Speciation for Soils and Sediments

Speciation of metal content in solids can be accomplished during the extraction process by subjecting the sample to successive extractions with progressively more aggressive solvents, or by extracting different subportions of sample with the different solvents. It has been shown that it is more difficult to obtain comparable results when using sequential extractions rather than individual extractions of subsamples with different extractants [124]. Some applications of extractions with different solvents are extraction with  

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 

The availability of the analytes for uptake by plants, for transport through the soil, and for dissolution into water can be estimated from a well-studied speciation scheme. Risk assessment for disposal of wastes in landfills or for land disposal of dredge spoils or sewage sludges requires knowledge not only of the total metal content but also of the content in each separate fraction to begin to understand how the metals will act in the environment. Table 5.7 summarizes the methods available for speciation of metals in samples. 

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