Enriched elements

A common approach for identifying the enriched elements in a material is to calculate the enrichment factor (EF). The EF of an element, M, is obtained by comparing its concentration with that of a reference element, R, such as cerium or... 

In summary, coal-fired power plants appear not to be the major source of most enriched elements on particles In urban areas, despite the great attention devoted to mechanisms by which those elements become preferentially attached to fine particles (e.g.. Refs. 18, 34). However, the detailed studies of processes In coal-fired plants are of considerable value, as the fundamentals should be applicable to other kinds of combustion sources. Furthermore, It may be necessary to use this fundamental approach to develop methods for predicting the source compositions for coal-fired power plants that have not been measured. Selenium Is much... 

Inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) is a well-known analytical technique based on the measurement of isotope ratios in samples where their isotopic composition was altered by the addition of a known amount of an isotopically enriched element. 

For lithophiles such as Sc, V, Cs, Fe and Hf, whose EFcrust values are near one, the EFcoa] values are also near one, but generally have somewhat smaller fluctuations. Sodium and Mn, which are depleted with respect to soil, have EFcoai values of about 1, as is expected from the depletion of these elements in coal. Many enriched elements, such as S, Co, Zn, As, Se, Mo, Cd, Sb, I, W and Pb, are much less enriched with respect to coal than to soil because of the considerable enrichment of these elements in the coal itself relative to crustal material. However, most of these, especially S, As, Se, Mo and Cd, are still more enriched in plant emissions than in coal, so a knowledge of coal composition does not suffice to explain their behavior in stack emissions. 

Figure 4. Enrichment factors for fine and coarse particles from eastern U.S. plants equipped with ESPSo Plants included are ORV(A), (B), and (C) Chalk Point and Eddystone for coarse particles, and the same plants plus Dickerson for coarse particles. Note that the y-scale is logarithmic for the more enriched elements. Range shown for each element is from Xg/aq to Xg-ag, where xg and ag are geometric means and standard deviations.

Highly negative values of k in addition imply the possibility to retain or even enrich elements which will form but rather labile complexes given the effective electrochemical ligand parameter of the plant species and (Eq. 2.11). These include Sr, Ba or Mn and the REEs (except of Sm, Tb) if E (L) j is close to zero in the latter case, all of which are known to be hyperaccumulated in some plants, e.g. Ba and Mn in Brazil nuts (Emsley 2001) and - among our test set of plant species - Mn gets substantially enriched in blueberries (both leaves (to which data reported here (Markert 1996) pertain) and fruits), k thus is a kind of measure for amplification of differences in the sequence of transport within some plant, from sequestration in/ by root exudates to deposition in the tips of leaves. 

Weathering and erosion at the Earth s surface preferentially removes those elements that are water soluble (e.g., strontium, calcium, barium, magnesium) from the continental mass, and enriches elements that are adsorbed onto clay minerals (e.g., rubidium, REE ). One way to isolate the effects of igneous and sedimentary processes is therefore to use trace-element ratios... 

Figures 16(a) and (b), respectively. Most of elements are enriched in metalliferrous ridge and basal sediments relative to shale, with the exception of some elements with values around one that are mostly contributed by shale. For example, A1 and Ti in metalliferous ridge sediments and Al, Si, K, Cr, Ga, Rb, Nb, Sn, Ce, Hf, Bi, and Th in metalliferous basal sediments are mostly contributed by shale (Figure 16(a)). The enriched elements are either contributed from nearby hydrothermal vent solutions or by seawater or both. If one assumes that manganese in metalliferrous ridge and basal sediments is all of vent origin, then the elements with Mn [sample/ hydrothermal vent] values of one or less in metalliferous sediments can be fully supplied by hydrothermal vent solution. These elements include Li, B, Si, K, Mn, Fe, Cu, Zn, Se, Ag, Cd, and Pb in Figure 16(b). Elements with Mn greater than 2 are mostly supplied by seawater, such as Be, Co, As, Ba, and REEs (Eigure 16(b)). Indeed, Bender et al. (1971) showed that the REE distribution pattern in the metalliferrous...

Freund, H., Yoshimura, N., Fischer, J.E. Chronic hepatic encephalopathy. Long-term therapy with a branched-chain amino-acid-enriched elemental diet. X. Amer. Med. Ass. 1979 242 347-349... 

Generally, five types of elements have been distinguished according to their distribution in sediment cores from Lake Erie (Kemp et al., 1976) (i) Diagenetically mobile elements such as Fe, Mn and sulfur (ii) carbonate elements, carbonate-c and calcium (iii) nutrient elements, organic C, H, and P (iv) enriched elements, such as Cu, Cd, Zn Pb, and Hg and (v) conservative elements, e.g. Si, K, Ti, Na, and Mg. Comparison of group (iv) elements of environment concern with "conservative" elements (v) seem to be particularly useful for the reduction of grain size effects, since no separation step is required. 

Rahn (1975) has summarized data for many highly enriched elements. From a limited number of elemental mass-size distributions, Rahn (1975a)... 

Boron-10 isotopic labeling of boron compounds is more useful than nB labeling since the latter isotope is more abundant in nature (80.39%). Commercially available starting materials for 10B labeling are 10B-enriched elemental boron or boric acid. The 10B content may be higher than 90%, and it is convenient for mechanistic studies to use a material containing 93.7% 10B and 6.3% nB. 

As is the case with isotopic labeling of molecules, enriched levels of stable isotopes of elements can be used as tracers. Isotopes of elements can be used as nutritional supplements for plants or animals to trace absorption, assimilation, and metabolism of elements (Allen and Georgitis). Processes such as biomethylation of elements like mercury and arsenic in the environment can be studied using isotopically enriched elements. In some cases, methylated metals are more toxic than the inorganic species, and generally accumulate up the food chain. 

As it was mentioned, boron carbide containing enriched elemental boron ( B 65 at%) can serve as the control rod material in fast breeder nuclear reactors. Because boron carbide is fabricated by reacting elemental boron with carbon and the elemental boron in turn is produced by electro-winning process, Jain et al. (2011) have carried out studies to explore the viability of a high-temperature molten salt electro-winning process for the large-scale production of °B isotopically enriched elemental boron. It was established that elemental boron powder with a purity of better than 95 wt% could be produced. 

The first ever application of a radiotracer in a biological experiment dates back to 1923 when George de Hevesy used Pb to study plant uptake of lead from solution [5]. His seminal work was honored by the Nobel Prize in Chemistry in 1943 and made him the father of isotope tracing, a tool that is still indispensable in virtually any area of scientific research. The first use of a stable isotope to study mineral metabolism was reported in 1963, when Lowman and Krivit injected stable Fe together with radioactive Fe into a human subject to compare the plasma clearance of the two isotopes [6]. However, it was not until the 1980s that stable isotope techniques were explored systematically to study mineral and trace element metabolism in humans. This was not only due to the increasing recognition of health hazards associated with the use of radioisotopes. Mass spectro-metric techniques had to be refined to measure isotope ratios of the heavier elements at a precision suitable for the exploitation of isotopically enriched elements as tracers. Stable isotopic labels are made up from the same isotopes as the natural element, from which they differ only in terms of composition, that is, in the relative abundances of their isotopes. 

Eb = 320GPa, Em = 20GPa, Vb = = 0-25 FRAC2D mesh consists of enriched elements at the crack tip and cubic elements elsewhere ... 

---