S&W definitions

Question	Answer
Pollution	making something impure and harmful by adding another substance.
Contamination	making something impure by adding another substance.
Brownfield	abandoned land that’s available for building development and which is (potentially) contaminated by industrial and commercial activities.
Primary pollutants	pollutants that cause harmful effects in the form in which they are released into the environment.
Secondary pollutants	pollutants that are formed as a result of a chemical process in the environment, often from less harmful precursors.
Background concentration	a substance’s natural concentration in soil or water (so without human interference).
Point source	direct releases of pollutants from a single location. Mostly confined to a plume in the downstream direction from the source. In general, easily monitored and controlled because they can often be identified as being caused by a particular individual or organisation.
Diffuse source	a pollutant release that occurs over a wide area, non-point source. Pollutant gradients are usually gradual. Possibly a cumulative effect of multiple undistinguishable point sources.
Toxicity	the capacity to cause harm to a living organism. Measurable in LD50/LC50, ED50/EC50, NOEL/NOED/NOEC.
LD50 / LC50	Median lethal dose/concentration. It describes the level of exposure that kills 50% of the population.
ED50 / EC50	Median effect dose/concentration. It describes the level of exposure that causes a defined effect to 50% of the population.
NOEL / NOED / NOEC	no observed effect level/dose/concentration. Level at which a test chemical does not cause an effect that is statistically significantly different from the control.
Bioavailability	the rate and extent to which a substance can be taken up or absorbed into the tissues of organisms and so influence their physiology. It is the most important factor determining the extent to which a contaminant in soil and water wil enter the food chain.
Bioaccumulation	the extent to which pollutants accumulate over time in the tissues of organisms through any route, including respiration, ingestion, or direct contact.
Biological half-life	the time it takes to remove 50% of the quantity of a substance in a specific tissue organ, or any other specified biota as a result of biological processes.
Biomagnification	the increase in concentrations as the pollutant passes through the food chain.
Speciation	the occurrence of different forms, whether chemical or physical, of an element. It determines its bioavailability and toxicity and controls its transport and fate in soil and water.
TDS	total dissolved solids
Electrical conductivity	a measure of the water’s ability to conduct electricity and therefore measure of the water’s ionic concentration.
Activity	a concentration corrected for the non-ideal effects in aqueous salutation arising from the electrostatic forces between all dissolved ions in the water.
Phase	distinct and homogeneous state of a material with no visible boundary separating it into parts.
Partition coefficient Distribution coefficient	ratio between the concentration in the adsorbed phase and the concentration in the dissolved phase.
Henry's law KH	the ratio for portioning among the aqueous and gas phase in equilibrium.
Octanol-water partitioning coefficient Kow	the ratio between the concentration of a chemical in octanol and in water at equilibrium and at a specified temperature and is a measure of the tendency of chemical to partition itself between the aqueous phase and organic phase.
Octanol	an organic solvent used as a surrogate for natural organic matter.
Isotherm	GRAPH OF TEMPERATURE Freundlich isotherm Cs = K Cwn Langmuir isotherm Cs = (Q0K Cw)/(1+K Cw)
Adsorbent	the substrate onto which a substance is sorbed.
Adsorbate	substance that becomes adsorbed.
Fugacity	the tendency of a substance to flee from the phase it is in.
Solubility	the concentration of the saturated solution at a given temperature and pressure.
Solubility product	the equilibrium constant for dissolution-precipitation reactions.
Buffered solution	solution that is barely sensitive to changes in their pH as a result of the addition of moderate quantities of strong acids or strong bases.
Reductant	electron donor.
Oxidant	electron acceptor. A substance that causes oxidation by accepting electrons from a reductant, while being reduced itself.
Redox potential	the tendency of the system to donate of accept electrons.
pH-Eh diagram	a two-dimensional graph. The fields of stability or dominance of both dissolved species and minerals as function of the pH and Eh are indicated, whereby the dominant stable species can be recognized directly and easily.
Vadose zone	the unsaturated zone
Preferential flow	heterogeneous soil properties that govern soil water flow.
Aquifer	a water-yielding rock formation that contains and is able to transmit sufficient groundwater to be a source of water supply.
Aquitard	a layer of low permeability.
Aquiclude	an impermeable body of rock.
Phreatic aquifer	bounded from above by a phreatic surface (the surface at every point of which the pressure in the water equals the atmospheric pressure)
Perched aquifer	phreatic aquifer formed on a semi-permeable, or impermeable layer below which unsaturated material is present.
Confined aquifer	bounded by aquitard or aquiclude at both the top and bottom.
Artesian aquifer	confined aquifer that is characterized by an hydraulic head that is higher than the local ground surface level so that water can flow out of wells without any need for pumps.
Groundwater	the water present in the saturated zone beneath the water table.
Recharge	the replenishment of groundwater.
Hydraulic conductivity	the ability of the porous material to transmit water and is largely determined by the texture of the porous material.
Surface water	all water on the surface of the Earth found in rivers, streams, canals, ditches, ponds, lakes, marshes, wetlands, coastal and marine water, and as ice and snow.
Hyporheic zone	the zone of bed sediments.
Epilimnion	he upper, well-mixed, warm layer of a water body.
Hypolimnoin	the lower, cold layer of a deep water body caused by thermal stratification.
Thermocline	the zone of rapid temperature change between the epilimnion and the hypolimnion.
Colloids	a special intermediate case between dissolved and particulate matter. They consist of particles dispersed in water.
Sesquioxides	mineral structure of Al and Fe oxides/hydroxides.
PZC	point of zero charge, the pH at which the charge of the mineral surface is neutral.
Diffuse layer	the soil solution near the mineral surface. In this layer, the cations are more abundant than diffuse anions. These cations are thus not bonded to the surface but are in solution.
Stern layer	a layer in which cations are sorbed directly at the surface.
Diffuse double layer	consists of the diffuse layer and the stern layer. Zone near negatively charged surfaces of colloids.
CEC	Cation Exchange Capacity, the extent to which clay minerals are able to exchange cations.
AEC	Anion Exchange Capacity, the extent to which clay minerals are able to exchange anions.
Flocculation	the formation of flocs or aggregates.
Detritus	undecayed dead plant and animal tissue.
Humic substances	decomposed detritus by microorganisms. It is amorphous, colloidal, polymeric, dark-brown organic compounds with a high molecular weight.
Humification	the formation of humic substances.
Mineralisation	the complete breakdown to inorganic compounds, mainly water and CO2, but also other minerals and nutrients that constitute an essential part of organic matter.
Humin	the portion of humus that is insoluble in the dilute sodium hydroxide. The part that dissolves in solution consists of humic acid and fulvic acids. Fulvic acids have lower molecular weight than humic acids (= difference).
DOM	dissolved organic matter, approximately similar to the soluble organic matter present in soils.
POM	particulate organic matter, consists largely recalcitrant remains and woody terrestrial and aquatic plants.
Ligands	organic or inorganic ion that can form complexes with metal-ions by two or more contacts.
Chelation	the formation of a complex between a metal and an organic ligand.
Denitrification	the process where nitrate is transformed into free nitrogen gas. It is taken through intermediates like nitrite, nitric oxide, and nitrous oxide.
BOD	biochemical oxygen demand, the amount of dissolved oxygen used up by a water sample in darkness (at room temperature for five days)/ measure for the amount of easily degradable organic matter in water.
COD	chemical oxygen demand, the amount of oxygen consumed in the complete oxidation of carbonaceous matter.
SOD	sediment oxygen demand, the rate of the dissolved oxygen consumption in a water body due to the decomposition of sediment organic matter.
Major dissolved phase constituents	substances that are abundant as dissolved ions in natural waters.
Stiff diagram	diagram that expresses the concentrations of cations and anions.
Piper diagram	two triangular graphs that display the relative contribution or various cations and anions to the respective total positive and negative charge and a diamond shaped graph that combines these contributions of cations and anions.
TIC	total inorganic carbon, consists of carbonic acid (H2CO3), hydrogen carbonate or bicarbonate (HCO3-) and carbonate (CO3 2-).
Alkalinity	the capacity to neutralize acid.
Nutrients	the raw materials that are assimilated by living organisms to promote growth, development and reproduction.
Nutrient cycling	all the processes by which nutrients are transferred from one organism to another.
Trophic levels	the position of the organism in the food chain of food web.
Eutrophication	accelerated nutrient cycling due to enhanced external nutrient inputs.
Ammonium fixation	the process by which clay minerals capture ammonium tightly between the mineral lattices. Mostly irreversibly bonded.
Nitrogen fixation	the process where bacteria on plants fix nitrogen from the atmosphere.
Ammonification	The formation of ammonium as a result of the breakdown of organic nitrogen by oxidation.
Nitrification	the process where autotrophic bacteria oxidise ammonium to nitrate under oxic condition. This process has multiple steps. It requires oxygen to occur.
Immobilisation	microorganisms utilise substantial quantities or inorganic nitrogen that thereby become part of organic matter. It is the opposite process of mineralization.
Dry deposition	removal of gases and aerosols from the atmosphere without the interference of precipitation.
Wet deposition	wash-out of gases and aerosols from the atmosphere in solution by precipitation.
Occult deposition	removal of gases and aerosols from the atmosphere through diffusion across the interface between air and wet surface, in fog and dew drops.
Phosphate fixation	the interactions of phosphates with iron, aluminum, sesquioxides and calcium. Adsorption of phosphate to soil or sediment minerals.
Internal loading	the release of dissolved constituents (mostly nutrients) from lake/river bed sediments.
Heavy metals	metals and semimetals that have been associated with contamination and potential toxicity or ecotoxicity.
Coprecipitation	the inclusion of additional species within or on the surface of a precipitate as it is formed.
Ionising radiation	any radiation which displaces orbital electrons from atoms, so producing ions.
Isotopes	atoms that have the same number of protons but different numbers of neutrons.
Alpha radiation	radiation consisting of positively charged helium nuclei.
Beta radiation	radiation consisting of electrons or positions.
Gamma radiation	radiation consisting of a discrete quantity of electromagnetic energy without mass or charge.
Background radiation	the sum of terrestrial radiation, cosmogenic radiation and the portion of cosmic radiation that reaches the Earth’s surface.
Nuclear fission	the break-up of heavy elements into smaller nuclei through bombardment with neutrons in a nuclear fission reactor.
Neutron activation	the process of capture of neutrons in the nuclei of elements.
Organic pollutant	a variety of compounds made up of C, H, O and small amounts of N, P, S and Cl.
VOC's	volatile organic compounds. Organic pollutant that evaporates readily and completely when exposed to the atmosphere.
SVOC's	semi volatile organic compounds. Organic pollutants that evaporate slowly and partially when exposed to the atmosphere.
POP's	persistent organic pollutants. Organic compounds that break down very slowly in the environment.
Isomers	substances that can be structured spatially in more than one manner.
Aromatic	compounds containing at least one benzene ring structure.
Aliphatic	hydrocarbons that are not aromatic.
LNAPL's	light non-aqueous phase liquids. Less dense than water.
DNAPL's	dense non-aqueous phase liquids. Denser than water.
Monocyclic aromatic hydrocarbons	compounds consisting solely of carbon and hydrogen and containing one benzene ring. Also: BTEX (benzene, toluene, ethylbenzene, xylene).
Polycyclic aromatic hydrocarbons	compounds consisting solely of carbon and hydrogen and containing two or more benzene rings. Also: PAH’s.
Chlorinated hydrocarbons	hydrocarbons with one or more chlorine substituents. They can consist of aliphatic as well as aromatic structures.
ESOC's	Emerging Substances Of Concern. Substances that have recently been detected in the environment or recognized as potentially toxic.
Protonation	adsorption of protons (H+ ions) at the surface of sesquioxides or clay minerals.

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	Created by Denise Catsman over 2 years ago