Glossary

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Term Term description
data

Information, especially when it is to be analyzed or used as the basis for a decision.

DDT

A powerful insecticide that is also poisonous to humans and animals. It remains active in the environment for many years and has been banned in the United States for most uses since 1972. Short for dichlorodiphenyltrichloroethane C14H9Cl5.

dead zone

An area in a body of water, especially a river mouth emptying into an ocean, having oxygen levels that are not adequate to support aerobic life. Anoxic conditions are produced when excessive nutrients, usually from agriculture and human waste, are carried by the river to the ocean where algae growth is greatly stimulated. When these large blooms of algae die and sink to the bottom, the dead mass is quickly decomposed by bacteria which depletes the area of dissolved oxygen and kills the shellfish, invertebrates and fish.

deciduous

Trees and shrubs that shed their leaves at the end of the growing season.

decomposer

An organism, often a bacterium, fungus, or arthropod, that feeds on and breaks down dead plant or animal matter in the process of decomposition. Decomposers make essential nutrients available to plants and other organisms in the ecosystem.

decomposition

The process by which organic substances (dead plant and animal carcasses, or waste material) are broken down into simpler forms of matter. Decomposition is facilitated by decomposers like bacteria, fungi and many invertebrates.

deforestation

The cutting down and removal of all or most of the trees in a forested area. Deforestation can erode soils, contribute to desertification and the pollution of waterways, and decrease biodiversity through the destruction of habitat.

denitrification

A bacterially-mediated process that converts nitrate (NO3) in the soil into gaseous forms of nitrogen (NOx ,N2).

denitrifier

Bacteria that perform denitrification. There are a number of taxa included in this group, notably Alcaligenes faecalis, A. xylosoxidans, Bradyrhizobium japonicum, Blastobacter denitrificans, and many in the Pseudomonas genus.

deposition

The geological process in which sediments, soil and rocks are added to a landform or land mass. Wind, ice, and water transport previously eroded sediment, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.

desalination

The process of removing dissolved salts and minerals from seawater or brackish water. This process is energy intensive and often cost-prohibitive, but due to increasing demand for fresh water desalination operations are likely to increase in the future.

desertification

The transformation of land into desert. Desertification can result from climate change or from human practices such as deforestation and overgrazing.

diameter

A straight line from one side of something (such as a circle) to the other side that passes through the center point.

diatomic

A molecule made up of two atoms, either of the same or different chemical elements. For example, N2, O2, and OH+ are diatomic molecules.

diatoms

Diatoms are microscopic single-celled algae that are large contributors to the phytoplankton of oceans, seas and lakes. Together they are the single largest contributor of oxygen to the Earth's atmosphere, and form an important base to aquatic food webs. Diatoms have evolved to have elaborate silica cell walls that reflect the types of habitat to which the particular species is adapted. Diatoms are abundant in nearly every habitat where water is found – oceans, lakes, streams, mosses, soils, even the bark of trees. Diatoms grow as single cells, or form simple filaments or colonies.

diazinon

An insecticide that belongs to a group of chemicals known as organophosphates. Diazinon is used in agriculture to control insects on fruit, vegetable, nut and field crops.

differentiation

A process in which a mixture of materials separates out partially or completely into its constituent parts, as in the cooling and solidification of a magma into two or more different rock types or in the gradual separation of an originally homogeneous Earth into crust, mantle, and core.

dike

An embankment for controlling or holding back the waters of the sea or a river.

Dinitrogen gas

A colorless, odorless, gaseous element (N2)that constitutes about four-fifths of the volume of the atmosphere.

dinitrogen gas

A colorless, odorless, gaseous element (N2) that constitutes about four-fifths of the volume of the atmosphere.

dirt clod

A lump or chunk, especially of earth or clay.

discharge

The outflow of water from one area to another, such as groundwater forced up through soil emerging as an above-ground spring, or effluent from a waste-water treatment plant entering a stream or river.

distillation

The extraction of the volatile components of a mixture by the condensation and collection of the vapors that are produced as the mixture is heated.

distributive justice

A form of justice concerned with the equitable apportionment of privileges, duties, and goods based on both the merits of individuals and the satisfaction of basic human needs in a society.

 

domestic water use

Water used for indoor and outdoor household purposes: drinking, preparing food, bathing, washing clothes and dishes, brushing your teeth, watering the yard and garden and even washing the dog.

domestication

The process of hereditary reorganization of wild animals and plants into domestic and cultivated forms according to the interests of people. In its strictest sense, it refers to the initial stage of human mastery of wild animals and plants.

drainage basin

An area of land where all precipitation that falls will drain or flow downhill into a specific stream; a watershed.

drip line irrigation

A form of irrigation that saves water and fertilizer by allowing water to drip slowly to the roots of many different plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters. It is done through narrow tubes that deliver water directly to the base of the plant.

drought

Deficient precipitation or water runoff extending over an indefinite number of days, leading to extended dryness, crop failure, soil damage, and wildfire vulnerability.

Dust Bowl

The name given to 150,000-square-mile area, encompassing the Oklahoma and Texas panhandles and neighboring sections of Kansas, Colorado, and New Mexico, devastated by drought in 1930s depression-ridden America. the soil lacked the stronger root system of grass as an anchor, so the winds easily picked up the loose topsoil and swirled it into dense dust clouds, called “black blizzards.” Recurrent dust storms wreaked havoc, choking cattle and pasture lands and driving 60 percent of the population from the region.

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