Significance for soil properties

redoximorphic Gleys, Pseudogleys Massive ferricretes, Bog iron ores Lake ores 0.1 

As before but non-redoximorphic moderately acid Alfisols, Inceptisols 0.07-0.15 

Except for the top soil where the colour caused by Fe oxides is often masked by hu-mics, most of the soil profile receives its brown, yellow or red colour from Fe oxides (Bigham Ciolkosz, 1993). Because this is so obvious to the naked eye, soils have been named according to colour in most national classification systems, e. g. red-yellow podzols (USA), sol ochreux (France), Braunerde (Germany), krasnozem (Russia), terra rossa (Italy), and even the current modern international systems (U.S. Soil Taxonomy system and World Reference Base for Soil Resources, WRB) use colour connotations such as Rhodic (red) and Xanthic (yellow). 

This reflects the fact that the colour is one of the easiest ways of distinguishing soils. Even in 1937 Alexander et al. noticed that very red soils owe their colour to the presence of hematite . An objective notation of soil colour is needed to describe 

5 YR to 10 R as the hematite/goethite ratio increased from 0 to 1 (Fig. 16.11), whereas hues of soils containing only goethite ranged between 7.5 YR and 2.5 Y. Soils with lepidocrocite and ferrihydrite covered the in-between-range of 5 YR- 

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The modern procedure to minimise corrosion losses on underground structures is to use protective coatings between the metal and soil and to apply cathodic protection to the metal structure (see Chapter 11). In this situation, soils influence the operation in a somewhat different manner than is the case with unprotected bare metal. A soil with moderately high salts content (low resistivity) is desirable for the location of the anodes. If the impressed potential is from a sacrificial metal, the effective potential and current available will depend upon soil properties such as pH, soluble salts and moisture present. When rectifiers are used as the source of the cathodic potential, soils of low electrical resistance are desirable for the location of the anode beds. A protective coating free from holidays and of uniformly high insulation value causes the electrical conducting properties of the soil to become of less significance in relation to corrosion rates (Section 15.8). 

The lead contents of 206 soil samples determined by AAS indicated that such determination provides a useful parameter for soil comparison and discrimination in forensic science (Chaperlin 1981). Soil investigations near a former smelter in Colorado revealed that historic use of arsenical pesticides has contributed significantly to anthropogenic background concentrations of arsenic on certain residential properties. A variety of forensic techniques including spatial analysis, arsenic speciation and calculation of metal ratios were successful in the separation of smelter impacts from pesticide impacts (Folkes, Kuehster, and Litle 2001). 

Diatomaceous earth is composed of the siliceous skeletons of microorganisms. It is pozzolanic, but its use in concrete is much restricted by its very high specific surface area, which greatly increases the water demand. Some clays react significantly with lime at ordinary temperatures, but while this property can be of value for soil stabilization, their physical properties preclude their use in concrete. Many clay minerals yield poorly crystalline or anrorphous decomposition products at 600-900 C (Section. 3.3.2), and if the conditions of heat treatment are properly chosen, these have enhanced pozzolanic properties. Heat-treated clays, including crushed bricks or tiles, can thus be used as pozzolanas in India, they are called surkhi. Other examples of natural rocks that have been used as pozzolanas, usually after heat treatment, include gaize (a siliceous rock containing clay minerals found in France) and moler (an impure diatomaceous earth from Denmark). The heat-treated materials are called artificial pozzolanas, and this term is sometimes used more widely, to include pfa. 

In this section, we will consider the effects of soil texture and soil nutrient status on decomposition. The initial stages of leaf litter decomposition will be at least partially decoupled from control by edaphic properties of the soil environment. For example, Scott et al. (1996) found that while SOM decomposition varies significantly with soil texture, the CO2 evolution from surface litter does not. However, as partially decomposed litter is incorporated into the soil both through abiotic and biotic means, the physical characteristics of the soil begin to play an important role in the overall degradation and stabilization of the organic inputs. 

Iron oxides are widespread in nature. They are ubiquitous in soils and roeks, lakes and rivers, on the sea floor, in air (e.g. admixed in aeolian Sahara dust) and in organisms, and they may be responsible for the red-dish-eolored surface of the Mars. Iron oxides are of great significance for many of the properties and processes taking place in ecosystems. 

After each soil sample was blended, air dried, and screened (2 mm sieve opening) triplicate aliquots were taken and analyzed for 2,3,7,8-TCDD, CDD and CDF congeners, and 2,4-D and 2,4,5-T. The three prepared soils had 2,3,7,8-TCDD levels greater than 100 ng/g and 2,4-D/2,4,5-T levels of about 1000 yg/g. The JI soil had significant concentrations of hepta and octa CDD compared with the other two samples. In addition, selected physical and chemical properties presented in Table I, were measured (6). The EPA test program (5) had indicated that soil properties had only a minor influence on removal efficiencies for 2,3,7,8-TCDD. 

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