Speciation studies soil distribution

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... 

In soil research, the term speciation is often applied to operationally defined fractionation of heavy metals into five or more components.25 Typically, water soluble, exchangeable, organically bound (which includes what is in biomass), amorphous oxide bound, crystalline oxide bound, and residual fractions are measured.26 Sometimes residual fractions are further subdivided according to particle size distributions to give amounts in sand, silt, and clay fractions. Similar fractionation procedures are often applied to aquatic sediments.27 In arid regions, often the calcium carbonate bound fractions of heavy metals are also measured.28 Because of the constraints of detection limits, generally only cadmium, copper, iron, manganese, and zinc are usually monitored by flame spectrometry in such heavy metal speciation studies.28... 

An earlier study on the speciation of heavy metals and geochemical mapping of the total metal content of the surface soils of Delhi7 showed the total Al content to vary between 1.87 to 5.34% with a mean of 3.57%. In view of the above, the objective of this research was to ascertain primarily the status of Aluminum in Delhi soils by studying its chemical speciation in the soil profile in order to improve the understanding of its distribution in the solid-phase pool of the soil. More precisely, the objectives were ... 

The pH-dependent speciation of U in soil and aqueous systems has been extensively studied (Grenthe et al, 1992 Fjeld et al, 2002 Wang et al, 2002), and several reports showed that the form of U greatly influences its uptake and distribution in plant tissues (Bondietti and Sweeton, 1977 Sheppard and Evenden, 1988 Mortvedt, 1994 Ebbs et al, 1998) as well as its uptake and accumulation by microorganisms (Suzuki and Banfield, 1999). Uranium may also be adsorbed... 

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