Sequential leaching technique

Rapin, F. and Forstner, U. (1983) Sequential leaching techniques for particulate metal speciation the selectivity of various extractants. In Proceedings of the 4th International Conference on Heavy Metals in the Environment, Vol. 2, Heidelberg, CEP Consultants, Edinburgh, pp. 1074-1077. 

Understanding sulfate transport and retention dynamics in forest soils is a prerequisite in predicting S04 concentration in the soil solution and in lake and stream waters. In this study, forest soil samples from the Gardsjon catchments, Sweden, were used to study S04 transport in soil columns from the upper three soil horizons (E, Bs, and BC). The columns were leached using a sequential leaching technique. The input solutions were CaS04 equilibrated with forest floor material. Leaching behavior of S04 and concentration in the effluent were measured from columns from individual horizons. S04 was always retained in the Bs and BC horizons, while... 

Simultaneous application of standard sequential leaching techniques can be used for geochemical characterization of anoxic, sulfide-bearing sediments in relation to the potential mobility of critical trace metals (Kersten and Fbrstner 1991). 

The geochemical behaviour of Cs and Pu in Solway floodplain cores, collected from Southwick Water, south-west Scotland, has been studied by Allan et al. (1991) by employing a sequential leaching scheme (Cook et al., 1984 Livens Baxter, 1988b McDonald et al., 1990). This scheme incorporates solutions of calcium chloride (readily available sites), acetic acid (specific adsorption sites), tetra-sodium pyrophosphate (organically associated), ammonium oxalate/oxalic acid, (Fe and Mn secondary minerals), dilute nitric acid (dilute acid soluble sites) and nitric acid/ hydrofluoric acid (residual fraction). This technique has been subject to... 

The term species generally refers to the molecular forms of an element or a cluster of atoms of different elements in a given (in this case solid) matrix (Bernhard et al., 1986a). The term form is also used to indicate uncertainty or lack of knowledge about the exact nature of the species one expects to find in an environmental sample. Conditional speciation assessment techniques like sequential extractions or leaching tests are not able to yield information at the true molecular level in solid phases thus the more general term form is used rather than species when referring to the results of such techniques commonly applied to date to soils and sediments. 

As an example of such an integrated approach, a case study is reported in which a soil from a former smelter and scrapyard was investigated. The case study demonstrates the importance of an investigative approach that employs a range of analytical techniques to evaluate toxic metal distribution and mobility. It showed that total element analyses of separated size fractions, characterization leaching tests such as sequential extractions, and detailed electron microscope analysis can provide complementary information on the location and chemistry of toxic metals in soils. 

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