Environmental and Geological Materials

The extremely wide range of materials of concern, including foods, feeds, clinical, geological, atmospheric, metals, alloys and industrial products can be surmised from an example of a material classification scheme presented in Table 2.1. The emphasis is on naturally occurring materials (mostly biological), but there is a cross-over between environmental and anthropogenic materials in the listing. 

Kenneth Barbalace Includes a chemical and environmental dictionary a detailed periodic table of elements articles on environmental and hazardous materials issues a geologic timeline. http //environmentalchemistry.com/... 

Environmental scientists such as those involved in performance assessment (e.g., for nuclear repositories) would be pleased to be able to predict the interactions of solutes (e.g., radionuclides) with backfill and geologic materials. However, in this area, which in many countries receives much public attention, even the aqueous solution equilibria for the pertaining conditions of a favored repository concept cannot be accurately described (e.g., metal ions in brine solutions, which require Pitzer formalism, or in highly alkaline backfill pore waters, which have traditionally not received much attention in aqueous solution studies because of the limitations of glass electrodes and solid phase formation). Databases for surface complexation applications are also required for many other purposes, but the major drawback of such potential databases is that no agreement exists on the actual surface complexation model to be used. This may ultimately lead to particular difficult situations whenever one of the following occur ... 

The Table shows a great spread in Kd-values even at the same location. This is due to the fact that the environmental conditions influence the partition of plutonium species between different valency states and complexes. For the different actinides, it is found that the Kd-values under otherwise identical conditions (e.g. for the uptake of plutonium on geologic materials or in organisms) decrease in the order Pu>Am>U>Np (15). Because neptunium is usually pentavalent, uranium hexavalent and americium trivalent, while plutonium in natural systems is mainly tetravalent, it is clear from the actinide homologue properties that the oxidation state of plutonium will affect the observed Kd-value. The oxidation state of plutonium depends on the redox potential (Eh-value) of the ground water and its content of oxidants or reductants. It is also found that natural ligands like C032- and fulvic acids, which complex plutonium (see next section), also influence the Kd-value. 

A remarkable level of activity can be seen in China. The National Research Center for CRM (NRCCRM) was founded in 1980 and the certification and accreditation program for CBW RMs started in 1983 by co-operation with many Chinese Institutions. In 1993 around 60 RMs and CRMs were available (Chai Chifang 1993) and in 1999 the availability of about 1000 CRMs was reported, around 30 of them clinical, 100 environmental, 200 geological, and 300 metallic matrix materials (Rong and Min 1999). 

Kucera j (1995) Elemental characterization of new Polish and US NIST geological, environmental and biological reference materials by neutron activation analysis and comments on the methodology of interlaboratory comparisons. Chem Anal (Warsaw) 40 405-421. 

X-ray fluorescence can be used to analyse all types of samples. Its applications are numerous, whether in research and development or in quality control of production. Initially, X-ray fluorescence was used in industries that treat metals of primary fusion or alloys and, more generally, in the mineral industry (for use one ceramics, cements, steel, glass, etc.). Because of the ease of use of common X-ray fluorescence instruments, its scope of application has expanded into other areas the photographic industry and semi-conductors (for impurity control in silicon chips), the petroleum industry, geology, paper mills, gas analyses (such as nitrogen), toxicology and environmental applications (dust, fumes from combustion, heavy metals, and dangerous materials in waste such as Pb, As, Cr, Cd, etc.). 

An important precursor of valid measurement, and the establishment of measurement traceability, is an adequate description of what is to be measured (the measurand), which includes the measurement units and consideration of the acceptable level of measurement uncertainty (MU). Clearly, if different characteristics are measured, or different measurement units are employed, then different measurement results can be expected. Clarity on this issue can be vital to subsequent decision making. For example, in environmental studies, it may be more important to know the amount of extractable pollutant in a geological material, rather than the total amount of the pollutant. Thus, although self evident when we think about it, it is important to remember that, in addition to making traceable measurements, it is also important to make the right type of measurement. 

Hard X-ray Spectroscopy. Hard X-ray spectroscopy has been applied in a wide variety of scientific disciplines (physics, chemistry, life sciences, and geology) to investigate and image geometric and electronic structures. The method is element, oxidation, state, and symmetry specific. The technique has been particularly useful in the characterization of new materials. It has also been used in the elucidation of chemical speciation in dilute samples of environmental concern. 

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