The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). However, pI is also used. For brevity, this article uses pI. The net charge on the molecule is affected by pH of its surrounding environment and can become more positively or negatively charged due to the gain or loss, respectively, of protons (H+).
Clay is a type of fine-grained natural soil material containing clay minerals. Clays develop plasticity when wet, due to a molecular film of water surrounding the clay particles, but become hard, brittle and non–plastic upon drying or firing. Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of iron oxide.
Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Earth's body of soil, called the pedosphere, has four important functions:
Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the negative logarithm (base 10) of the activity of hydronium ions in a solution. In soils, it is measured in a slurry of soil mixed with water, and normally falls between 3 and 10, with 7 being neutral. Acid soils have a pH below 7 and alkaline soils have a pH above 7. Ultra-acidic soils and very strongly alkaline soils are rare.
Liming is the application of calcium- and magnesium-rich materials in various forms, including marl, chalk, limestone, burnt lime or hydrated lime. In acid soils, these materials react as a base and neutralize soil acidity. This often improves plant growth and increases the activity of soil bacteria, but oversupply may result in harm to plant life.
Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces.
Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite group, is a 2:1 clay, meaning that it has two tetrahedral sheets of silica sandwiching a central octahedral sheet of alumina. The particles are plate-shaped with an average diameter around 1 μm and a thickness of 0.96 nm; magnification of about 25,000 times, using an electron microscope, is required to "see" individual clay particles. Members of this group include, amongst others, saponite, nontronite, beidellite, and hectorite.
Ion exchange is a reversible interchange of one kind of ion present on an insoluble solid with another of like charge present in a solution surrounding the solid with the reaction being used especially for softening or making water demineralised, the purification of chemicals and separation of substances.
Ion chromatography separates ions and polar molecules based on their affinity to the ion exchanger. It works on almost any kind of charged molecule—including large proteins, small nucleotides, and amino acids. However, ion chromatography must be done in conditions that are one unit away from the isoelectric point of a protein.
A carboxylate is the conjugate base of a carboxylic acid, RCOO−. It is an ion with negative charge.
The point of zero charge (pzc) is generally described as the pH at which the net charge of total particle surface is equal to zero, which concept has been introduced in the studies dealt with colloidal flocculation to explain pH affecting the phenomenon.
Soil chemistry is the study of the chemical characteristics of soil. Soil chemistry is affected by mineral composition, organic matter and environmental factors. Back in the early 1850s a consulting chemist to the Royal Agricultural Society in England, named J. Thomas Way, performed many experiments on how soils exchange ions. As a result of his diligent and strenuous work, he is considered the father of soil chemistry. But after him, many other big-name scientists also contributed to this branch of ecology including Edmund Ruffin, Linus Pauling, and many others.
Alkali, or Alkaline, soils are clay soils with high pH, a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swell and difficult to clarify/settle. They derive their name from the alkali metal group of elements, to which sodium belongs, and which can induce basicity. Sometimes these soils are also referred to as alkaline sodic soils.
Alkaline soils are basic, but not all basic soils are alkaline.
Acid-neutralizing capacity or ANC in short is a measure for the overall buffering capacity against acidification of a solution, e.g. surface water or soil water.
Sand-based athletic fields are sports turf playing fields constructed on top of sand surfaces. It is important that turf managers select the most suitable type of sand when constructing these fields, as sands with different shapes offer varied pros and cons. Regular maintenance of sand-based athletic fields is just as important as the initial construction of the field. As water and other aqueous solutions are added, a layer of thatch may accumulate on the surface of the turf. There are different ways to manage this level of thatch, however the most common are aeration and vertical mowing.
An ion is an atom or molecule with a net electrical charge.
Anion-exchange chromatography is a process that separates substances based on their charges using an ion-exchange resin containing positively charged groups, such as diethyl-aminoethyl groups (DEAE). In solution, the resin is coated with positively charged counter-ions (cations). Anion exchange resins will bind to negatively charged molecules, displacing the counter-ion. Anion exchange chromatography is commonly used to purify proteins, amino acids, sugars/carbohydrates and other acidic substances with a negative charge at higher pH levels. The tightness of the binding between the substance and the resin is based on the strength of the negative charge of the substance.
Clay chemistry is an applied subdiscipline of chemistry which studies the chemical structures, properties and reactions of or involving clays and clay minerals. It is a multidisciplinary field, involving concepts and knowledge from inorganic and structural chemistry, physical chemistry, materials chemistry, analytical chemistry, organic chemistry, mineralogy, geology and others.
Soil aggregate stability is a measure of the ability of soil aggregates to resist degradation when exposed to external forces such as water erosion and wind erosion, shrinking and swelling processes, and tillage. Soil aggregate stability is a measure of soil structure and can be impacted by soil management.
The soil matrix is the solid phase of soils, and comprise the solid particles that make up soils. Soil particles can be classified by their chemical composition (mineralogy) as well as their size. The particle size distribution of a soil, its texture, determines many of the properties of that soil, in particular hydraulic conductivity and water potential, but the mineralogy of those particles can strongly modify those properties. The mineralogy of the finest soil particles, clay, is especially important.
