Selective chemical extraction

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,... 

Adsorption to mineral surfaces such as Fe and Al (hydr)oxides has long been known to be an important process that limits the mobility of heavy metals and metalloid species in aqueous systems (e.g., Stumm 1992). The sorption of ionic species in MSWI bottom ash has been recently studied in detail by Meima Comans (1998, 1999). These authors used a sequence of selective chemical extractions to determine sorbent concentration, namely Fe and Al (hydr)oxides. Their model calculations suggested that Zn(II) and M0O4 sorbed to Fe (hydr)oxides, while Pb(II) and Cu(II) appeared to have a greater affinity for Fe (hydr)oxides. The sorption of Cd(Il) was found to be very weak. The interpretation of... 

After both sets of experiments were completed, the ground-water was drained from the cells and selective chemical extractions of the granite cell walls were performed. The cells were filled with 0.5 mol/L CaCl solution and stirred continuously for 72 h to displace exchangeable radionuclides. After a rinse with demineralized water to remove residual CaCl- solution, the cells were filled with KTOX solution and stirred ror 24 h to remove radionuclides associated with oxyhydroxides. All solutions were analyzed by gamma spectrometry to determine the amounts of radionuclides extracted. Residual activity was measured by direct gamma counting of the cells. 

Selective Chemical Extraction, minerals, the interpretation of selective extraction data requires knowledge of the sorptive capacity of those minerals and their susceptibility to alteration during the course of experiments ... 

TABLE VI. Comparison of Model Predictions and Selective Chemical Extraction Data... 

Assuming, in Table III, that represents exchangeable activity and S2 represents the net inventory of all other mechanisms, a comparison of these model-predicted inventories with those obtained by selective chemical extraction indicates that, while the overall mass balance trends are predicted, agreement in detail of individual extraction inventories with the model-predicted inventories is not always good. The overall mass balance is governed almost totally bv the higher concentration (early time) data. In the case of °Co, inspection of residual plots indicates that, in all cases, the DFO model shows small systematic deviations at early times that account for the mass... 

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. 

Sequential extraction experiments have been shown to provide a convenient means to determine the metals associated with the principal accumulative phases in sedimentary deposits, to elucidate the mechanisms of their diagenetic transformation, and to elucidate release processes upon changing environmental conditions (Kersten and Forstner, 1989). A general goal of all studies involving selective chemical extraction is the accurate determination of partitioning of elements of environmental concern among different discrete phases of a sample. 

Tipping, E., Hetherington, N.B., Hilton, J., Thompson, D.W., Bowles, E. and Hamilton-Taylor, J. (1985) Artifacts in the use of selective chemical extraction to determine distributions of metals between oxides of maganese and iron. Anal. Chem., 57,1944—1946. 

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). 

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