Glossary of Terms

A measure of the buffering capacity of the water, and since pH has a direct effect on organisms as well as an indirect effect on the toxicity of certain other pollutants in the water, the buffering capacity is important to water quality. The alkalinity of many surface waters is primarily a function of carbonate, bicarbonate and hydroxide content. Alkalinity is measured using the SmartChem Discrete Wet Chemistry Analyzer.
Is present naturally in surface and wastewaters. Its concentration is low in groundwaters because it adsorbs to soil particles and clays and is not leached readily from soils. It is produce by the breakdown of organic nitrogen compounds. High levels of ammonia in surface waters stimulate algae growth but are also toxic to fish.
The lowest reasonably accurate concentration of an analyte that can be detected by an analytical process; this value varies depending on the method, instrument and dilution used.
Ash is the mineral content of a product remaining after complete combustion.
Chemical analysis performed by atomizing a sample (water, extract or digest solution) in a flame and measuring the absorbance of light by the atomic species. This technique is based on the Beer-Lambert law that states that the absorbance of an atomic species is directly proportional to the concentration of the absorbing species & the path length through which the light passes. The AAS is used to analyze samples for cation metals, for example, Na, Ca, Mg, K, Cu, Al, Fe, Mn, & Li.
All of the living material in a given area; biomass often refers to vegetation.
A quality assurance sample in which the laboratory performing the analysis is unaware of the sample's true concentration. This sample may be collected as a duplicate or may be a sample spiked with known concentrations of a specific analyte.
A buffered soil contains enough lime or base saturation to resist change in pH, especially toward acidity. Sandy soils with low CEC (cation exchange capacity) are low in buffering capacity; clay soils with high exchange capacity are highly buffered.
Soil bulk density (Db) is the ratio of the dry weight of soil to its undisturbed volume. It provides a measure of soil porosity and compaction. Db is expressed in grams/cubic centimeter. As Db increases, the soil porosity decreases.
Colloids are small soil particles with diameters ranging from 0.005 – 0.200 microns. Colloids in soil (clay and humus) are characterized by high cation exchange due to their large surface area per mass.
Interchange of a cation (positive ion) in the soil solution with another cation on the surface of colloidal clay or humus. Essential nutrient cations in the soil colloids include Ca, Mg, K and non-essential nutrients cations like H, Al and Na. Cations on the soil colloids are referred to as 'exchangeable' because they can be available for plant growth.
CEC refers to the total number of cations a soil can adsorb through cation exchange. CEC is usually expressed as milliequivalents (meq) per 100 grams of soil. Sandy (coarse) soils usually have a low CEC. As the soil texture becomes finer, CEC values generally increase. Soils also increase in CEC with an increase in organic matter content. CEC values are also affected by the type and amount of clay present. The young expandable clays such as montmorillonite and vermiculite generally have higher CEC values than older nonexpanding clays like kaolinites and illites.
Conductivity measures the ability of a solution to carry an electrical current. This ability depends on the presence of ions. Soil solution conductivity is often expressed in milliSiemens/cm. The conductivity of water is often expressed in microSiemens/cm.
A non-discrete sample composed of more than one specific aliquot collected at various sampling points or times.
A unit of conductivity equal to mmhos/cm.
The biochemical decomposition of organic matter, resulting in partial gasification, liquefaction, and mineralization of pollutants.
Prepared by passing feed water through a mixed-bed ion exchanger, consisting of strong anions and strong cations resins mixed together. The resultant water should meet the following criteria:
  • Resistivity (megohm-cm @ 25°C) > 18
  • Conductivity (µmho/cm @ 25 °C) < 0.1
  • Total oxidizable organic carbon (mg/L) < 0.05
  • Total solids (mg/L) ≤ 0.1&
  • SiO2 (mg/L) less than 0.05
The biological reduction of nitrate to nitrogen gas by denitrifying bacteria in soil.
Disintegrated organic and inorganic material in water. Excessive amounts make water unfit to drink or use in industrial processes.
The weight (g) of an ion or compound that combines with or replaces 1 gram of hydrogen. The atomic weight or formula weight divided by its valence.
The solution that results from combining a soil extractant and the soil.
The solvent or chemical used to bring available nutrients into solution out of the soil. Extractants are formulated to dissolve out specific substances, depending on analytical requirements.
The sodium in a soil held by the negative charges of the soil colloids. As soils increase in exchangeable sodium, they become progressively less permeable to water.
A simple test using acid to determine if a soil has an excess of carbonates. The test is positive if effervescence (fizzing) occurs when acid is added to the soil sample.
A measure of the amount of clay dispersion in a soil. Calcium and Magnesium tend to open (flocculate) soils. Sodium tends to close (deflocculate) the soil.
Analytical technique for separating, identifying, and quantitating organic compounds in samples. Target compounds are extracted into a suitable organic solvent, injected into a gas chromatograph and separated based on analyte polarity or molecular size as they are carried along the length of a chromatographic column by the carrier gas. Individual analytes elute into a detector and are measured based on electronic deflection from an established baseline. The compounds are identified usually based on retention time compared to a known standard. Samples are quantitated, again based on comparison to the detector response of a known standard.
The organic matter that remains after initial decay of plant and animal tissues. Most of the soil N is stored in the humus. As humus slowly decays, nitrogen is released and becomes available to plants. Humus is about 5% nitrogen by weight.
IC is a liquid chromatographic technique in which the ionic components of a sample are separated into discrete bands by passing the sample through a column filled with specially-designed ion exchange resin. Once separated, the individual ions are detected, identified, and quantitated.
The loss on ignition at 375°C is an estimate of organic matter in non-calcareous soils. This method gives quantitative oxidation of organic matter, but other soil constituents may be altered or destroyed in the process, thus resulting in weight losses in excess of the actual organic content.
milliequivalent of an ion or a compound in 1L of solution. This unit is often used in irrigation water analysis to quantify the concentration of cations and anions.
The milligram formula weight of an ion or ionic compound divided by its valence.
The transformation of a nutrient from organic to inorganic form by microbes in the soil.
The process whereby ammonia is oxidized to nitrite and then to nitrate by bacteria or chemical reaction.
While nitrate is much less toxic than ammonia or nitrite, levels over 30 ppm of nitrate can inhibit growth, impair the immune system and cause stress in some aquatic species. In most cases of excess nitrate concentrations, the principle pathway of entering aquatic systems is through surface runoff from agricultural or landscaped areas which have received excess nitrate fertilizer. These levels of nitrate can also lead to algae blooms. Consequently, as nitrates form a component of total dissolved solids, they are widely used as an indicator of water quality.
Is an intermediate oxidation state of nitrogen. It can enter a water supply system through its use as a corrosion inhibitor in industrial process water, or through incomplete oxidation of ammonia.
Is the measurement of the proportions of various sizes of primary soil particles in a soil sample. It is determined usually either by their capacities to pass through sieves of various mesh size or by their rates of settling in water.
  • Sand - A soil mineral particle that is between 0.05 and 2.0 mm in diameter - Contains 85% or more sand and not more than 10% clay
  • Silt - A soil mineral particle between 0.002 and 0.05 mm in diameter - Contains 80% or more silt and less than 12% clay.
  • Clay - A soil particle with an average diameter of less than 2 microns (0.002 mm). Soil clays are colloidally active and have a negative surface charge that attracts and holds positive ions. - Contains less than 40% sand, less than 40% silt and greater than 40 % clay.
The percentage of the cation exchange capacity that is due to base cations (Ca, K, Na and Mg)
Is a measure of the soil/water acidity, neutrality, or alkalinity . It is one of the best diagnostic measurements available to identify soil conditions.
  1. Acid soils: Have a pH well below 6. These soils lose productivity due to low nutrient availability and presence of toxic ions such as Al.
  2. Alkaline soils: Have a pH above 7.5. These soils can be sub-classed as calcareous or salt affected.
  3. Calcareous Soils: Contain high amount of free lime (CaCO3). The pH of these soils is usually between 7.5 and 8.5.
  4. Salt affected Soils: Soils contains high concentrations of soluble salts (saline) and/or exchangeable sodium (sodic).
A mixture of soil and water. At saturation, the soil paste will glisten, flow slightly, when the container is tipped, the paste will slide freely and cleanly from the spatula (except soils with high clay content).
Topsoil, sand and minerals washed from the land into water, usually after rain or snow melt.
A semi-solid residue from any of a number of air or water treatment processes that can be considered a hazardous waste.
A watery mixture of insoluble matter resulting from certain pollution control techniques.
The colorimetric determination of major soil nutrients is performed using a SmartChem Discrete Wet Chemistry Analyzer. Quantitation is based on Beer-Lambert's law (see AAS below). In agriculture, the analyzer is used for determining levels of nitrate, nitrite, ammonium and phosphate in plant, soil and water samples. The instrument can also be used to determine levels of Chloride, Sulfate, and carbonate in solution. Samples are reacted with color-producing reagents and the absorbance of the colored solution is determined at wavelengths specific to the color produced.
The water contained in the pore space of the unsaturated zone.
Small particles of solid pollutants that float on the surface of, or suspended in, sewage or other liquids.
A measure of the percentages of various particles size groups in a volume of soil; typically sand ,silt and clay.
A ratio that expresses the relative activity of sodium ions in exchange reactions with soil.
plowing, seedbed preparation and cultivation practices.
Total filterable residue.
Total non-filterable residue.
The amount of exchangeable H+ and Al3+ in a soil.
NPOC (non-purgeable Organic Carbon) is a direct measurement of TOC. In this type of analysis, acid is added to the sample and the solution is sparged with oxygen until the purgeable organic carbon (POC) and inorganic carbon (IC) are removed. The NPOC is then reduced in the combustion tube to form carbon dioxide, which is detected by the NDIR (non-dispersive infrared detector).
In this type of analysis, the sample passes through the combustion tube where the TN in the sample thermally decomposes to create nitrogen monoxide. The nitrogen monoxide is cooled and dehumidified before passing into a Chemiluminescence detector.