Amount of water vapor contained in the atmosphere. “Relative humidity” is the ratio, usually expressed as a percent, of the amount of water vapor in the atmosphere to the maximum water vapor in the atmosphere possible at a specific temperature. “Absolute humidity” is the mass of water vapor per unit of dry air. When unspecified, reference is usually being made to relative humidity.
A process involving the decay of plant and microorganism matter to produce thenatural organic matter (NOM) as found in some soils, sediments, peats, coals, and shales. Plantlignin, related transformation phases, polysaccharides, melanin, cutin, proteins, lipids, nucleic acids, and fine char particles, are materials involved in humification.
Cf., fulvic acid, humic acid, humic substances, humin
Humin occurs as a result of the decay of plants and microorganisms in some soils, sediments, peats, coals, and shales, but not aquatic waters (humin is not soluble in water). Humin may be formed also in the dehydration of some sugars. Humin, along with fulvic acid and humic acid, is a humic substance. However, humin cannot be extracted from humic substances with either a strong base or a strong acid, whereas fulvic or humic acids can be extracted.
Cf., fulvic acid, humic acid, humic substances, humification
See opal.
In geotechnical engineering, hydraulic conductivity refers to the ease of fluid flow (for example, permeability) through sediment, rock or soil, and is affected by the viscosity of the fluid (water).
Cf., permeability
In an aquifer, the ratio of total hydraulic head loss (or difference) to the length of flow path in a given direction, or in a simple description, the slope of the surface of the water table.
The hydraulic head is the total energy of moving water (including porewater or groundwater), usually represented by the height of water column with a unit of length. The total hydraulic head is the summation of the velocity head (kinetic energy), pressure head (potential energy), and elevation head (potential energy), all converted to the height of the equivalent water column: h = hv + hp + hE = v2/2g + u/γw + z, where h is the total hydraulic head, and subscripts V, P, and E denote velocity, pressure, and elevation; v is the velocity; g gravity, u water/fluid pressure, γw unit weight of water at 25oC, and z elevation.
A regular interstratification of biotite-like layers with vermiculite-like layers. The ratio of vermiculite-like layers (i.e., one 2:1 layer and one interlayer capable of limited swelling) to biotite (i.e., one 2:1 layer) is 1:1 (Brindley et al., 1983).
The hydrogen (H) atom in solids is often asymmetrically located between an electronegative donor atom (D) and an electronegative acceptor (A) atom, such that the D-H distance is smaller than the H-A distance. The H atom can penetrate the electron cloud of the donor atom. The D-H–A configuration may be linear or bent, and there may be multiple A atoms. The overall bond is considered essentially ionic in character, with an overall bond strength (for D-H–A configurations) considerably weaker than a (sigma) covalent bond but considerably stronger than van der Waals interactions. The H atom may serve to balance overall charge, for example as an O-H in oxygen-based structures, in which case the H does not link a donor to an acceptor atom.
A discredited term for a mixture of hausmannite and feitknechtite (beta-MnOOH).