Lexikon

soils support a number of inorganic and organic chemical reactions. Many of these reactions are dependent on some particular soil chemical properties. One of the most important chemical properties influencing reactions in a soil is pH. Soil pH is primarily controlled by the concentration of free hydrogen ions in the soil matrix. Soils with a relatively large concentration of hydrogen ions tend to be acidic. Alkaline soils have a relatively low concentration of hydrogen ions. Hydrogen ions are made available to the soil matrix by the dissociation of water, by the activity of plant roots, and by many chemical weathering reactions.

Soil fertility is directly influenced by pH through the solubility of many nutrients. At a pH lower than 5.5, many nutrients become very soluble and are readily leached from the soil profile. At high pH, nutrients become insoluble and plants cannot readily extract them. Maximum soil fertility occurs in the range 6.0 to 7.2.

Determination of soil pH is a complicate matter: we have to add water to be able to measure the pH, with this we dilute the soil (and the hydrogen ions to be measured) and we initiate the dissolution of normally particulate solid matter, which may modify the pH (for example, limestone). The whole procedure is time dependent.

soil remediation based on aerobic biodegradation is an oxidative process catalysed by microbes. Microbes, mainly bacteria utilise the contaminant as substrate for producing energy. Aerobic bacteria use athmospheric oxigen for the oxidation of the polluting organic compounds and produce inorganic products, such as CO₂, NO₃ and H₂O. This process is also called mineralisation.

When athmospheric oxigen is limited, the biodegradation is catalysed by facultative anaerobic microbes, which use NO₃ for their alternative respiration. In this case the oxidation/mineralisation products from the substrate the contaminant are alcohols or aldehydes.

anaerobic biodegradation of soil contaminants is based on the aternative respiration of soil microorganisms, using oxigen from NO₃^2-, SO₄^2-or CO₂, as hydrogen-acceptor instead of atmospheric oxigen. Paralel to the oxidation of the contaminant energy source in this case, nitrate, sulfate and carbonate are reduced into N₂ via nitrite NO₂⁻, nitric oxide NO, nitrous oxide N₂O, H₂S and CH₄ respectively.

There are some metals which can also be reduced and function as electronacceptor, such as ferric ion Fe³⁺reduction to Fe²⁺ or Fe⁰, manganic ion Mn⁴⁺ reduction to Mn²⁺, selenate SeO₄^2- reduction to selenite: SeO₃^2- and Se⁰, arsenate AsO₄^3- reduction to arsenite: AsO₃^3- or uranyl ion UO₂²⁺ reduction to uranium dioxide UO₂ for the electron transport chain.

The anaerobic biodegradation of xenobiotics needs a microorganism- and metabolism-specific redoxpotential. The soil remedial biotechnology is responsible for ensuring the proper redoxpotential in the soil to control the process and run biodegradation on the optimum.

To control the redoxpotential the technologist should ensure sufficient quantity of nitrate, sulfate or any other electronacceptors in the soil.

solidification/stabilisation (S/S) is a process which physically binds or encloses contaminants within a stabilised mass and is performed both ex situ and in situ. This technology reduces the mobility of hazardous substances and contaminants in the environment through both physical and chemical means.

Ex situ S/S requires excavation of the material to be treated, and the resultant material must be disposed.

In situ S/S uses auger/caisson systems and injector head systems to add binders to the contaminated soil or waste without excavation, and the resultant material is left in place.

soil texture is a soil property used to describe the relative proportion of different grain sizes of mineral particles in a soil. Particles are grouped according to their size into what are called soil separates. These separates are typically named clay, silt, and sand. Soil texture classification is based on the fractions of soil separates present in a soil. The soil texture triangle is a diagram often used to figure out soil textures.

(Source: Wikipedia)

soil value marks are used in a Hungarian system for the characterisation of agricultural soil quality by a decimal mark system. 0−9 marks for the characteristics, and further 0−9 marks for the quality within each characteristics. The highest value is 100 and the productivity of the soil which is characterised by the marks is equivalent with the % of the maximum.

soil vapor extraction SVE is used to remediate unsaturated vadose zone soil. A vacuum is applied to the soil to induce the controlled flow of air and remove volatile and some semivolatile organic contaminants from the soil. SVE usually is performed in situ; however, in some cases, it can be used as an ex situ technology.

soil washing is an ex situ soil or sediment treatment technology. Contaminants sorbed onto fine soil particles are separated from bulk soil in a water-based system on the basis of particle size. The wash water may be augmented with a basic leaching agent, surfactant, or chelating agent or by adjustment of pH to help remove organics and heavy metals. Soils and wash water are mixed ex situ in a tank or other treatment unit. The wash water and various soil fractions are usually separated using gravity settling.

Soil washing is an ex situ soil or sediment treatment technology. Contaminants sorbed onto fine soil particles are separated from bulk soil in a water-based system on the basis of particle size. The wash water may be augmented with a basic leaching agent, surfactant, or chelating agent or by adjustment of pH to help remove organics and heavy metals. Soils and wash water are mixed ex situ in a tank or other treatment unit. The wash water and various soil fractions are usually separated using gravity settling.

soil water is held in the pore spaces between particles of soil. Soil water is the water that is immediately available to plants. Soil water can be further sub-divided into three categories, 1) hygroscopic water, 2) capillary water, and 3) gravitational water.

Hygroscopic water is found as a microscopic film of water surrounding soil particles. This water is tightly bound to a soil particle by molecular attraction so powerful that it cannot be removed by natural forces. Hygroscopic water is bound to soil particles by adhesive forces that exceed 31 bars and may be as great as 10,000 bars (Recall that sea level pressure is equal to 1013.2 millibars which is just about 1 bar!).

Capillary water is held by cohesive forces between the films of hygroscopic water. The binding pressure for capillary water is much less than hygroscopic water. This water can be removed by air drying or by plant absorption, but cannot be removed by gravity. Plants extract this water through their roots until the soil capillary force (force holding water to the particle) is equal to the extractive force of the plant root. At this point the plant cannot pull water from the plant-rooting zone and it wilts (called the wilting point).

Gravity water is water moved through the soil by the force of gravity. The amount of water held in the soil after excess water has drained is called the field capacity of the soil. The amount of water in the soil is controlled by the soil texture. Soils dominated by clay-sized particles have more total pore space in a unit volume than soils dominated by sand. As a result, fine grained soils have higher field capacities than coarse-grained soils.

There is a relationship between soil texture, wilting point, field capacity, and available water. The difference between the wilting point and the field capacity is the available water. The smallest amount of available water is associated with the coarsest soil texture, sand. The amount of available water increases where soils with a mixture of different sized particles (loamy soils) are found. The available water then drops off toward the fine textured soils on the right. How does one explain the relationship between available water and soil texture? Coarse soil does not have much available water because it doesn't hold much water to begin with. At the other end of the spectrum, low available water in fine soils is due to strong bond between soil particles and water. Plants have a harder time pulling water away from the soil particle under these conditions.

soil is generally defined as the top layer of the earth’s crust. It is formed by mineral particles, organic matter, water, air and living organisms. Soil is the interface between the earth (geosphere), the air (atmosphere) and the water (hydrosphere). While soil is the physical upper layer of what is usually referred to as “land”, the concept of “land” is much wider and includes territorial and spatial dimensions. It is difficult to separate soil from its land context. (Source: EUGRIS)

solar photovoltaics (PVs) are arrays of cells containing a material, such as silicon, that converts solar radiation into electricity. Today solar PVs are used in a wide range of applications, from residential rooftop power generation to medium-scale utility-level power generation.

The Concentrated Solar Power (CSP) systems use mirrors or reflective lenses to focus sunlight on a fluid to heat it to a high temperature. The heated fluid flows from the collector to a heat engine where a portion of the heat is converted to electricity. Some types of CSP allow the heat to be stored for many hours so that electricity can be produced at night.

the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, andsolar radiation is obvious as daylight when the Sun is above the horizon.

Sunlight is a key factor in photosynthesis, a process vital for life on Earth. The existence of nearly all life on Earth is fueled by light from the sun. Most autotrophs, such as plants, use the energy of sunlight, combined with minerals and air, to produce simple sugars—a process known as photosynthesis. These sugars are then used as building blocks and in other synthetic pathways which allow the organism to grow.

Heterotrophs, such as animals, use light from the sun indirectly by consuming the products of autotrophs, either directly or by consuming other heterotrophs. The sugars and other molecular components produced by the autotrophs are then broken down, releasing stored solar energy, and giving the heterotroph the energy required for survival. This process is known as respiration.

The more recent discoveries of coal, petroleum and natural gas are modern extensions of this trend. These fossil fuels are the remnants of ancient plant and animal matter, formed using energy from sunlight and then trapped within the earth for millions of years.

Solar energy arrives on the surface from two sources: direct sunlight and diffuse background-radiation from the sky. The solar constant of the radiation on the outer border of the atmosphere is 8,123 Jcm^-2min^-1, but out of this only 5.44 Jcm^-2min^-1 can reach the surface (see level), because the difference is reflected into space (albedo). Decrease of albedo (for example due to CO₂ accumulation in the atmosohere) causes an increase in the temperature of Earth (green-house effect).

The spectrum of the Sun's solar radiation is close to that of a black body with a temperature of about 5,800 K. About half that lies in the visible short-wave part of the electromagnetic spectrum and the other half mostly in the near-infrared part. Some also lies in the ultraviolet part of the spectrum. When ultraviolet radiation is not absorbed by the atmosphere or other protective coating, it can cause damage to the skin known as sunburn or trigger an adaptive change in human skin pigmentation.

The spectrum of electromagnetic radiation striking the Earth's atmosphere is 100 to 10⁶ nanometers (nm). This can be divided into five regions in increasing order of wavelengths:

• Ultraviolet C or (UVC) range, which spans a range of 100 to 280 nm.
• Ultraviolet B or (UVB) range spans 280 to 315 nm. I
• Ultraviolet A or (UVA) spans 315 to 400 nm.
• Visible range or light spans 400 to 700 nm. For the photosynthesis useful range is 380 nm to 740 nm.
• Infrared range that spans 700 nm to 10⁶ nm [1 mm]. It is responsible for an important part of the electromagnetic radiation that reaches the Earth. It is also divided into three types on the basis of wavelength:
  • Infrared-A: 700 nm to 1,400 nm
  • Infrared-B: 1,400 nm to 3,000 nm
  • Infrared-C: 3,000 nm to 1 mm.

a solar thermal collector is a solar collector designed to collect heat by absorbing sunlight. The term is applied to solar hot water panels, but may also be used to denote more complex installations such as solar parabolic, solar trough and solar towers or simpler installations such as solar air heat. The more complex collectors are generally used in solar power plants where solar heat is used to generate electricity by heating water to produce steam which drives a turbine connected to an electrical generator. The simpler collectors are typically used for supplemental space heating in residential and commercial buildings. A collector is a device for converting the energy in solar radiation into a more usable or storable form.

Flat plate thermal system for water heating deployed on a flat roof. They consist of a dark flat-plate absorber of solar energy, a transparent cover that allows solar energy to pass through but reduces heat losses, a heat-transport fluid (air, antifreeze or water) to remove heat from the absorber, and a heat insulating backing. The absorber consists of a thin absorber sheet (of thermally stable polymers, aluminum, steel or copper, to which a matte black or selective coating is applied) often backed by a grid or coil of fluid tubing placed in an insulated casing with a glass or polycarbonate cover. In water heat panels, fluid is usually circulated through tubing to transfer heat from the absorber to an insulated water tank. This may be achieved directly or through a heat exchanger. Most air heat fabricates and some water heat manufacturers have a completely flooded absorber consisting of two sheets of metal which the fluid passes between. Because the heat exchange area is greater they may be marginally more efficient than traditional absorbers.

Another type of collector is vacuum tube collector: it uses heat pipes for its core instead of passing liquid directly through it. Evacuated heat pipe tubes (EHPT's) are composed of multiple evacuated glass tubes each containing an absorber plate fused to a heat pipe. The heat from the hot end of the heat pipes is transferred to the transfer fluid (water or an antifreeze mix—typically propylene glycol) of a domestic hot water or hydronic space heating system in a heat exchanger called a "manifold". The manifold is wrapped in insulation and covered by a sheet metal or plastic case to protect it from the elements.

Source: http://en.wikipedia.org/wiki/Solar_thermal_collector

a chromatographic technique used to prepare samples for subsequent analysis, an effective method to concentrate or isolate the non-volatile analytes. It is a kind of column chromatography. The extract is eluted through the column (cartridge) containing the preconditioned sorbent by applying vacuum. The substance of interest is retained on the column and all the interfering components are eluted or the interfering components are retained and the substance of interest is eluted. This sample preparation technique is suitable for any compounds. The low solvent need, no need of concentration by evaporation and in this way avoiding the concentration of the polluting components, cheap sorbents, saving time, no emulsion formation, enhanced selectivity and potential for automatization are the advantages of SPE over the traditional liquid/liquid extraction (LLE).

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseoussolute, resulting in a solution.To distinguish between solutes and solvents, solvents are usually present in the greater amount.
The most common solvent in everyday life is water.
Commonly-used solvents are the organic solvents, which usually have low boiling point, can easily be removed by destillation or evaporation. solvents are usually clear and colorless liquids and many have a characteristic odor. 
Common uses for organic solvents are in dry cleaning (tetrachloroethylene), as paint thinners, as nail polish removers and glue solvents (acetone, methyl acetate, ethyl acetate), in spot removers (e.g. hexane, petrol-ether), etc. In 2005, the worldwide market for solvents had a total volume of around 17.9 million tons, which led to a turnover of about 8 billion Euro.

a noise caused by a shock wave (a propagating disturbance) that emanates from an aircraft or other object traveling at or above sonic velocity.

a physical technique employing ultrasound to intensely vibrate a sample media in extracting solvent and to maximise solvent/analyte interactions. Abbreviated as SAE, widely used for extracting the contaminants from soil.

sorption refers to the action of both absorption and adsorption taking place simultaneously. sorption means the incorporation of gases or liquids into a material of a different physical phase (gas into liquid, or liquid into solid) by adhering into the matrix or onto the surface.

In environmental transport processes we can hardly distinguish between absorption and adsorption, so that the use of the term sorption prevails.

diffusion into the environment of a sound emitted from a given source.

the introduction in the environment of noise deriving from various sources that can be grouped in: transportation activities, industrial activities and daily normal activities.