Soil, chemical analysis mineralogy

Chemical elements that are either present naturally in the soil or introduced by pollution are more usefully estimated in terms of availability of the element, because this property can be related to mobility and uptake by plants. A good estimation of availability can be achieved by measuring the concentration of the element in soil pore water. Recent achievements in analytical techniques allowed to expand the range of interest to trace elements, which play a crucial role both in contaminated and uncontaminated soils and include those defined as potentially toxic elements (PTE) in environmental studies. A complete chemical analysis of soil pore water represents a powerful diagnostic tool for the interpretation of many soil chemical phenomena relating to soil fertility, mineralogy and environmental fate. This chapter describes some of the current methodologies... 

The density of the soil particle is another factor which affects the accuracy of Stoke s law. Density depend upon the mineralogical and chemical constitution of the particles as well as upon their degrees of hydration. Usually p is taken to be 2.65 and a, 1.00 for mechanical analysis. 

By convention, soil samples used in the analysis have to be air-dried, crushed, and sieved to 2 mm. By convention, chemical, physical, and mineralogical analysis are made on the <2 mm material. Therefore, SOM includes only those organic materials that accompany soil particles through a 2 mm sieve. 

In general, however, one would recommend that differential thermal analysis be used along with other more determinative methods such as X-ray diffraction. It can then give valuable information, which cannot be obtained by any other technique. Indeed, for a complete mineralogical analysis of a soil clay, it would be unrealistic to rely on any one determinative method, as none can give complete information. Instrumental (X-ray diffraction, thermal methods, infrared absorption spectroscopy, and electron microscopy and diffraction) and chemical (selective dissolution, cation exchange, and total analysis) methods all contribute some information, and only by application of all available can an accurate assessment be made. 

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