Soil, chemical analysis methods

Jackson, M. L. (1969). "Soil Chemical Analysis Advanced Course," 2nd edn. 7th printing, 1973. Department of Soil Science, University of Wisconsin, Madison, Wisconsin. Jackson, M. L. and G. D. Sherman (1953). Chemical weathering of minerals in soils. Adv. Agron. 5, 219-318. Jackson, M. L., S. Y. Lee, F. C. Ugolini, and P. A. Heimke (1976). Age and uranium content of soil micas from Antarctica by the fission track replica method. Soil Sci. 123, 241-248. 

A detailed review of the methods for deterrnination of low manganese concentration in water and waste is available (179). A review on the speciation of Mn in fresh waters has been reported (180). Reviews for the chemical analysis of Mn in seawater, soil and plants, and air are presented in References 181, 182, and 183, respectively. 

Soil geochemistry is widely applied in mineral exploration, and with advancing knowledge of speciation and residence phases of trace elements in soils, a variety of partial and selective extractions for chemical analysis have been developed over the past decades. Each of these methods has been designed to target and dissolve only those elements that are adsorbed onto labile phases in soil, from carrier fluids and gases that transported them from a deposit to the surface (e.g. Hall etal. 1996). 

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. 

Analytical procedures can be classified in two ways first, in terms of the goal of the analysis, and second, in terms of the nature of the method used. In terms of the goal of the analysis, classification can be based on whether the analysis is qualitative or quantitative. Qualitative analysis is identification. In other words, it is an analysis carried out to determine only the identity of a pure analyte, the identity of an analyte in a matrix, or the identity of several or all components of a mixture. Stated another way, it is an analysis to determine what a material is or what the components of a mixture are. Such an analysis does not report the amount of the substance. If a chemical analysis is carried out and it is reported that there is mercury present in the water in a lake and the quantity of the mercury is not reported, then the analysis was a qualitative analysis. Quantitative analysis, on the other hand, is the analysis of a material for how much of one or more components is present. Such an analysis is undertaken when the identity of the components is already known and when it is important to also know the quantities of these components. It is the determination of the quantities of one or more components present per some quantity of the matrix. For example, the analysis of the soil in your garden that reports the potassium level as 342 parts per million (ppm) would be classified as a quantitative analysis. The major emphasis of this text is on quantitative analysis, although some qualitative applications will be discussed for some techniques. See Workplace Scene 1.1. 

Schmid, O. (1984) Chemical soil analysis methods in biological husbandry. In Lampkin, N. and Woodward, L. (eds) The Soil Assessment, Analysis and Utilisation in Organic Agriculture. Elm Farm Research Centre, Practical Handbook Series, EFRC, Hamstead Marshall, UK, pp. 36M3. 

The factor analysis technique used was unable to distinguish separate soil and road sources. Ca appeared with Al, Si, K, Ti, and Fe on a factor that can be characterized only as "crustal," including both soil and road materials. It appears that a chemical element balance should always be used as a check on factor analysis results, at least until a more sophisticated factor analysis method, such as target transformation factor analysis (14), can be shown not to require it. 

In soil analysis, the sample pretreatment varies depending on whether a total elemental analysis or an exchangeable cation analysis is required. In the former, a silicate analysis method (see below) is appropriate. In the latter, the soil is shaken with an extractant solution, e.g. 1 M ammonium acetate, ammonium chloride or disodium EDTA. After filtration, the extractant solution is analysed. Fertilizers and crops can be treated as chemical and food samples, respectively. 

Subsequent experimental work in this laboratory was aimed at the systematic development of an efficient method for isolating the proteinaceous surfactants, which help stabilize natural microbubbles, from both commercial agarose powder and from forest soil samples collected locally. Successful isolation of this glycopeptide fraction was eventually achieved (ref. 322), and the results obtained from an extended program of chemical analysis, to further characterize and compare chemically these proteinaceous surfactants from both natural substances, are described below. 

A study by Rasemann et al. demonstrated to what extent mercury concentrations depend on the method of handling soil samples between sampling and chemical analysis for samples from a nonuniformly contaminated site [152], Sample pretreatment contributed substantially to the variance in results and was of the same order as the contribution from sample inhomogeneity. Welz et al. [153] and Baxter [154] have conducted speciation studies on mercury in soils. Lexa and Stulik [155] employed a gold film electrode modified by a film of tri-n-octylphosphinc oxide in a PVC matrix to determine mercury in soils. Concentrations of mercury as low as 0.02 ppm were determined. 

La Guardia and Garrigues [273] and Hall [274] have reviewed methods for the determination of metals in soil. Waymaugh [275] has reviewed the monitoring of historical changes in soil and atmospheric trace metal levels using dendro chemical analysis. 

In the practice of soil and sediment analysis, bioassays often are used in conjunction with chemical analysis and ecological field observations. This approach, named the TRIAD approach, was first introduced for sediment analysis by Chapman (1986) and is becoming more common for contaminated land assessment (Jensen and Mesman 2006). Such multimetric methods allow for reduction of uncertainties in risk assessment as evaluation is based on several independent lines of evidence (Chapman et al. 2002). 

In contrast, when sampling bulk material, the material cannot generally be viewed as a set of distinct units. For example, we sample liquids from tanks, drums, and pipelines, and particulate solids such as ore, powders, and soil. Individual units cannot be identified for sampling. Rather, we must decide on a sample mass Mg or volume the chemical sample size. Further, we must be concerned about whether to composite samples, and, if so, how much to include in each increment of the composite. An additionaJ complication is the restriction on the sample mass that must be used in a chemical analysis due to the method or instrumentation. In fact, a subsample is usually taken in the lab. 

For chemical analysis of each sample, approximately 10 g of soil was transferred to a Gooch crucible. Surface debris such as twigs were removed, and the crucibles were heated in a muffle furnace at 500 °C for 24 h to remove organic components. The ashed soil was then pulverized with a pestle in a porcelain mortar. For each soil position, four 0.5-g portions of fine powder were analyzed separately, and the results were averaged. Soil analyses were performed in-house by atomic absorption spectrometry on a Varian Model 1250 spectrophotometer according to our previously reported method, which involves total dissolution of the sample in acid (11,12). The elements assayed were strontium, zinc, magnesium, calcium, sodium, lead, iron, aluminum, manganese, and potassium. 

After transport to a laboratory, gases are introduced into an analytical instrument for quantitative determination of the constituents of interest. Soil air in a container is introduced directly to the instmment, whilst adsorbed gas is released by thermal of chemical desorption. The instrumental methods most widely used for gas analyses include gas chromatography, mass spectrometry and atomic absorption spectrophotometry. For quantifying the radiation scars on film, image analysis methods are employed. 

W. Rasemann, U. Seltmann, and M. Hempel, Statistical Evaluation of the Influence of Several Sample Pretreatment Methods on the Mercury Content Detectable by Chemical-analysis of Contaminated Soil Samples Under Practical Conditions, Presenius J. Anal. Chem. 351(7), 632-641, Apr. (1995). 

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