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In ecology and geochemistry, attenuation is the ability to withhold contaminants in soil and groundwater by various mechanisms such as adsorption, dilution, dispersion or biological degradation (biodegradation, bioremediation), causing a decrease in concentration and toxicity compared to the total amount of the contaminant. In environmental engineering and remediation this is often called "natural attenuation".
Background level
An estimate of the natural concentration of a substance that would exist in the absence of any anthropogenic input, usually on a regional, sub-regional or catchment basis. For chemical elements in soils, the background concentration is expected to show some broad-scale variation depending on the nature of the geochemical parent materials.
A general term for the process by which an organism stores a higher concentration of a substance within its body than is found in its environment.
The amount of the contaminant that is available for absorption through the gastrointestinal tract (or lung surface), and is subsequently absorbed into the blood stream. The first process alone is also called bioaccessibility.
The removal or treatment of soil contaminated with chemicals at unacceptable concentrations.
This includes "any substance (including gases, odorous compounds, liquids, solids, and micro-organisms) or energy (excluding noise) or heat, that either by itself or in combination with the same, similar, or other substances, energy, or heat: (a) when discharged into water, changes or is likely to change, the physical, chemical, or biological condition of water; or (b) when discharged onto or into land or into air, changes or is likely to change the physical, chemical or biological condition of the land or air onto or into which it is discharged". (RMA definition, see Appendix 3.)
Contaminated land
Land of one of the following kinds: "(a) if there is an applicable national environmental standard on contaminants in soil, the land is more contaminated than the standard allows; or (b) if there is no applicable national environmental standard on contaminants in soil, the land has a hazardous substance in or on it that (i) has significant adverse effects on the environment; or (ii) is reasonably likely to have significant adverse effects on the environment". (RMA definition, see Appendix 3.)
A condition or state which represents or potentially represents an adverse health or environmental impact because of the presence of hazardous substances.
Dip bath or vat
A structure for immersing or wetting cattle or sheep to control ectoparasites with agrichemicals. This is usually an in-ground "bath" ranging from full immersion plunge-type pot dips through to straight or U-form swim-through dips, but is sometimes a shower booth or other above-ground facility. It is typically accompanied by a draining pen.
Draining pen
An area or platform located near the exit of the dip where sheep are directed right after they are dipped to drain off the liquid in their wool. Modern draining pens are sloped to take the dip back to the bath.
An area of nature, including living organisms and non-living substances, interacting to produce an exchange of material between the living and non-living parts. The term ecosystem implies interdependence between the organisms comprising the system.
Contact with a chemical, physical or biological agent.
Exposure assessment
The estimation of the magnitude, frequency, duration, route and extent of exposure to chemical substances or a contaminant.
The capacity to produce any adverse health or environmental effect.
Hot spots
Areas that contain very high levels of persistent chemicals, such as chemical mixing or storage areas, or pre-1980 sheep-dip sites.
Persistent chemicals
Chemicals that were used in agriculture and horticulture for their toxic properties and from which residues may remain in the soil for some time. For the purposes of this guideline the persistent chemicals are arsenic, DDT, dieldrin and lindane, which were used prior to 1980.
The use of plant species (eg, willows, poplars) to remediate soil contamination.
Pica condition
The word pica comes from the Latin word for magpie, a bird known for its large and indiscriminate appetite. As many as 25 percent to 30 percent of children (and 20 percent of patients in mental health clinics) have an eating disorder called pica, which is characterised by persistent and compulsive cravings to eat non-food items. A discussion document on pica can be accessed from:
An organism, plant, human or physical structure that may be exposed to a chemical or other hazardous agent.
The clean-up or mitigation of risks from contaminants in soil.
The probability and consequence of an adverse outcome in a person, a species, a group or an ecosystem that is exposed to a hazardous agent. Risk depends on the level of toxicity of the hazardous agent, as well as the level and length of exposure.
Risk assessment
a. Environmental risk assessment: the estimation of the probability and potential impact of chemicals or physical agents on a specified receptor or ecological system under a specific set of conditions.
b. Health risk assessment: the estimation of the probability and potential impact of a chemical or physical agent on a human receptor or a specified human population under a specific set of conditions.
The process involves reviewing existing information, identifying contaminant sources, potential exposure routes and receptors, and conducting soil sampling and analysis.
Scooping mound
The ground next to the dip bath, where the sludge from the old dip was bucketed or shovelled out of the sumps to clean, empty or renew the dip.
Sheep-dip site
The actual location of the dip bath or structure; in a wider sense it also includes the immediate dip surrounding and associated areas, such as the splash area, the scooping mound or the draining pen.
Soil guideline values
Levels of contaminants that are not considered to pose an unacceptable risk to human health or to the environment. They are also referred to as "soil acceptance criteria" in existing New Zealand guidelines.
Splash zone
The area where dip solution was spread in the process of sheep dipping (eg, where the sheep jumped into the dip bath).
Tolerable daily intake.
The dose or exposure below which a significant adverse effect is not expected.
The quality or degree of being poisonous or harmful to plant, animal or human life.