Speciation in Soils and Sediments

Rubio, R. and Ure, A.M. (1993) Approaches to sampling and pretreatment for metal speciation in soils and sediments. Int.f. Environ. Anal. Chem., 51, 205-217. 

Ure, A.M., Davidson, C.M. and Thomas, R.P. (1995) Single and sequential extraction schemes for trace metal speciation in soil and sediment. Tech. Instr. Anal. Chem., 17, 505-523. 

A variety of methods have been used to characterize the solubility-limiting radionuclide solids and the nature of sorbed species at the solid/water interface in experimental studies. Electron microscopy and standard X-ray diffraction techniques can be used to identify some of the solids from precipitation experiments. X-ray absorption spectroscopy (XAS) can be used to obtain structural information on solids and is particularly useful for investigating noncrystalline and polymeric actinide compounds that cannot be characterized by X-ray diffraction analysis (Silva and Nitsche, 1995). X-ray absorption near edge spectroscopy (XANES) can provide information about the oxidation state and local structure of actinides in solution, solids, or at the solution/ solid interface. For example, Bertsch et al. (1994) used this technique to investigate uranium speciation in soils and sediments at uranium processing facilities. Many of the surface spectroscopic techniques have been reviewed recently by Bertsch and Hunter (2001) and Brown et al. (1999). Specihc recent applications of the spectroscopic techniques to radionuclides are described by Runde et al. (2002b). Rai and co-workers have carried out a number of experimental studies of the solubility and speciation of plutonium, neptunium, americium, and uranium that illustrate combinations of various solution and spectroscopic techniques (Rai et al, 1980, 1997, 1998 Felmy et al, 1989, 1990 Xia et al., 2001). 

Hirner AV (1992) Trace element speciation in soils and sediments using sequential chemical extractions methods. Int J Environ Anal Chem, 46 77-85 Hirner AV, Forstner U (1993) Elutionstests zur Bestimmung der Schadstoffmobilitat. 

In the atmosphere, cadmium is present as a result of both namral and man-made activities, mainly in finer particles. It mainly occurs in various inorganic forms, though organic complexation may play important roles in some cases. In the natural waters, cadmium is mainly present as chloride and/or carbonate species, though the presence of organic ligands may influence its speciation. In soils and sediments, including soil solutions, cadmium speciation is deeply affected by the characteristic of the matrix. 

Carbonates, organic matter, Fe and Mn oxides, and clay minerals play important roles in controlling overall reactivity of trace elements in soils and sediments. This chapter addresses the interaction of trace elements with carbonates, organic matter, Fe and Mn oxides and clay minerals. Analytical techniques for trace element speciation in solid-phase and their distribution among various solid-phase components in arid and semi-arid soils are reviewed. Solubilities of trace elements in solid phases and their mineralogical characteristics in arid and semi-arid soils also are discussed. 

Lobinski et al. [72] optimized conditions for the comprehensive speciation of organotin compounds in soils and sediments. They used capillary gas chromatography coupled to helium microwave induced plasma emission spectrometry to determine mono-, di-, tri- and some tetraalkylated tin compounds. Ionic organotin compounds were extracted with pentane from the sample as the organotin-diethyldithiocarbamate complexes then converted to their pentabromo derivatives prior to gas chromatography. The absolute detection limit was 0.5pg as tin equivalent to 10-30pg kg-1. 

Bertsch, P. M., Hunter, D. B., Sutton, S. R., Bajt, S. Rivers, M. L. 1994. In situ chemical speciation of uranium in soils and sediments by micro x-ray absorption spectroscopy. Environmental Science and Technology, 28, 980-984. 

Species distribution studies have shown that trace element (e.g. metals) concentrations in soils and sediments vary with physical location (e.g. depth below bed surface) and with particle size. In these speciation studies the total element content of each fraction was determined using a suitable trace element procedure, for example, solid sample analysis by X-ray emission spectroscopy or neutron activation analysis, or alternatively by dissolution of sample and analysis by ICPOES, AAS or ASV. The type of sample fraction analysed can vary, and a few... 

The analysis of samples extracted with various solvents will provide information on the most easily removed metal species, the less available, and the most refractory metal content, which is dissolved only by the strongest acid extractants. There are at least a dozen different published speciation schemes for metals in soils and sediments. Many are based on the pioneering work by Tessier et al. [125]. Most include releasing metals from carbonates and hydrous oxides with acids, and an oxidation step to destroy organic... 

Bioavailability of metals in soil and sediments is a topic that requires strengthening from a scientific point of view. Chemical speciation models for metals in soil and sediment are in the process of being developed. Media- and matrix-related differences in intrinsic sensitivity of species comprise a topic that deserves to be studied. 

Ure, A., Quevauviller, H., Muntau, H., and Griepink, B. (1993b). Speciation of heavy metals in soils and sediments. An account of the improvement and harmonization of extraction techniques undertaken under the auspices of the BCR of the CEC. Int.J. Environ. Anal. Chem. 51, 135-151. 

Tack, F. M. G., and Verloo, M. G. (1995). Chemical speciation and fractionation in soil and sediment heavy metal analysis A review. Int.J. Environ. Anal. Chem. 59(2—4), 225. 

In soils and sediments, the speciation in the dissolved aqueous phase is primarily important to assess bioavailability and toxicity. The total concentration (adsorbed and solid phase) gives an idea of the capacity of a reactive element, which could under certain circumstances (e.g., acidification, complex formation) be mobilized. 

The degree to which a pollutant is taken up, which also determines its potential toxicity, is determined by its bioavailability. Bioavailability refers to the ability of a chemical to move from the environment into a living organism. Bioavailability depends upon the ionization state and speciation of a chemical. Because certain organic compounds and clays can strongly bind various hydrocarbon chemicals and metals, the amount of organic carbon and clay in the soil, sediment, and water determines the bioavailability of these compounds. Bioavailability of metals is also dependent on the amount of sulfur precipitates of other metals in soils and sediments. 

Manceau, A., Marcus, M. A., and Tamura, N. (2002). Quantitative speciation of heavy metals in soils and sediments by synchrotron x-ray techniques. In Applications of Synchrotron Radiation in Low-Temperature Geochemistry and Environmental Science, Vol, 49, ed. Fenter, P., and Sturchio, N. C., Mineralogical Society of America, Washington, DC, 341-428. 

Han, Y, Kingston, H. M., Boylan, H. M., Rahman, G. M., Shah, S., et al. Speciation of mercury in soil and sediment by selective solvent and acid extraction. Anal Bioanal Chem 2003,375,428M36. 

The principal abiotic processes that transform strontium in soils and sediments are mediated by sorption and desorption reactions between the soil solution and matrix (precipitation, complexation, and ion exchange), and controlled by pH, ionic strength, solution speciation, mineral composition, organic matter, biological organisms, and temperature (see Section 6.3.1). 

Maes, A. Cremers, A. (1986) Radionuclide sorption in soils and sediments Oxide-organic matter competition. In Speciation of Fission and Activation Products in the Environment, eds. R.A. Bulman J.R. Cooper, pp. 93-100. London Elsevier Applied Science Publ. 

Liu, Y., Lopez-Avila, V., Alcaraz, M., and Beckert, W. F., Offline complexation/SFE and GC with atomic emission detection for the determination and speciation of organotin compounds in soils and sediments. Anal. Chem., 66, 3788-3796, 1994. 

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