Glossary

Terms

Decommissioning

Decommissioning

Definition

The final stage of a development, involving the ceasing of operations, and the dismantling, removal and disposal of its component parts.

Delineation

Delineation

Definition

To draw or trace the outline/contour of a matter: e.g. in a DNAPL delineation study, investigation outcomes try to depict and draw where DNAPL is located.

Dense non-aqueous phase liquid (DNAPL)

Dense non-aqueous phase liquid (DNAPL)

Definition

DNAPLs are denser-than-water liquids, such as CHCs, that may exist in the ground as discrete or interconnected droplets or shallow pools on low-permeability layers. These substances are not very soluble in groundwater, so may exist for a long time, slowly dissolving and contaminating passing groundwater.

Related Terms

See also: Chlorinated hydrocarbon (CHC), Groundwater

Deposition

Deposition

Definition

The build-up, over time, of particulate material in the air or a liquid as it settles out of the air or that liquid.

Desorption

Desorption

Definition

A process in which a substance is released from or through a solid surface into another medium such as groundwater or air (opposite of sorption).

Diffusion

Diffusion

Definition

The movement of a substance through a solid, liquid or gas from a region of high concentration to a region of low concentration.

Dioxins

Dioxins

Definition

Dioxins and furans are halogenated aromatic hydrocarbons (compounds with carbons and hydrogen bound in a ring-format that has chlorine atoms attached to it). There are 75 different dioxins and 135 different furans. They are persistent organic pollutants, which can bioaccumulate in the body, potentially leading to cancer.

Related Terms

See also: Persistent organic pollutant (POP)

Directly-heated thermal desorption (DTD)

Directly-heated thermal desorption (DTD)

Definition

The technology used for the remediation of the CPWE. Contaminated soil is heated to high temperatures to volatilise and drive off the contaminants. The treated soil is cooled. The off gases are destroyed in a thermal oxidiser.

Related Terms

See also: CPWE, Off-gas

Dissolution

Dissolution

Definition

A process where a solid or separate-phase liquid substance is dissolved into a solvent to create a solution (e.g., like sugar or honey into a cup of tea).

Dissolved phase mass

Dissolved phase mass

Definition

A mass that is in a dissolved state in a liquid.

DNAPL

See: Dense non-aqueous phase liquid (DNAPL)

DNAPL source area

DNAPL source area

Definition

Area where residual or free phase DNAPL is present.

Related Terms

See also: Dense non-aqueous phase liquid (DNAPL)

Drawdown

Drawdown

Definition

A lowering of the water table of an unconfined aquifer or the potentiometric surface of a confined aquifer caused by pumping from wells.

Related Terms

See also: Aquifer