Sequential leaching

Regolith samples were collected from 68 sites along a transect extending from the CTSS in the SW of the island (near napa tou Pcjpiou), across Troodos and into the CTSS and fanglomates on the NE side of Troodos (near AsuKioaia). ICP-MS trace elements concentrations were determined following two conventional (sequential) leaches on the <2mm fraction of the upper (0-25 cm) and lower (50-75 cm) parts of the profile 1M ammonium acetate in pH 5 acetic acid and 1M hydroxylamine.HCI in pH 1 HCI. 

Huggins, F.E., Huffman, G.P., Kolker, A. et al. (2002) Combined application of XAFS spectroscopy and sequential leaching for determination of arsenic speciation in coal. Energy and Fuels, 16(5), 1167-172. 

After drying and sieving the fine-grained fraction (particle diameter <63 pm) was split. One part was sequentially leached according to TESSIER [TESSIER et al., 1979] to give the following fractions ... 

By applying methods of sequential leaching, direct chemical information can be obtained and a rough assessment of the remobilization potential of the sedimented heavy metals is possible. Because of the lack of specifity of the extraction procedures particular species cannot be identified (see also critical hints in [KHEBOIAN and BAUER,... 

Figure 7.2 Solid-state speciation in a crustal aerosol collected close to the Saharan Desert and an urban aerosol collected in the UK (Spokes et al., 1994). Results are expressed as a percentage of the total elemental concentration and obtained using a three stage sequential leach using the method of Chester et al. (1989). Stage one uses 1.0 M ammonium acetate to release loosely bound metals. Stage two involves addition of 1.0M hydroxylamine hydrochloride in 25% acetic acid to the residue to release metals held within the oxide and carbonate phases. Stage three uses nitric acid and hydrofluoric acid to break down the aluminosilicate lattice and release metals associated with the crustal fraction of the aerosol.

Chester, R., Lin, F.J. and Murphy, K.J.T. (1989) A three stage sequential leaching scheme for the characterisation of the sources and environmental mobility of trace metals in the marine aerosol. Environ. Technol. Letts, 10, 887-900. 

Cave, M.R. and Wragg, J. (1997) Measurement of trace element distributions in soils and sediments using sequential leach data and a non-specific extraction system with chemo-metric data processing. Analyst, 122, 1211-1221. 

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. 

In the case of solid environmental materials such as soils, sediments or indeed suspended particulates the use of selective chemical leaching methods can provide some basic information regarding the nature of the radionuclide species bound to the solid matrix. A typical sequential leaching might follow a procedure similar to that suggested for the study of trace metal binding to sediments by Gupta and Chen (1975) as shown in Fig. 13.2. 

The results of sequential leaching experiments and the bioaccumulation studies reveal a selective assimilation of certain chemical forms of some trace metals by molluscs. There seems to be a relationship between seawater-soluble chromium levels and accumulation of the element in the kidneys of exposed bivalves. Particulate forms of chromium, while present in the digestive glands, do not appear to have been assimilated by the organisms, even though much of the total chromium was dissolved by a relatively mild extractant -25% acetic acid. Thus, an estimation of the bioavailability of particulate metals based on their solubility in dilute acetic acid can be erroneously high, at least for herbivorous filter feeders. 

FIGURE 12.2 A schematic of the sequential leaching experiment through 5-cm soil columns from the E, Bs, and BC horizons (FF = forest floor). 

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... 

The sediment samples were sequentially leached in accordance with the method of Tessier et al. (1979) in which five fractions are experimentally defined. The extracts were analysed by atomic absorption (Perkin Elmer 3030), (Pb and Rb), and inductively coupled plasma spectrometry (ARL 35000), (Cu, Zn, Cd, Ni, Fe and Mn). Instrumental precision was better than 1 % and accuracy was ensured by analysing a range of international reference sediments. 

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... 

Table 8.7 Sequential leaching from Southwick Water floodplain (°/o distribution) (Allan etal., 1991)...

Koschinsky, A. and Halbach, P., Sequential leaching of marine ferromanganese precipitates Genetic implications, Geochim. Cosmochim. Acta, 59, 5113. 1995. 

Figure 13. Composition of sequential leaching solutions in a 2 1 mixture of water and composite soil A...

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). 

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