Glossary of terms

​​​​abiotic: the nonliving components of a system (refer to biota).

absorption: in chemistry, penetration of one substance into the body of another. In biology, the act of absorbing (to take in as fluids or gases through a cell membrane). To take a substance (e.g. water, nutrients) into the body through the skin or mucous membranes or, in plants, through root hairs.

acceptable contaminant concentration (ACC): the maximum concentration (mg/L) of contaminant in irrigation water that can be tolerated for a shorter period of time (20 years) assuming the same maximum annual irrigation loading as desirable contaminant concentration (DCC).

acclimation: short-term adaptation of individual organisms to specific environmental conditions.

acid-soluble metal: the concentration of the metal that passes through a 0.45 µm membrane filter after the sample is acidified to pH 1.5 to 2.0 with nitric acid.

acidic: having a high hydrogen ion concentration (low pH).

acid volatile sulfides (AVS): sulfides in sediments that liberate hydrogen sulfide on reaction with cold dilute acid (mainly FeS or MnS in sediments).

acute toxicity: a lethal or adverse sub-lethal effect that occurs as the result of a short exposure period to a chemical relative to the organism’s life span.

acute-to-chronic ratio (ACR): the species mean acute value (LC/EC50) divided by the chronic value (e.g. NOEC or EC10) for the same species.

additive toxicity: the toxicity of a mixture of chemicals that is approximately equivalent to that expected from a simple summation of the known toxicities of the individual chemicals present in the mixture (algebraic summation of effects).

adsorption: the taking up of one substance at the surface of another.

aerobic: of organisms requiring oxygen for respiration or conditions where oxygen is available.

aesthetic: aspects of, say, a water body, that can be considered beautiful or pleasant to the senses.

‘aggressive’ carbon dioxide: the amount of dissolved carbon dioxide in excess of that required to stabilise the bicarbonate ion present in water.

algae: comparatively simple chlorophyll-bearing plants, most of which are aquatic and microscopic in size.

alkalinity: the quantitative capacity of aqueous media to react with hydroxyl ions. The equivalent sum of the bases that are titratable with strong acid. Alkalinity is a capacity factor that represents the acid-neutralising capacity of an aqueous system.

alkaloids: nitrogenous organic bases found in plants.

allochthonous: organic material that is developed or derived outside a particular waterbody.

ambient water: all water generally of natural occurrence (e.g. lakes, rivers, wetlands, estuaries, oceans).

anaerobic: conditions where oxygen is lacking; organisms not requiring oxygen for respiration.

analytes: the physical and chemical species (indicators) to be determined.

anion: negatively charged ion.

anionic: characteristic behaviour or property of an ion that has a negative charge. Anions move to the anode in electrolysis.

antagonism: a phenomenon in which the effect or toxicity of a mixture of chemicals is less than that which would be expected from a simple summation of the effects or toxicities of the individual chemicals present in the mixture (algebraic subtraction of effects).

anthropogenic: produced or caused by humans.

a posteriori: identifying causes by inductive reasoning based on actual effects, consequences or facts (from observation, experience or experiment).

a priori: predicting effects by deductive reasoning based on causes rather than actual observation, experience or experiment.

aquaculture: commonly termed fish farming, but it broadly refers to the commercial growing of marine (mariculture) or freshwater animals and aquatic plants.

aquatic ecosystem: any watery environment from small to large, from pond to ocean, in which plants and animals interact with the chemical and physical features of the environment.

aquifer: an underground layer of permeable rock, sand or gravel that absorbs water and allows it free passage through pore spaces.

assessment factor (AF): a unitless number applied to the lowest toxicity figure for a chemical to derive a concentration that should not cause adverse environmental effects. The size of the AF varies with the type of data. Also called ‘application factor’ or ‘safety factor’.

assimilation: the incorporation of absorbed substances into cellular material.

assimilative capacity: the maximum loading rate of a particular pollutant that can be tolerated or processed by the receiving environment without causing significant degradation to the quality of the ecosystem and hence the community values it supports.

autochthonous: organic material that is developed or produced within a particular waterbody.

autotrophy: the nutrition of organisms that produce their own organic constituents from inorganic compounds, using energy from sunlight or oxidation processes (e.g. most plants and some bacteria).

BACI: Before–after, control–impact

baseline data (studies): collected (undertaken) before a development begins. Also called ‘pre-operational data’ (studies).

BEC10: the concentration in a toxicity test that is the highest tested concentration that has an upper 95% confidence interval that causes less than a 10% effect.

benthic: referring to organisms living in or on the sediments of aquatic habitats (e.g. lakes, rivers, ponds).

benthos: the sum total of organisms living in, or on, the sediments of aquatic habitats.

binding sites: sites on a substrate where chemical interaction with an indicator may occur. The interaction may be electrostatic, polar, hydrogen bonding or covalent bonding.

bioaccumulation: the process by which chemical substances are accumulated by aquatic organisms by all routes of exposures (dietary and the ambient environment).

bioaccumulation factor (BAF): the ratio of the concentration of a contaminant in an organism to its concentration in the ambient environment at a steady state, where the organism can take in the contaminant through ingestion with its food as well as through direct contact. It can be expressed on a wet weight, dry weight or lipid weight basis.

bioassay: a test that exposes living organisms to several levels of a substance that is under investigation, and evaluates the organisms’ responses.

bioavailable: able to be taken up by organisms.

biochemical (or biological) oxygen demand: the decrease in oxygen content in mg/L of a sample of water in the dark at a certain temperature over a certain of period of time which is brought about by the bacterial breakdown of organic matter. Usually the decomposition has proceeded so far after 20 days that no further change occurs. The oxygen demand is measured after 5 days (BOD5), at which time 70% of the final value has usually been reached.

bioconcentration: the process by which chemical substances are accumulated by aquatic organisms via absorption through the respiratory and dermal surfaces (dietary exposure is excluded).

bioconcentration factor (BCF): the ratio of the concentration of a contaminant in an organism to its concentration in the ambient water (or sediment) at a steady state. It can be expressed on a wet weight, dry weight or lipid weight basis.

biodiversity (biological diversity): the variety of life forms, including the plants, animals and microorganisms, the genes they contain and the ecosystems and ecological processes of which they are a part.

biofilm: layer of materials created by microorganisms on an underwater surface.

biological assessment: use and measurement of the biota to monitor and assess the ecological health of an ecosystem.

biological community: an assemblage of organisms characterised by a distinctive combination of species occupying a common environment and interacting with one another.

biomagnification: the process by which tissue concentrations of chemicals increase as the chemical passes up through two or more trophic levels in a food chain.

biomagnification factor (BMF): the ratio of contaminant concentration in an organism to that in its diet at steady state.

biosolids: sewage sludge, organic residuals remaining after domestic sewage treatment.

biota: the sum total of the living organisms of any designated area.

biotoxins: a toxin (a poison) which originates from a living thing (e.g. a plant, animal, fungi, bacteria).

bioturbation: the physical disturbance of sediments by burrowing and other activities of organisms

bounded effect concentration (BEC): the concentration in a toxicity test that is the highest tested concentration that has an upper 95% confidence interval that causes less than a specified percent effect.

buffer: a solution containing a weak acid and its conjugate weak base, the pH of which changes only slightly on the addition of acid or alkali.

buffering capacity: a measure of the relative sensitivity of a solution to pH changes on addition of acids or base.

catchment: the total area draining into a river, reservoir, or other body of water.

cation: positively charged ion.

cation exchange capacity (CEC): a measure of a soil’s ability to retain cations.

cationic: the characteristic behaviour or property of an ion with a positive charge. Cations move to the cathode in electrolysis.

chelate: the type of coordination compound in which a central metal ion is attached by co-ordinate links to two or more nonmetal atoms in the same molecule, called ligands.

chemical oxygen demand (COD): the amount of oxygen required to oxidise all organic matter that is susceptible to oxidation by a strong chemical oxidant.

chlorination: in chemistry, the process of introducing one or more chlorine atoms into a compound. In water management, the application of chlorine to water, sewage or industrial wastes for disinfection.

chronic toxicity: a lethal or sublethal adverse effect that occurs after exposure to a chemical for a period of time that is a substantial portion of the organism’s life span or an adverse effect on a sensitive early life stage.

colloid: material in solution typically 1 nm to 100 nm in diameter. Colloidal particles do not settle out of solution through the force of gravity. Organic colloidal matter is considered especially important in the transport of inorganic substances such as phosphorus through the soil profile.

community: an assemblage of organisms characterised by a distinctive combination of species occupying a common environment and interacting with one another.

community composition: all the types of taxa present in a community.

community metabolism: the biological movement of carbon in an ecosystem, involving two processes, production (via photosynthesis) and respiration.

community structure: all the types of taxa present in a community and their relative abundances.

community value: a particular value or use of the environment that is important for a healthy ecosystem or for public benefit, welfare, safety or health and that requires protection from the effects of stressors. Also known as ‘environmental values’, ‘beneficial uses’ or ‘national values’. Learn more about community values.

complexation: the formation of a compound by the union of a metal ion with a nonmetallic ion or molecule called a ligand or complexing agent.

compliance: action in accordance with upholding a ‘standard’ (water quality).

concentration: the quantifiable amount of a substance in water, biota, soil or sediment.

conceptual model: an abstraction (e.g. narrative, table, matrices of factor, pictorial, box-and-arrow diagram) that describes the components and processes that are deemed important in a system and the relationships between them. It documents assumptions about how components and processes are related and identifies gaps in knowledge. It is a working hypothesis about system form and function. Learn more about conceptual models.

contaminant: biological or chemical substances or entities, not normally present in a system, which may be capable of producing an adverse effect in a biological system, seriously injuring structure or function.

control: a series of test vessels in a toxicity test that are ideally exactly like the treated vessels except that they do not have the toxicant added.

cumulative: resulting from successive additions at different times or in different ways.

cumulative contaminant loading limit (CCL): is the maximum contaminant loading in soil defined in gravimetric units (kg/ha); it indicates the cumulative amount of contaminant added, above which site-specific risk assessment is recommended if irrigation and contaminant addition is continued.

cyanobacteria: a division of photosynthetic bacteria (formerly known as blue-green algae) that can produce strong toxins.

cyanosis: a blueness in the appearance of surficial tissues, generally due to a deficiency of oxygen bound to haemoglobin.

cytotoxic: having an adverse impact on cells.

decision criteria: criteria by which decisions will be made as a result of monitoring for potential impacts. Also refer to effect size, Type I error, Type II error.

default guideline value (DGV): a guideline value recommended for generic application in the absence of a more specific guideline value (e.g. a site-specific guideline value) in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Formerly known as ‘trigger values’.

depuration: process that uses a controlled aquatic environment to reduce the level of pathogenic organisms that may be present in live shellfish.

desirable contaminant concentration (DCC): the DCC is the maximum concentration (mg/L) of contaminant in irrigation water which can be tolerated assuming 100 years of irrigation based on stated irrigation loading assumptions.

detection limit: the minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero in water or sediment, using a specific analytical method.

detritus: unconsolidated sediments composed of both inorganic and dead and decaying organic material.

direct toxicity assessment (DTA): the use of toxicity tests to determine the acute and/or chronic toxicity of waste water discharges or total pollutant loads in receiving waters. (Assesses the toxicity of mixtures of chemicals rather than individual chemicals.)

diurnal: daily.

divalent: having a valence (combining power at atomic level) of two (e.g. calcium, Ca2+).

DO: dissolved oxygen

DOC: dissolved organic carbon

dose: the quantifiable amount of a material introduced into an animal.

early detection: measurable biological, physical or chemical response in relation to a particular stress, prior to significant adverse effects occurring on the system of interest.

early life-stage test: 28-day to 32-day exposures (60-day post-hatch for salmonids) of the early life stages of a species of fish from shortly after fertilisation through embryonic, larval and early juvenile development. Data are obtained on survival and growth.

ECse: the electrical conductivity of the soil saturation extract.

ECs: the electrical conductivity of the soil solution at maximum field water content.

EC1:5: the electrical conductivity of a 1:5 soil:water extract.

EC50 (median effective concentration): the concentration of a substance in water or sediment that is estimated to produce a 50% change in the response being measured or a certain effect in 50% of the test organisms relative to the control response, under specified conditions.

ecological integrity (health): the ‘health’ or ‘condition’ of an ecosystem. The ability of an ecosystem to support and maintain key ecological processes and organisms so that their species compositions, diversity and functional organisations are as comparable as possible to those occurring in natural habitats within a region.

ecologically sustainable development: development that improves the total quality of life, both now and in the future, in a way that maintains the ecological processes on which life depends.

ecosystem condition: the current or desired state of health of an ecosystem, relative to the degree of human disturbance.

ecosystem health: in the Water Quality Guidelines, this is synonymous with ‘ecological integrity’.

ecosystem receptor: any living organism or natural habitat that could be exposed to a stressor.

ecotoxicology: the science dealing with the adverse effects of chemicals, physical agents and natural products in the environment on populations, communities and ecosystems of living organisms.

ECx: the concentration of a substance in water or sediment that is estimated to produce an x% change in the response being measured or a certain effect in x% of the test organisms, under specified conditions.

effect size: the size of impact that would cause concern (or constitute an early warning). Often defined as a level of (ecological) change that is acceptable in comparison to a defined reference.

effluent: a complex waste material (e.g. liquid industrial discharge or sewage) that may be discharged into the environment.

electrical conductivity: the ability of water or soil solution to conduct an electric current.

encrustation: accumulation of material on surfaces through chemical or biological processes.

endemic, endemism: confined in occurrence to a local region.

endpoint: the specific response of an organism that is measured in a toxicity test (e.g. mortality, growth, a particular biomarker).

enterococci: any streptococcal bacteria normally found in the human intestinal tract; usually nonpathogenic.

epilimnion: the uppermost layer of water in a lake, characterised by an essentially uniform temperature that is generally warmer than elsewhere in the lake, and by relatively uniform mixing by wind and wave action.

epilithon: organisms attached to rocks, such as algae and lichens.

epiphyte: a plant that grows on the outside of another plant, using it for support only and not obtaining food from it.

eukaryotes: an organism characterised by the presence of membrane-bound organelles (refer to prokaryote).

euphotic: of surface waters to a depth of approximately 80 to 100 m; the lit region that extends virtually from the water surface to the level at which photosynthesis fails to occur because of reduced light penetration.

euryhaline: describes organisms that are capable of osmo-regulating over a wide range of salinities.

eutrophic: abundant in nutrients and having high rates of productivity frequently resulting in oxygen depletion below the surface layer of a waterbody.

eutrophication: enrichment of waters with nutrients, primarily phosphorus, causing abundant aquatic plant growth and often leading to seasonal deficiencies in dissolved oxygen.

evapotranspiration: the combined loss of water from a given area during a specified period of time by evaporation from the soil or water surface and by transpiration from plants.

exchangeable sodium percentage (ESP): the sodium adsorbed onto clay mineral surfaces as a proportion of the total cation exchange capacity of those surfaces.

exposure: the amount of physical or chemical agent that reaches a target or receptor.

fate: disposition of a material in various environmental compartments (e.g. soil or sediment, water, air, biota) as a result of transport, transformation and degradation.

field capacity: the greatest amount of water that it is possible for a soil to hold in its pore spaces after excess water has drained away.

flocculation: in chemistry, the process by which suspended colloidal or very fine particles coalesce and agglomerate into well-defined hydrated floccules of sufficient size to settle rapidly. Also, the stirring of water after coagulant chemicals have been added to promote the formation of particles that will settle.

fluorosis: chronic poisoning by fluorine.

fouling: accumulation of material through chemical, physical or biological processes.

free carbon dioxide: the amount of dissolved carbon dioxide in excess of that required to stabilise the bicarbonate ion present in water.

gilvin: the coloured component of dissolved organic matter in water, composed mainly of humic, fulvic and tannic compounds.

gross alpha (activity): a measure of the concentration of alpha-particle emitting radionuclides in water. This is determined by standard techniques involving the evaporation of a water sample and measurement of the alpha activity of the residue.

gross beta (activity): a measure of the concentration of beta-particle emitting radionuclides in water. This is determined by standard techniques involving the evaporation of a water sample and measurement of the beta activity of the residue.

groundwater: water stored underground in rock crevices and in the pores of geologic materials that make up the earth's crust; water that supplies springs and wells.

guidelines: a resource (document or website) that provides information and guidance on how to deal with a specific issue.

guideline value: a measurable quantity (e.g. concentration) or condition of an indicator for a specific community value below which (or above which, in the case of stressors such as pH, dissolved oxygen and many biodiversity responses) there is considered to be a low risk of unacceptable effects occurring to that community value. Guideline values for more than one indicator should be used simultaneously in a multiple lines of evidence approach. (Also refer to default guideline value and site-specific guideline value.)

habitat: the place where a population (e.g. human, animal, plant, microorganism) lives and its surroundings, both living and non-living.

half-life: time required to reduce by one-half the concentration of a material in a medium (e.g. soil or water) or organism (e.g. fish tissue) by transport, degradation, transformation or depuration.

hardness: The concentration of all metallic cations, except those of the alkali metals, present in water. In general, hardness is a measure of the concentration of calcium and magnesium ions in water and is frequently expressed as mg/L calcium carbonate equivalent.

hazard: the potential or capacity of a known or potential environmental contaminant to cause adverse ecological effects.

hazardous concentration (HC): the concentration of a substance that is predicted to potentially cause adverse effects to a specified percentage of species (e.g. HC05 is the concentration potentially hazardous to 5% of species).

hepatotoxin: toxic substances which adversely affect the liver.

heterotrophy: the nutrition of plants and animals that are dependent on organic matter for food.

humic substances: organic substances only partially broken down that occur in water mainly in a colloidal state. Humic acids are large-molecule organic acids that dissolve in water.

hydrogeology: study of subsurface waters and with related geologic aspects of surface water.

hydrograph: graphical representation of river or stream discharge or of water-level fluctuations in a well.

hydrolysis: in chemistry, the formation of an acid and a base from a salt by the ionic dissociation of water. Also, the decomposition of organic compounds by interaction with water.

hydrophilic: having an affinity for water, readily absorbs water.

hydrophobic: having little or no affinity for water, repels or does not absorb water.

hypolimnion: the region of a waterbody that extends from below the thermocline to the bottom of the lake; it is thus removed from much of the surface influence.

hypothesis: supposition made from known facts as a starting-point for further investigation.

hypoxia: deficiency of oxygen in tissues or in blood; anoxia.

IC50: the concentration of a substance in water or sediment that is estimated to produce a 50% inhibition of the response being measured in test organisms, relative to the control response, under specified conditions.

ICx: the concentration of a substance in water or sediment that is estimated to produce an x% inhibition of the response being measured in test organisms relative to the control response, under specified conditions.

index (indices): composite value(s) that can give a quick ranking to a waterbody or other ecosystem feature, derived via a formula that combines measurements of important ecosystem characteristics; typically used to rank ‘health’ or naturalness.

indicator: a parameter that can be used to provide a measure of a pressure, stressor and/or ecosystem condition response.

inorganic carbon: generally, simple ions and molecules that contain carbon bonded only to inorganic atoms. Carbonates are the most common group, although the cyanide ion is also considered to be inorganic.

interstitial: occurring in interstices or spaces; applied to water and to flora and fauna living between sand grains and soil particles.

invertebrates: animals lacking a dorsal column of vertebrae or a notochord.

in vitro: outside the intact organism; generally applied to experiments involving biochemical events occurring in tissue fragments or fractions in a laboratory.

ion: an electrically charged atom.

Langelier saturation index (SI): an index based on the tendency of water to deposit or dissolve calcium carbonate. It relates the actual pH of water with the pH at which water is saturated with calcium carbonate (SI = pH – pHS).

LC50 (median lethal concentration): the concentration of a substance in water or sediment that is estimated to be lethal to 50% of a group of test organisms, relative to the control response, under specified conditions.

LCx: the concentration of a substance in water or sediment that is estimated to be lethal to x% of a group of test organisms under specified conditions.

LD50: the dose of a substance received by a group of organism that is expected to be lethal to 50% of a group of test organisms under specified conditions.

leachate: water that has passed through a soil and that contains soluble material removed from that soil.

leaching: in the salinity and sodicity section of Chapter 4 in the ANZECC & ARMCANZ (2000) guidelines, refers to the downward movement of water and solutes below the root zone.

leaching fraction (LF): the proportion of water applied to the surface of a soil (e.g. as irrigation or rainfall) that drains below the root zone in the soil profile.

leading practice: the best possible way of conducting activities for a given site.

lentic: standing body of water such as a lake or pond.

lethal: causing death by direct action. Death of aquatic organisms is the cessation of all visible signs of biological activity.

level of protection (LoP): a degree of protection afforded to a water body based on its ecosystem condition. Learn more about level of protection.

life-cycle study: a chronic (or full chronic) study in which all the significant life stages of an organism are exposed to a test material. Generally, a life-cycle test involves an entire reproductive cycle of the organism. A partial life-cycle toxicity test includes the part of the life cycle observed to be especially sensitive to chemical exposure.

ligand: a molecule, ion or atom that is attached to the central atom of a coordination compound, a chelate or other complex. May also be called complexing agent.

line of evidence: information for an indicator or set of indicators used to monitor, assess or manage water or sediment quality.

liveweight: weight of the living animal.

local water quality issue: no need to define.

long-term trigger value (LTV): the maximum concentration of contaminant in irrigation water which can be tolerated assuming 100 years of irrigation, based on key irrigation loading assumptions.

lotic: flowing waters (e.g. rivers and streams).

lowest observed effect concentration (LOEC): the lowest concentration of a material used in a toxicity test that has a statistically significant adverse effect on the exposed population of test organisms as compared with the controls.

macrophyte: a member of the macroscopic plant life of an area, especially of a body of water; large aquatic plant.

management goal: a measure or statement used to assess whether community values are being attained or maintained. It should reflect the desired level of protection and provide precise and detailed descriptions of which aspects of the community values are to be protected. Learn more about management goals.

management strategy: documentation of actions and approaches to achieve the water quality objectives and management goals and, hence, protect the community values.

maximum acceptable toxicant concentration (MATC): the geometric mean of the lowest exposure concentration that causes a statistically significant adverse effect (LOEC) and the highest exposure concentration where no statistically significant effect is observed (NOEC).

maximum tolerable daily level (MTDL): the dietary level that when fed for a limited period, will not impair animal performance and should not produce unsafe residues in produce for human consumption.

MBACI: multiple before–after, control–impact

MBACIP: multiple before–after, control–impact, paired

median: middle value in a sequence of numbers.

mesotrophic: water bodies or organisms which are intermediate between nutrient-rich and nutrient-poor.

metabolite: any product of metabolism.

methylation: the introduction of methyl (CH3) groups into organic and inorganic compounds.

mixing zones: an explicitly defined area around an effluent discharge where effluent concentrations may exceed guideline values and therefore result in certain community values not being protected. The size of the mixing zone is site specific. Learn more about mixing zones.

monomeric: a chemical compound comprising single molecules.

morphometry: the form, shape and dimensions of an entity (e.g. waterbody or animal).

multiple lines of evidence: two or more lines of evidence that can be combined to monitor, assess or manage water or sediment quality.

Munsell scale: a means of expressing the colour of a soil by matching it against a colour chart.

necrotic: localised dying tissue.

neurotoxin: toxic substances which adversely affect the nervous system.

no observed effect concentration (NOEC): the highest concentration of a material used in a toxicity test that has no statistically significant adverse effect on the exposed population of test organisms as compared with the controls.

not detectable: below the limit of detection of a specified method of analysis.

octanol:water partition coefficient (POW): the ratio of a chemical's solubilities in n-octanol and water at equilibrium. The logarithm of POW is used as an indication of a chemical's propensity for bioconcentration by aquatic organisms.

off-flavour: result of the accumulation of certain pollutants such as petroleum hydrocarbons in fish or shellfish to a level that affects the flavour, making the product undesirable for human consumption; also known as tainting.

oligotrophic: waters with a small supply of nutrients.

organic carbon: generally carbon which is chemically bonded to other carbon atoms, although methane (one carbon atom only) and its derivatives are considered organic.

organism: any living animal or plant; anything capable of carrying on life processes.

osmoregulation: the biological process of maintaining the proper salt concentration in body tissues to support life.

osmosis: diffusion of a solvent through a semi-permeable membrane into a more concentrated solution, tending to equalise the concentrations on both sides of the membrane.

oxidation: the combination of oxygen with a substance, or the removal of hydrogen from it or, more generally, any reaction in which an atom loses electrons.

oxygenation: the process of adding dissolved oxygen to a solution.

PAH: polycyclic aromatic hydrocarbon.

parameter: a measurable or quantifiable characteristic.

partition coefficient: a ratio of the equilibrium concentration of the chemical between a non-polar and polar solvent.

pathogen: an organism capable of eliciting disease symptoms in another organism.

pelagic: term applied to organisms of the plankton and nekton which inhabit the open water of a sea or lake.

percentile: division of a frequency distribution into one hundredths.

periphyton: the organisms attached to submerged plants.

pH: value that represents the acidity or alkalinity of an aqueous solution. It is defined as the negative logarithm of the hydrogen ion concentration of the solution.

pH (CaCl2): measurement of soil pH in a 1:2.5 solution of soil:0.01M CaCl2. The CaCl2 solution is used because it has an ionic strength similar to that of soil water.

photodegradation: breakdown of a substance by exposure to light; the process whereby ultra-violet radiation in sunlight attacks a chemical bond or link in a chemical structure.

photolysis: the decomposition of a compound into simpler units as a result of the absorption of one or more quanta of radiation.

photosynthesis: the conversion of carbon dioxide to carbohydrates in the presence of chlorophyll using light energy.

physical and chemical stressor (PC stressor): naturally-occurring physical and chemical stressors, excluding toxicants, can cause serious degradation of aquatic ecosystems when ambient values are too high and/or too low.

physico-chemistry: refers to the physical and chemical characteristics of water. Covered under this term is physical and chemical stressors, toxicants and sediment.

phytoplankton: small (often microscopic) aquatic plants suspended in water.

phytotoxicity: toxicity of contaminants to plants.

pilot program: a field investigation similar in design to a sampling program, but less ambitious in scope. It is used to assess preliminary indicator values, spatial and temporal variability and logistic issues before definitive sampling.

plankton: plants (phytoplankton) and animals (zooplankton), usually microscopic, floating in aquatic systems.

pollution: the introduction of unwanted components into waters, air or soil, usually as result of human activity; e.g. hot water in rivers, sewage in the sea, oil on land.

polychlorinated biphenyls: highly toxic and persistent compounds derived from the replacement by Cl radicals of numerous H radicals on biphenyl, which consists of two benzene rings joined by a covalent bond, with the elimination of two H radicals (C12H10).

potable water: water suitable, on the basis of both health and aesthetic considerations, for drinking or culinary purposes.

practical quantitation limit (PQL): is the lowest level achievable among laboratories within specified limits during routine laboratory operations. The PQL is often around 5 times the method detection limit.

precipitation: in chemistry, the formation of solid particles in a solution; generally, the settling out of small particles. Also, the settling-out of water from cloud, in the form of rain, hail, snow, etc.

pressure: any human activity or biophysical change that has the potential to have an impact on the natural environment.

primary production: the production of organic matter from inorganic materials.

producers: organisms that are able to build up their body substance from inorganic materials.

prokaryotes: organisms characterised by the absence of membrane-bound organelles (opposite to eukaryotes).

protective concentration: the concentration of a substance that is predicted to protect a specified percentage of species from adverse effects (e.g. PC95 is the concentration protective of 95% of species and is equivalent to the HC5).

protocol: a formally agreed method and procedure for measuring an indicator; it defines the sampling, sample handling procedures and sample analysis.

protozoans: single-celled, animal-like organisms of the kingdom Protista.

pseudoreplication: replication in which the samples are not independent but instead are from sub-populations of a population: replicates that are actually subsamples of one sample are pseudoreplicates; and samples from various sites along a stretch of river are pseudoreplicates because the water is the same, moving between sites.

quality assurance (QA): the implementation of checks on the success of quality control (e.g. replicate samples, analysis of samples of known concentration).

quality control (QC): the implementation of procedures to maximise the integrity of monitoring data (e.g. cleaning procedures, contamination avoidance, sample preservation methods).

radiological: pertaining to nuclear radiation.

rapid biological assessment: a form of biological assessment, best developed using stream macroinvertebrate communities, that uses standardised, cost-effective protocols to provide rapid sample processing, data analysis, reporting and management response. The results from such assessments are likely to be reliable to detect large impacts but not small or minor impacts.

recruitment: in the Water Quality Guidelines, the replenishment or addition of individuals of an animal or plant population through reproduction, dispersion and migration.

redox potential: an expression of the oxidising or reducing power of a solution relative to a reference potential. This potential is dependent on the nature of the substances dissolved in the water, as well as on the proportion of their oxidised and reduced components.

reference condition: an environmental quality or condition that is defined from as many similar systems as possible and used as a benchmark for determining the environmental quality or condition to be achieved and/or maintained in a particular system of equivalent type.

risk: a statistical concept defined as the expected likelihood or probability of undesirable effects resulting from a specified exposure to known or potential environmental concentrations of a material. A material is considered safe if the risks associated with its exposure are judged to be acceptable. Estimates of risk may be expressed in absolute or relative terms. Absolute risk is the excess risk due to exposure. Relative risk is the ratio of the risk in the exposed population to the risk in the unexposed population.

Ryznar (stability) index: index relating the pH of water (pH) to the pH of water just saturated with calcium carbonate (pHs).

salinity: the presence of soluble salts in or on soils or in water.

sediment: unconsolidated mineral and organic particulate material that settles to the bottom of aquatic environment.

sediment pore waters: water that occupies the space between particles in a sediment, as distinct from overlying water which is the water above the sediment layer.

sediment quality: the physical, chemical and biological characteristics of sediment and the measure of its condition relative to the requirements for one or more biotic species and/or to any human need or purpose.

sediment quality objective: the guideline value and/or narrative statement for each selected indicator for sediment quality that should ensure the protection of all identified community values. Learn more about sediment quality objectives.

short-term trigger value (STV): the maximum concentration of contaminant in irrigation water which can be tolerated for a shorter period of time (20 years) assuming the same maximum annual irrigation loading to soil as for the long-term trigger value.

simultaneously extracted metals: the sum of the molar concentrations of heavy metals (excluding iron and manganese) that are solubilised with cold dilute acid; usually measured simultaneously with the measurement of acid volatile sulfides (AVS).

site-specific guideline value: a guideline value that is relevant to the specific location or conditions that are the focus of a given assessment or issue.

sodicity: the presence of a high proportion of sodium ions relative to other cations in a soil.

sodium adsorption ratio (SAR): the concentration of sodium relative to calcium and magnesium in the soil solution.

solution concentration: concentration of solutes in the soil water phase. The solutes, which may be contaminants, in the soil water are generally regarded as being highly available to organisms.

sorption: process whereby contaminants in soils adhere to the inorganic and organic soil particles.

speciation: the intimate chemical environment of the indicator, that is the compound or ion of which it forms a part.

species (biological): a group of organisms that resemble each other to a greater degree than members of other groups and that form a reproductively isolated group that will not produce viable offspring if bred with members of another group.

species (chemical): most commonly used for metals, chemical species are different forms of a particular chemical that may include different oxidation states, isotopes, complexes with organic ligands (in the case of metals) or with particulate matter.

species richness: the number of species present (generally applied to a sample or community).

suspended particulate matter (SPM): this is insoluble material which resides in the water column, or is dispersed in a sample upon agitation.

stakeholder: a person or group (e.g. an industry, a government jurisdiction, a community group, the public) who have an interest or concern in something. Learn more about stakeholder involvement.

standard (water quality): an objective that is recognised in enforceable environmental control laws of a level of government.

standing crop: the weight of organic material that can be sampled or harvested by normal methods at any one time from a given area.

static system: an exposure system of aquatic toxicity tests in which the test chambers contain solutions of the test material or control water that are not usually changed during the test. Depending on conditions, a static system may or may not be in equilibrium.

steady state or dynamic equilibrium: the state at which the competing rates of uptake and elimination of a chemical within an organism or tissue are equal. An apparent steady state is reached when the concentration of a chemical in tissue remains essentially constant during a continuous exposure.

stressor: any physical, chemical or biological substance or process arising from a pressure that has the potential to induce an adverse environmental response to a community value.

sublethal: involving an adverse effect below the level that causes death.

supersaturation: refers to a solution containing more solute than equilibrium conditions will allow.

suspension: a system in which very small particles (solid, semi-solid, or liquid) are more or less uniformly dispersed in a liquid or gaseous medium. If the particles are small enough to pass through filter membranes, the system is termed a colloidal suspension. If the particles are of larger than colloidal dimensions they will tend to precipitate, if heavier than the suspending medium, or to agglomerate and rise to the surface, if lighter.

synergism: a phenomenon in which the effect or toxicity of a mixture of chemicals is greater than that to be expected from a simple summation of the effects or toxicities of the individual chemicals present in the mixture.

tainting: refer to off-flavour.

taxa richness: number of taxa present.

taxon (taxa): any group of organisms considered to be sufficiently distinct from other such groups to be treated as a separate unit (e.g. species, genera, families).

taxonomic (group, resolution): an organism’s location in the biological classification system used to identify and group organisms with similar physical, chemical and/or structural composition.

thermodynamic equilibrium: property of a system which is in mechanical, chemical and thermal equilibrium.

thermotolerant coliform: also known as faecal coliforms. In tropical and sub-tropical areas, thermotolerant coliforms may on some occasions include microorganisms of environmental rather than faecal origin.

tolerance: the ability of an organism to withstand adverse or other environmental conditions for an indefinitely long exposure without dying.

total dissolved solids (TDS): a measure of the inorganic salts (and organic compounds) dissolved in water.

total metal: the concentration of a metal in an unfiltered sample that is digested in strong nitric acid.

toxicant: a substance capable of producing an adverse response (effect) in a biological system, which may seriously injure structure or function or produce death at sufficiently high concentration.

toxicity : the inherent potential or capacity of a material to cause adverse effects in a living organism.

toxicity identification and evaluation (TIE): toxicity characterisation procedures involving use of selective chemical manipulations or separations and analyses coupled with toxicity testing to identify specific classes of chemicals and ultimately individual chemicals that are responsible for the toxicity observed in a particular sample.

toxicity test: the means by which the toxicity of a chemical or other test material is determined. A toxicity test is used to measure the degree of response produced by exposure to a specific level of stimulus (or concentration of chemical) for a specified test period.

trophic level: a notional stage in the ‘food chain’ that transfers matter and energy through a community. Primary producers, herbivores, carnivores and decomposers each occupy a different trophic level.

true colour: the colour of water resulting from substances that are totally in solution; not to be mistaken for apparent colour resulting from colloidal or suspended matter.

turbulence: unorganised movement in liquids and gases resulting from eddy formation.

Type I error: probability of concluding that an impact has occurred when, in fact, an impact has not occurred

Type II error: probability of concluding that an impact has not occurred when, in fact, an impact has occurred.

univariate: statistical analysis concerned with data collected on one dimension of the same organism.

uptake: a process by which materials are absorbed and incorporated into a living organism.

value judgements: a decision involving basic issues of fairness, reasonableness, justice, or morality.

volatile: having a low boiling or subliming pressure (a high vapour pressure).

water quality: the physical, chemical and biological characteristics of water and the measure of its condition relative to the requirements for one or more biotic species and/or to any human need or purpose.

water quality objective: the guideline value and/or narrative statement for each selected indicator for water quality that should ensure the protection of all identified community values. Learn more about water quality objectives.

watertable: the level of groundwater; the upper surface of the zone of saturation for underground water.

weight of evidence (WoE): a qualitative, semi-quantitative or quantitative combination of multiple lines of evidence to make an overall assessment of water or sediment quality and/or associated management. This assessment incorporates judgments about the quality, quantity, relevance and congruence of the data contained in the different lines of evidence. Learn more about weight of evidence.

whole effluent toxicity testing: the use of toxicity tests to determine the acute and/or chronic toxicity of effluents.

xenobiotic: a foreign chemical or material not produced in nature and not normally considered a constituent of a specified biological system. This term is usually applied to manufactured chemicals.

zooplankton: the animal portion of the plankton.