Contaminated and Hazardous Waste Site Management

Glossary E

Effective Porosity: The amount of interconnected pore space through which fluids can pass. Effective porosity is usually less than total porosity because some dead-end pores may be occupied by static fluid.

Effluent: Wastewater, treated or not treated, that flows out of a treatment plant, sewer or industrial pipe called an outfall. This term generally refers to wastes discharged into surface waters.

Electric Field: A vector field describing the force on a unit electrical charge [newtons/coulomb = volts/metre].

Electron Acceptor: A chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process. See also Terminal Electron Acceptor and Oxidation-Reduction.

Electron Donor: A chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process. See also electron acceptor and oxidation-reduction.

Elastic Moduli (elastic constants): Elastic moduli specify the stress- strain properties of isotropic materials in which stress is proportional to strain. They include bulk and shear moduli.

Electrical Logs: Provide information on porosity, hydraulic conductivity, and fluid content of formations drilled in fluid-filled boreholes. This record is based on the dielectric properties (e.g., electrical resistivity) of the aquifer materials measured by geophysical devices lowered down boreholes or wells.

Electrode: A piece of metallic material which acts as an electric contact with a non-metal. In chemistry, it refers to an instrument designed to measure an electrical response which is proportional to the condition being assessed (e.g. pH, resistivity).

Electromagnetic Method: A method which measures magnetic and/or electric fields associated with subsurface currents.

Emission: Pollution discharged into the atmosphere from smokestacks, other vents and surface areas of commercial or industrial facilities.

Empirical: Relying upon or gained from experiment or observation.

Enforcement: The EPA, State or local legal actions taken against parties to facilitate settlements; to compel compliance with laws, rules, regulations, or agreements; and/or to obtain penalties or criminal sanctions for violations. Enforcement procedures may vary, depending on the specific requirements of different environmental laws and related regulatory requirements. Under CERCLA, for example, the EPA will seek to require PRPs to clean up a Superfund site or pay for the cleanup (see Cost Recovery).

Entrained: Particulates or vapor transported along with flowing gas or liquid.

Enzyme: Any of numerous proteins or conjugated proteins produced by living organisms and

Equilibrium: Condition that exists in a system when the system does not undergo any change of properties with the passage of time; usually multiple forces produce a steady balance, resulting in no change over time.

Equipotential Map: A plot in which points of equal hydraulic head are connected.

Esker: A narrow long ridge like form comprised mainly of gravel and sand. These stratified glacio-fluvial deposits were formed in a stream bed flowing inside the ice of a glacier generally at the glacier bottom. The glacio- fluvial deposits were then left in place after the ice melted.

Eucaryotes: An organism having one or more cells with well-defined nuclei.

Evaporation: The process by which a liquid enters the vapor (gas) phase.

Evapotranspiration: Discharge of water from the earth's surface to the atmosphere by evaporation from water bodies and soil surfaces and by transpiration from plants.

Ex situ: Moved from its original place; excavated; removed or recovered from the subsurface.

Exposure: See Injection.

Extractable: A compound that can be partitioned into an organic solvent from the sample matrix and is amenable to gas chromatography. Extractables include semivolatile (BNA) and pesticide/Arochlor compounds.

Extractant, Extraction: A liquid solvent used to remove a solute from another liquid.

Extraction Well: A well employed to extract fluids (either water, gas, free product, or a combination of these) from the subsurface. Extraction is usually accomplished by either a pump located within the well or suction created by a vacuum pump at the ground surface.