Soils, analysis types

For studies involving test substance application to soil, there may be a requirement for more soil information than for studies where applications are made to foliage of established crops. The study protocol should describe any specific requirements relative to soil type selection and how to confirm the soil characteristics for the study. Most studies simply require that the soil be identified by its name (e.g., Keystone silt loam) and composition (e.g., percent sand, silt, and clay). This information can typically be acquired from farm records, a soil survey of the local area, or a typical soil analysis by a local soil analysis laboratory. In some instances, a GLP compliant soil analysis must be completed. The study protocol must clearly define what is needed and how it is to be obtained. Unless specified in the protocol, non-GLP sources are adequate to identify the soil and its characteristics. The source of the soil information should be identified in the field trial record. 

Information about the soil in its natural state is thus an essential part of any soil sampling. This information may be available from previous soil analysis, that is, before contamination took place. This type of information is commonly available from the state s land grant university and the areas soil survey. Another option would be to obtain historical soil samples. Historical soil samples are samples of the soil taken before contamination has occurred and thus can be used to ascertain the natural levels of components of interest in that soil. These contain information that may not be readily available otherwise. Caution must be used because storage of soil samples can change analyte composition including the most prominent species present (see Table 7.1 and Reference 2). 

Both direct and indirect methods are used in studying soil chemistry. While in all cases direct methods are preferable, it is not always possible to make direct observations of all the chemical species, and physical and chemical changes of interest. Thus, it is often necessary to modify the soil before analysis. In many cases, it is essential to extract components before analysis can be carried out. It is also possible to obtain valuable information about the chemistry of soil by carrying out analyses that destroy all or a part of the soil matrix. A summary of analysis types and instruments commonly used in soil analysis is given in Table 8.1. 

TABLE 8.1. Summary of Analysis Types and Instrumentation Used in Soil Analysis... 

Numerous types of electrodes are used for soil analysis. Simple elemental electrodes such as platinum, mercury, and carbon are the most frequently used, while other unreactive metals such as gold and silver and the more reactive copper and zinc and others have also been used. Both stirred and unstirred solutions and suspensions are used during analysis. In some cases, electrodes are rotated or, in the case of mercury, dropped into the solution being analyzed. 

Titration is a general word used in many different disciplines. Any time a solution of known concentration is used to find the amount of an unknown component in another solution, it can be called a titration. Although this type of analysis is very old, it still finds widespread used in chemical analysis. Titrations are used in soil analysis to measure soil acidity, soil organic matter content, and various constituents isolated from soil, particularly ammonia. 

In both types of extraction, it is not certain that all the water or even a representative sample of the water is removed from soil. Water in small pores, cracks, or held at greater pressures that those applied to remove water will not be removed and their constituents will not be included in the analysis. However, both these methods find wide use in soil analysis. 

Although such instruments as described earlier are available, they are not typically used in soil analysis. Today, samples are most often aspirated into a flame or torch to cause the promotion of electrons in elements, and the diagnostic wavelengths are detected and quantified by photomultipliers. Modern spectrometers are different because of the use of many different ways of heating samples and the range of wavelengths available. Today, because of increased sensitivity of instrumentation and detectors, more of the spectrum is available for this type of analysis. Thus, wavelengths from 200 to 900 nm can be used for the analysis of the elements that are present. 

As regards a contaminated soil, this type of analysis may not be possible because the various hydrocarbons cannot be extracted from the sample with equal efficiency. Volatile organic compounds require special procedures to achieve satisfactory recovery from the soil matrix. It thus becomes important to distinguish between those compounds that are considered to be volatile and those that rank as semi- or nonvolatile compounds. 

The use of a direct combined (or polyphasic) approach can create highly specific soil fingerprints from normal constituents. This, in addition to the application of appropriate statistical analysis, would make soil analysis a more effective tool for routine forensic work, thus considerably extending its applicability. Indeed, combinations of different data each with its own discriminatory potential may result in probabilities of association or disassociation that even surpass those of techniques such as human DNA. Initial work using a canonical variate analysis has shown discrimination between soil types can be improved by including more analytical data. Figure 11.11 illustrates... 

Procedure for special type of mechanical and mineralogical soil analysis. Proc. Soil Sci. Soc. America, 1 101-112. 

The samples must be stored in good conditions pending analysis. The storage conditions that are appropriate will depend upon the type of sample and the determinations required. Most soil analysis, for example, is done on air-dried soil, but the nitrate content can be altered by drying, so nitrate studies are usually done on fresh soil. If the soil has to be stored, this should be at <4 °C and for no more than 48 hours. Similarly samples in which analysis of the volatile components is required, such as silage, urine and faeces, are usually kept frozen until immediately before the analysis. 

Ringrose-Voase, A.J., and P. Bullock. 1984. The automatic recognition and measurement of soil pore types by image analysis and computer programs. J. Soil Sci. 35 673-684. 

This book attempts to cover chemical and ecotoxicological analysis related to routine contaminated land investigations. It does not cover analysis related to research or specialist one-off project type investigations. The following chapter deals with soil analysis method requirements, how methods should be validated and the need for all methods to meet clearly defined performance requirements. It also covers quality assurance/quality control aspects. Chapter 3 covers the key, and problematic area of sample homogenisation and the initial sample preparation. Chapter 4 covers the analysis of metals and elemental... 

Soil analysis is usually aimed at evaluating its agricultural characteristics. The soil chemical composition is very diverse and the definition of pollutants in soil, natural as well as anthropogenic, depends on the soil type, locality and also on the composition assumed to be normal . The comparison with assumed normal levels of particular components is achieved by using standard samples of soils, or of similar soils from a different region. Standard soil samples are not commonly available and thus, the second... 

Site-specific geotechnical investigation and dynamic site response analysis shall be performed to determine seismic coefficients lor Soil Profile Type Sf-... 

When phenolic acids enter the soil environment they are reversibly and irreversibly sorbed to soil particles, polymerized, oxidized, reduced, leached, utilized by microbes, and taken up by roots. Rates for these various processes are highly variable and depend on soil type, biotic and physicochemical soil environmenL types and mixtures of phenohc acids in or added to soils, and time, among others. To eliminate the effects of soil microbes, soils may be autoclaved. Concentrations of individual available phenolic acids in soils at a given point in time may be estimated by extracting soils with appropriate extractants and HPLC analysis. Based on our soils, we recommend water for estimating soil solution concentrations and neutral EDTA for soil solution and reversibly sorbed phenolic acid concentrations. However, the effectiveness of neutral EDTA in recovering available phenolic acids in all other soils should not be assumed. Reversibly sorbed phenolic acids increased or decreased as soil solution concentrations and multivalent cations increased or decreased, respectively. 

A decision has to be made as to how much and what type of fertilisers should be used for eaeh crop. For phosphoms, potassium and magnesium the amourrt applied should be based on an analysis of a soil sample. Soil analysis will show ... 

An integrated approach needed. Where soil analysis indicates, grow resistant varieties. There are many varieties that are resistant to the golden nematode but ordy a few varieties that show partial resistance to the wMte nematode. Wide rotations help keep populations low. Plant classified seed. The effectiveness of nematicides depends on nematode populations and type of product. The use of trap cropping is being investigated. 

The development of methods of analysis of tria2ines and thek hydroxy metabohtes in humic soil samples with combined chromatographic and ms techniques has been described (78). A two-way approach was used for separating interfering humic substances and for performing stmctural elucidation of the herbicide traces. Humic samples were extracted by supercritical fluid extraction and analy2ed by both hplc/particle beam ms and a new ms/ms method. The new ms /ms unit was of the tandem sector field-time-of-flight/ms type. 

There are numerous examples of successful application of the developed procedures using native and immobilized enzymes in analysis of environmental (waters and soils of different types, air) and biological (blood semm, urine) samples. 

Soil extracts are usually very complex. In water samples, humic and fulvic acids make analysis difficult, especially when polar substances are to be determined. Multidimensional chromatography can also make a significant contribution here to this type of analysis. 

However, in most cases the AW(D) dependencies are distinctly nonlinear (Fig. 9), which gives impulse to further speculations. Clearly, dependencies of this type can result only from mutual suppression of the hydrogel particles because of their nonuniform distribution over the pores as well as from the presence of a distribution with respect to pore size which does not coincide with the size distribution of the SAH swollen particles. A considerable loss in swelling followed from the W(D) dependencies, as shown in Fig. 9, need a serious analysis which most probably would lead to the necessity of correlating the hydrogel particle sizes with those of the soil pores as well as choice of the technique of the SAH mixing with the soil. Attempts to create the appropriate mathematical model have failed, for they do not give adequate results. 

As part of a study of the secondary chemistry of members of Cistus (the rock-rose) in France, Robles and Garzino (1998) examined the essential oil of C albidus L. Plants were sampled from two areas in Provence characterized by different soil types, calcareous sites west of Marseille, and siliceous sites near Pierrefeu-du-Var and Bormes les Mimosas (PF and BM, respectively, in Fig. 2.23), which lie about 60 km and 80 km to the east, respectively, in the Massif les Maures. Regardless of the soil type, a-zingiberene [88] (Fig. 2.24) was the dominant component. Concentrations of other major components of the plants varied between the two soil types, as summarized in Table 2.6. Many other compounds were present in lesser amounts, but varied little between the two areas. A more recent paper by the same workers (Robles and Garzino, 2000) described an analysis of C. monspeliensis L. leaf oils, the results of which are summarized in Table 2.7. 

Mineral exploration, the search for economic ore deposits, requires somewhat different reference samples than those used in ore valuation. Soil or sediment and water samples are frequently used in the search when mineralized areas of abundant outcrop or those covered only by thin locally derived overburden are being evaluated. In such cases, it is virtually impossible not to detect the mineralization from an analysis of ore elements in these types of samples. Later, as the mineral deposits closest to the surface were exploited and then played out, new deposits occurred at progressively greater depths, and these sample types were less and less effective as markers in the search (Hoffman 1989). 

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