A complex chemical and atmospheric phenomenon that occurs when emissions of sulfur and nitrogen compounds and other substances are transformed by chemical processes in the atmosphere, often far from the original sources, and then deposited on earth in either wet or dry form. The wet forms, popularly called "acid rain," can fall to earth as rain, snow, or fog. The dry forms are acidic gases or particulates. 

Drainage of water from areas that have been mined for coal or other mineral ores. The water has a low pH because of its contact with sulfur-bearing material and is harmful to aquatic organisms. 

Changes in an organism's physiological structure or function or habits that allow it to survive in new surroundings.

Land used for crops, pasture, and livestock; the adjacent uncultivated land that supports other vegetation and wildlife; and the associated atmosphere, the underlying soils, groundwater, and drainage networks.

Sudden spurts of algal growth, which can affect water quality adversely and indicate potentially hazardous changes in local water chemistry.

The conditions of the surrounding environment, most often used to mean the encompassing atmosphere ( e.g.,  air temperature, pressure), water, or soil.

Any unconfined portion of the atmosphere: open air, surrounding air, background air. 

An underground geological formation, or group of formations, containing water. Are sources of groundwater for wells and springs.

Organisms relating to, or occurring at, the bottom of a body of fresh or marine water.

The increase in concentration of contaminants in living organisms as they take in air, water, or food because the substances are very slowly metabolized or excreted 

Harvesting all the trees in one area at one time, a practice that can encourage fast rainfall or snowmelt runoff, erosion, sedimentation of streams and lakes, and flooding, and destroys vital habitat. 

used to refer to all forms of climatic inconsistency, but because the Earth's climate is never static, the term is more properly used to imply a significant change from one climatic condition to another. In some cases, 'climate change' has been used synonymously with the term, 'global warming'; scientists however, tend to use the term in the wider sense to also include natural changes in climate. 

A measure of the volume of a substance flowing through space within a fixed period of time. (in this case, one second)

The first chlorinated hydrocarbon insecticide chemical name: Dichloro-Diphenyl-Trichloroethane). It has a half-life of 15 years and can collect in fatty tissues of certain animals. EPA banned registration and interstate sale of DDT for virtually all but emergency uses in the United States in 1972 because of its persistence in the environment and accumulation in the food chain. 

The lowest concentration of a chemical that can reliably be distinguished from a zero concentration.

The oxygen freely available in water, vital to fish and other aquatic life and for the prevention of odors. DO levels are considered a most important indicator of a water body's ability to support desirable aquatic life. Secondary and advanced waste treatment are generally designed to ensure adequate DO in waste-receiving waters.

The direction that groundwater flows; similar to "downstream" for surface water.