Elemental distribution speciation

In recent years, several techniques based on synchrotron radiation have been applied to determine, with pm-spatial resolution, the elemental distribution and speciation of metals in mine-contaminated soils (Manceau et al. 2003 Morin et al. 1999, 2001). 

In 2006, Lobinski et al.1 reported on the imaging and speciation analysis of trace elements to study the element distribution, oxidation state, metal site and metal structure in biological environments using mass spectrometric techniques (LA-ICP-MS, SIMS, MALDI-MS) and non-mass-spectrometric techniques such as micro-PIXE (proton induced X-ray emission), XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) -the latter two techniques are very sensitive due the use of a more intense synchrotron beam.1... 

Wan, J., Tyliszczak, T., and Tokunaga, T. K. (2007). Organic carbon distribution, speciation, and elemental correlation within soil microaggregates Apphcation of STXM and NEXAFS spectroscopy. Geochim. Cosmochim. Acta 71, 5439-5449. 

In rivers and streams heavy metals are distributed between the water, colloidal material, suspended matter, and the sedimented phases. The assessment of the mechanisms of deposition and remobilization of heavy metals into and from the sediment is one task for research on the behavior of metals in river systems [IRGOLIC and MARTELL, 1985]. It was hitherto, usual to calculate enrichment factors, for instance the geoaccumulation index for sediments [MULLER, 1979 1981], to compare the properties of elements. Distribution coefficients of the metal in water and in sediment fractions were calculated for some rivers to find general aspects of the enrichment behavior of metals [FOR-STNER and MULLER, 1974]. In-situ analyses or laboratory experiments with natural material in combination with speciation techniques are another means of investigation [LANDNER, 1987 CALMANO et al., 1992], Such experiments manifest univariate dependencies for the metals and other components, for instance between different metals and nitrilotriacetic acid [FORSTNER and SALOMONS, 1991], but the interactions in natural systems are often more complex. 

Through the influence of speciation on oceanic input and removal processes it is expected that chemical form should strongly influence not only overall chemical concentrations in the ocean but also chemical distributions. In view of this expectation, assessments of speciation and comparative chemistries in this chapter are made in the context of vertical distributions (concentrations vs depth) of chemical species in the ocean. Since elemental distributions are influenced not... 

These observed differences in absorption of the element can be explained by the different distribution (speciation) of Cu in human and formula milks (see Fig. 17.10 and compare with Fig. 17.3). In premature formula milk whey, most Cu was distributed as follows a small amount in the HMW region (450 kDa) and a large amount in the LMW region (13 and <10 kDa), the latter corresponding to... 

Bundschuh, J., Bonorino, G., Viero, A.P., Albouy, R., and Fuertes, A. (2000). Arsenic and other trace elements in sedimentary aquifers in the Chaco-Pampean Plain, Argentina Origin, distribution, speciation, social and economic consequences. In Bhattacharya, P., Welch, A.H. (Eds.), Arsenic in Groundwater of Sedimentary Aquifers, Pre-Congress Workshop, 31st Internal. Geol. Cong., Rio de Janeiro, Brazil, pp. 27-32. 

Phase distribution (speciation) of elements in soils and bioavailability of various species. 

Molybdenum (Mo) is an essential element for many plants and animals (Newton and Otsuka, 1980). Because of its chemical properties. Mo readily provides sites for reactions and catalysis in biochemical systems (Haight and Boston, 1973). It is therefore important to understand the processes that control the distribution, speciation, and behavior of Mo in the surficial environment. These processes will affect the bioavailability of Mo and ultimately its passage into the food chain. 

Distribution, transport, metabolism, and detoxification studies of both essential and toxic trace elements via speciation information are becoming popular in ecotoxicology as well. 

Soil solution to soil ratios also strongly affect distribution of some trace elements such as Zn speciation in arid and semi-arid soils. Fotovat et al. (1997) reported that the proportion of free hydrated Zn2+ to total Zn ranged from 20-65% at field capacity soil water content and decreased with increases in solution to soil ratios, while the proportion of Zn complexed with organic ligands increased dramatically in soils. However, solution to soil ratios do not strongly affect the distribution of Cu speciation in soil solution since Cu primarily occurs as organic complexes in these soil solutions. 

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. 

As noted above, biouptake involves a series of elementary processes that take place in the external medium, in the interphasial region, and within the cell itself. One of the most important characteristics of the medium is the chemical speciation of the bioactive element or compound under consideration. Speci-ation not only includes complexation of metal ions by various types of ligands, but also the distribution over different oxidation states, e.g. Fe(II) and Fe(III), and protonation/deprotonation of organic and inorganic acids of intermediate strength. The relationship between speciation and the direct or indirect bioavailability1 of certain species has received a lot of recent attention. 

The factors which control the distribution of trace elements [defined arbitrarily in geochemistry as those elements present at less than 0.1 weight percent (wt %)] can be discussed under a number of headings - structural, thermodynamic, kinetic and, in the sedimentary environment, solubility and speciation. 

Model Studies. In model studies of adsorption, one deals with simple, well-defined systems, where usually a single well-characterized solid phase is used and the composition of the ionic medium is known, so that reactions competing with the adsorption may be predicted. It is not a trivial problem to compare the results from such model studies with those from field studies, or to use model results for the interpretation of field data. In field studies, a complex mixture of solid phases and dissolved components, whose composition is only poorly known, has to be considered competitive reactions of major ions and trace metal ions for adsorption may take place, and the speciation of the trace metal ions is often poorly understood. In order to relate field studies to model studies, distribution coefficients of elements between the dissolved and solid phases are useful. These distribution coefficients are of the following form ... 

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