of photosynthetic plants that live and reproduce entirely immersed in water. Many species, the planktonic forms, exist as single or small groups of cells that float freely in the water. Other species, the 𦽳eaweeds,?may be large and attached. |
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| Algal bloom |
| Rapid growth of algae in surface waters due to increase in inorganic nutrients, usually either nitrogen or phosphorus. |
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| Alien species (or foreign species) |
| Any species introduced into or living in a new habitat. Also known as an exotic. |
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| Alkaline, alkalinity |
| A basic substance; chemically, a substance that absorbs hydrogen ions or releases hvdroxvl ions; in reference to natural water, a measure of the base content of the water. |
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| Alleles |
| The two or more variations of a gene for any particular characteristic, e.g., blue and brown are alleles of the gene for eye color. |
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| Allergens |
| Substances that activate the immune system and cause an allergic response; may not be directly antigenic themselves but may make other materials antigenic. |
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| Alley cropping |
| Agricultural cropping in which rows of shade-producing trees are alternated with rows of food crops to promote growth in dry climates. |
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| Alpha particles |
| Positively charged particles consisting of two protons and two neutrons, emitted from radioactive nuclei. |
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| Alpine |
| The high, treeless biogeographic zone of mountains that consists of slopes above the timberline. |
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| Altruistic preservation |
| A philosophy of preserving nature for its own sake. |
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| Alveoli |
| Small sacs in the lungs where exchange of oxygen and carbon dioxide between air and blood occurs. |
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| Ambient air |
| The air immediately around us. |
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| Ambient air quality standard |
| Maximum permissible concentration of a pollutant in the air around us. Contrast with emissions standard. |
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| Ambient standards |
| Air-quality standards (set by the EPA) stating that outside average air should always maintain a level of purity. That is, certain levels of pollution should not be exceeded in order to maintain environmental and human health. |
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| Amino acid |
| An organic compound containing an amino group and a carboxyl group; amino acids are the units or building blocks that make peptide and protein molecules. |
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| Ammuals |
| Plants that grow from seeds, for example, domestic corn and radishes. |
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| Anaerobic |
| Oxygen-free. |
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| Anaerobic digestion |
| The breakdown of organic material by microorganisms in the absence of oxygen. The process results in the release of methane gas as a waste product. |
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| Anaerobic respiration |
| The incomplete intracellular breakdown of sugar or other organic compounds in the absence of oxygen that releases some energy and produces organic acids and/or alcohol. |
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| Anemia |
| Low levels of hemoglobin due to iron deficiency or lack of red blood cells. |
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| Animal testing |
| Procedures used to assess the toxicity of chemical substances using rats, mice and guinea pigs as surrogates for humans who might be exposed to the substances. |
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| Annual |
| A plant that lives for a single growing season. |
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| Antagonism |
| In toxicology, when two chemical or physical agents (often toxins) counteract each other to produce a lesser response than would be expected if individual effects were added together. |
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| Anthropocentric |
| The belief that humans hold a special place in nature; being centered primarily on humans and human affairs. |
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| Anthropogenic |
| Referring to pollutants and other forms of impacts on natural environments that can be traced to human activities. |
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| Anthropogenic hazard |
| A danger created by humans. |
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| Antigens |
| Substances that stimulate the production of, and react with, specific antibodies. |
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| Appropriate technology |
| A term coined by the late E. F. Schumacher to refer to technology that is "appropriate" for the economy, resources and culture of a region. It is characterized by small to medium sized machines, maximum human labor, ease of understanding , meaningful empolyment, use of local resources, adecentralized production, production of durable products, emphasis on renewable resources, especially energy, and compatibility with the environment and culture. |
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| Aquaculture |
| Cultivation of fish and other aquatic organisms in freshwater ponds, lakes, irrigation ditches, and other bodies of water. |
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| Aquifer |
| Underground stratum of porous material (sandstone) containing water (groundwater), which may be withdrawn from wells for human use. |
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| Aquifer recharge zone |
| Region in which water from rain or snow percolates into an aquifer, replenishing the supply of groundwater. |
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| Aquifers |
| Porous, water-bearing layers of sand, gravel, and rock below the earth𠏋 surface; reservoirs for groundwater. |
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| Arithmetic growth |
| A pattern of growth that increases at a constant amount per unit time, such as 1, 2, 3, 4 or 1, 3, 5, 7. |
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| Artesian well |
| The result of a pressurized aquifer intersecting the surface or being penetrated by a pipe or conduit, from which water gushes without being pumped; also called a spring. |
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| Artificial selection |
| Selective breeding to create new plant and animal breeds to bring out desirable characteristics. |
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| Asbestos |
| One of several naturally occurring silicate fibers. Use ful in society as an insulator but deadly to breathe even in small amounts. Causes mesothelioma, asbestosis, and lung cancer. |
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| Asbestos fibers |
| Crystals of asbestos, a natural mineral, that have the form of minute strands; asbestos is a serious health hazard in indoor spaces. |
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| Asbestosis |
| Lung disease characterized by buildup of scar tissue in the lungs. Caused by inhalation of asbestos. |
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| Asphyxiants |
| Chemicals that exclude oxygen or actively interfere with oxygen uptake and distribution; includes inert chemicals, such as nitrogen gas or halothane, that can displace oxygen and fill enclosed spaces. |
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| Asthma |
| Lung disorder characterized by constriction and excessive mucus production in the bronchioles, resulting in periodic difficulty in breathing, shortness of breath, coughing. Usually caused by allergy and often aggravated by air pollution. |
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| Atmosphere |
| Layer of air surrounding the earth. |
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| Atmospheric deposition |
| Sedimentation of solids, liquids, or gaseous materials from the air. Snow, rain, and dust are the most familiar examples, but acids, metals, and toxic organic chemicals also can be transported by winds and deposited far from the source of origin. |
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| Atom |
| A basic unit of matter consisting of a nucleus of positively charged protons and uncharged neutrons, and an outer cloud of electrons orbiting the nucleus. |
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| Atomic number |
| The characteristic number of protons per atom of an element. Used as an identifying attribute. |
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| Autotroph |
| An organism that synthesizes food molecules from inorganic molecules by using an external energy source, such as light energy. |
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| Auxins |
| Plant hormones responsible for stimulating growth. |
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