Glossary

Glossary of Some Common Environmental and Ecotoxicological Terms

A : B : C : D : E : F : G : H : L : M : O : P : R : S : T : U : V : W

Acid rain: precipitation (rain, snow, sleet etc) that is more acid than normal, generally due to human-produced air pollutants that dissolve in atmospheric moisture.

Acid sulfate soils:
soils containing highly acidic layers resulting from the oxidation of materials that are rich in iron sulfides. These soils can usually be identified by the presence of pale yellow mottles and coatings of jarosite.

Acute toxicity:
when a substance leads to harmful effects shortly (£ 96 hours) after one exposure at a relatively large dose. The exposure is normally sudden and often produces an emergency situation.

Aeration zone:
the zone above the water table where the voids in the soil or rock may contain water but are not fully saturated.

Alluvium:
unconsolidated deposit of earth (e.g. gravel, sand, mud) left by floodwaters in a river valley or delta.

Aquifer:
a relatively permeable rock layer below the water table that contains a significant amount of water. 

Asbestos:
a generic name for a group of naturally occurring mineral silicates that are characterised by fibres or bundles of fine single crystal fibrils. Included in the definition are the minerals chrysotile, crocidolite, amosite, anthophyllite, tremolite and actinolite.

Assessment:
Study of a site to determine possible and actual contaminants. May involve a desktop review of the site and also may include the collection and analysis of soil, groundwater or sediment samples.

Bedrock: solid rock underlying unconsolidated alluvium.

Benthos:
organisms associated with the bottom sediments of water bodies.

Bioaccumulation:
bioconcentration or biomagnification; the tendency for a substance to accumulate in living tissue. An organism may take in a substance, but not excrete or metabolise it; then, a predator eats the organism and ingests the substance already accumulated in the prey.

Bioremediation:
the use of bacteria and other small organisms (such as single-celled and multicellular microbes and fungi) to clean up or reduce the concentrations of environmental contaminants.

Biosolids:
the organic product that results from sewage treatment processes (alternatively known as sewage slugde) and food processing waste.

BTEX:
abbreviation for benzene, toluene, ethyl benzene, and xylenes. Commonly found group of petroleum hydrocarbon contaminants.

Carbamate pesticides: a group of synthetic organic pesticides that are less persistent than both organochlorine and organophosphate pesticides; includes carbaryl (sevin) and baygon.

Carcinogen:
a cancer-producing substance.

Catchment:
an area of land defined by ridges and hills in which all water flows to a common point.

Chronic toxicity:
the long-term, harmful effects arising from repeated exposure to relatively small amounts of a toxin over a prolonged time period.

Coliform bacteria:
bacteria, such as Escherichia coli, that live in the human intestine in huge numbers. The abundance of coliform bacteria in water is a good indicator of how much human feces has recently entered the water.

Contaminated:
In relation to land, underground waterunder that land of surface water on that land, means a substance present above background concentrations, that presents, or has the potential to present, a risk of harm to humans health, the environment or any environmental value.

Dioxins: a group of more than two hundred related compounds that are extremely toxic, by-products of certain industrial chemical processes and incomplete incineration of chlorinated hydrocarbon compounds. Also generated by bush fires, volcanoes and vehicle emissions.

Ecology: the study of how organisms (plants and animals) interact with each other and their environment.

Ecosystem:
a discrete physical unit that consists of living and non-living parts, interacting to form a system that supports on-going life.

Ecotoxic:
a substance that, if released into the environment, will cause or may cause immediate or delayed adverse impacts to the environment by means of bioaccumulation and/or toxic effects upon biotic systems.

Ecotoxicology:
the study of how chemicals affect entire ecosystems.

Electromagnetic radiation:
includes visible light, heat, ultraviolet radiation, gamma rays, X rays etc. The term radiation is also used to refer to the emission of particles (such as alpha and beta particles) from a radioactive atom.

Environment:
in the broadest sense, all aspects of the natural environment plus human manipulations and additions to the natural environment.

EnvironmentalToxicology
: See full explanation below

Erosion:
the deterioration and weathering of soil or rock.

Eutrophication:
a rapid increase in algae or plant growth in an aquatic system due to the influx of a limiting nutrient that was previously in short supply.

Evapotranspiration:
the transfer of water into the atmosphere by evaporation and transpiration (the release of water vapour by plants).

Fertiliser: a substance, often an artificial chemical mixture, that is spread on or through the soil to make it more fertile.

Fluvial:
of or found in rivers.

Fossil fuels:
coal, petroleum (oil, natural gas and asphalt) and related organic materials that have formed over geologic time.

Greenhouse effect: the warming up of the lower atmosphere due to the accumulation of greenhouse gases (carbon dioxide, methane, chlorofluorocarbons) that trap heat near the surface of the Earth.

Groundwater:
water that occurs below the Earth’s surface, contained in spaces between rocks, gravel and sand.

Habitat: the general place or physical environment in which a population lives.

Hazardous substance / waste:
substances / wastes that are particularly dangerous or destructive; specifically characterised by one or more of the following properties: flammable, corrosive, reactive or toxic.

Heavy metals:
generally defined as those elements occurring in the middle to bottom sections of the Periodic Table and exhibit densities that are high compared to those of other common materials. Includes cadmium, chromium, copper, lead, mercury, nickel and zinc. Various heavy metals are required in trace amounts by organisms (hence also the common term trace metals), but can cause damage when ingested in larger quantities, such as binding with enzymes and thus impairing their functions.

Herbicide:
a chemical substance used to kill plants.

Landfill: a site (hole in the ground) used for the purpose of disposing waste to land. In a modern sanitary landfill, the hole is lined so that materials will not escape and it is covered with layers of soil as it is progressively filled. When completely filled, it is capped and sealed with more soil and topsoil.

LD50:
the dose of a given substance that will kill 50% of a certain population. The Lethal Dose-50 has become the standard reference for summarising the toxicity of substances.

Leachate:
the liquid solution released by, or percolated through, porous waste material (such as refuse in a landfill or mining tailings) and containing dissolved and/or suspended chemical constituents, some of which may be hazardous.

Melanoma: a condition of malignant skin cancer.

Mutagen:
a substance that causes genetic mutations in sperm or egg cells.

Mutation:
a change in a gene, ultimately caused by a change in the DNA sequence.

Organochlorines: a diverse group of chemicals that always contain carbon and chlorine. Includes PVC, dioxins, PCBs and OCPs.

Organophosphate pesticides:
a group of synthetic organic pesticides that are less persistent than organochlorine pesticides; includes malathion, diazinon and parathion.

Ozone:
an O3 molecule, which contributes to air pollution in the troposphere, but is an important natural component of the stratospheric ozone layer (most concentrated at 20-25km altitude). The stratospheric ozone layer protects the Earth’s surface from excessive levels of ultraviolet radiation.

PAHs: a group of benzene-based hydrocarbons, including some highly hazardous compounds such as benzo(a)pyrene.

Pesticide:
any chemical manufactured to kill any organisms that humans consider undesirable.

pH scale:
a scale that is used to measure acidity; 1 is very acidic, 7 is neutral, and 14 is very basic (alkaline).

Phthalates:
hazardous synthetic chemicals used to soften plastics during manufacture.

Phytoremediation:
See full explanation below

Radioactivity: the emission of particles (such as alpha and beta particles) and rays (energy, such as gamma rays) from an unstable atom (radionuclide) as it disintegrates.

Receiving environment:
the place to where contaminants are transported and become mobilised pollutants.

Remediation:
efforts to counteract some, or all, of the effects of a contaminant after it has been released into the environment.

Restoration ecology:
activities designed to clean up air, soil and water and allow degraded or polluted ecosystems to be rehabilitated and revitalised.

Risk:
the probability (likelihood) that a substance / activity will produce harm under specific conditions; generally refers to any potential danger.

Saturation zone: the region below the water table where all voids in the soil and rock are fully filled with water.

Scum:
the floatable materials that form an accumulating layer on the liquid surface inside a primary waste water treatment tank; includes oils, grease and soaps.

Sediment:
material derived from weathered rocks, or biological or chemical processes, and deposited via water transport at or near the earth surface.

Site:
an area of land, underground water under the land, or surface water on that land.

Sludge:
materials that have settled to the bottom of a waste treatment device.

Soil:
a mixture of weathered rocks and minerals, decayed organic matter, living organisms, air and water.

Soil fertility:
the ability of the soil to support plant life and associated fauna. 

Sustainable development:
development that focuses on making social, economic and political progress to satisfy global human needs, desires, aspirations and potential without damaging the environment; also known as sustainable growth. 

Teratogen: a substance that adversely affects fetal development, such as when a pregnant woman ingests harmful chemicals.

Toxicity characteristics leaching procedure (TCLP):
a laboratory test which estimates the potential for a given chemical to leach from a non-liquid waste when it is deposited within a landfill. The test results indicate the environmental acceptability of disposing the non-liquid waste to landfill, with respect to that chemical.

Toxicology:
the study of the effects of chemicals that are harmful or fatal when exposed to organisms.

Understorey plants: trees and shrubs that grow close to the forest floor in the lower canopy.

Virgin excavated natural material: includes clay, gravel, sand, soil and rock that is not mixed with any other waste and has been excavated from areas that are not contaminated with manufactured chemicals and does not contain sulfidic ores or soils.

Water table: the sub-surface boundary between the zones of aeration and saturation.