Selective chemical extraction soils

Kelsey JW, Kottler BD, Alexander M (1997) Selective chemical extractants to predict bioavailability of soil-aged organic chemicals. Environ Sci Technol 21 214-217... 

Ure AM, Davidson CM. Chemical speciation in soils and related materials by selective chemical extraction. In Ure AM, Davidson CM (eds.), Chemical Speciation in the Environment, 2nd ed. Malden, MA Wiley-Blackwell Science, Inc. 2002, pp. 265-299. 

To study the chemical speciation of Aluminum in the solid - phase of the selected soil samples by selective chemical extraction procedures,... 

Part II considers speciation in specific compartments of the environment viz. the atmosphere, biological systems, soils, sediments and natural waters, and with particular aspects of the speciation of environmentally important radionuclides. Two new chapters have been added to make the coverage even more comprehensive. These new chapters are Chapter 10, Chemical Speciation in Soib and Related Materials by Selective Chemical Extraction by the editors, and Chapter 12, Speciation in Seawater by R.H. Byrne of the University of South Florida. 

With solid samples (e.g. suspended particles, sediments and soils), determination of the species distribution pattern usually involves a series of selective chemical extraction steps, but it is now recognised that many experimental parameters can influence the amount extracted by the reagents, and there are many potential sources of error. For example, during an extraction step, metal ions released from one phase can resorb on other exposed surfaces and, where coatings are being removed in the process, the values obtained can be influenced by the order in which reagents are used. 

Pickering, W.F. (1981) Selective chemical extraction of soil components and bound metal species. CRC Crit. Rev. Anal. Chem., 12, 233-266. 

Chemical speciation in soils and related materials by selective chemical extraction... 

This chapter considers methods of trace element speciation, and their application to soils, that involve selective chemical extraction techniques. It will be concerned firstly with extraction by single selective reagents and secondly with the development and application of sequential extraction procedures for soils and related materials. Sequential extraction procedures for sediments are discussed in depth in Chapter 11. Speciation in the soil solution and modelling aspects of its interaction with soil solid phases are comprehensively covered in Chapter 9 and will not be considered here. 

More widely applied to determine the potential, plant and human bioavailability are the methods of PTMs speciation which involve selective chemical extraction techniques. Estimation of the plant- or human-available element content of soil using single chemical extractants is an example of functionally defined speciation, in which the function is plant or human availability. In operationally defined speciation, single extractants are classified according to their ability to release elements from specific soil phases. Selective sequential extraction procedures are examples of operational speciation (Ure and Davidson, 2002). 

Extraction procedures for plant uptake studies have existed for many years. These species are defined by their function, e.g. plant-available forms. The species defined in this way, however, are unlikely to be distinct chemical forms but may include a range of chemical entities that share the same function, e.g. are all available to plants. This type of functionality, using selective chemical extractants, has been widely employed in soil and agricultural laboratories to diagnose or predict toxicity deficiencies in crops and in animals eating such crops. Table 5.7 illustrates the diversity of this type of selective extraction. It is noted that the methods, evolved over many years on an empirical basis, are both element-specific and crop-specific. 

The differences in Zn(II)-containing phase association determined by Juillot et al. (2002) vs. Manceau et al. (2000a) in smelter-contaminated soils show that in complex phase assemblages, EXAFS data alone may not be sufficient to uniquely identify the types of phases with which a contaminant is associated. In these cases, other complementary methods, such as selective chemical extraction and , are needed, and even then it may not be possible to uniquely identify all the phases that contain the contaminant element or to resolve differences in interpretation. 

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