Traces Elements

Trace element geochemistry distribution of transition metals in the Earth s crust 

The classification of chemical elements into major and minor or trace element categories is somewhat arbitrary. Thermodynamically, a minor element may be defined as one that is partitioned between coexisting phases in compliance with laws of dilute solutions, such as Henry s law, eq. (7.2b). In geochemical parlance, however, trace elements are usually categorized on the basis of abundance data. In this context, the mineral, rock or environment containing the chemical elements must be defined as well as the concentration boundary separating a major and trace element. 

Trace elements in seawater are taken to be those that are present in quantities less than 1 mg excluding the nutrient constituents. The distribution and behaviour of minor elements have been reviewed in the light of data that conform to an oceanographically consistent manner. 

No consistent pattern for depth profiles of trace elements exists. Conservative elements trend with salinity variations provided they have no significant submarine sources. Non-conservative elements may exhibit peak concentrations at different depths in oxygenated waters as 

The criteria for an element, such as Pb, to exhibit a maximum concentration in surface waters are that the only significant input must be at the surface (aeolian supply) and it must be effectively removed from the water column. Constituents such as As, Ba, Cd, Ni and Zn exhibit nutrient type behaviour. Those elements (Cd) associated with the soft parts of the organism are strongly correlated with phosphate and are 

Several trace elements are essential for a healthy life. One example is iodine, which is needed to make the thyroid hormone. An iodine deficiency leads to goitre. This disease was once called Derbyshire throat as it was once common in that county. Goitre was common in inland areas where the soil is low in iodine and access to seafood is poor. 

While some trace elements are essential for a good health an excess is undesirable. This is particularly so with elements that are low in solubility as the body is unable to remove the excess. 

Selenium is an essential trace element for optimal health but an excess is toxic. The British population is now reckoned to be selenium deficient because more European wheat is now used to make bread at the expense of North American wheat. The difference in the selenium content is caused by the difference in the selenium content of the soils. In geological terms, European soil is older and the selenium has washed out. 

Modern analytical methods are so sensitive that low levels of many elements that would be toxic at higher levels can be found, e.g. arsenic. At one time some US states had laws banning any food with measurable quantities of arsenic. At this time, lead arsenate was used as an insecticide - if arsenic was present in measurable quantities then insecticide residues were present. However, such low levels of arsenic are not a health problem. 

The importance of trace elements in plant nutrition is most appreciated when plants are grown in culture solutions circulated past their root systems (hydroponics). This is a form of horticultural crop production that is rapidly increasing, especially where the solutions can be replenished automatically with nutrients. 

Boron deficiency is most often seen in root vegetables and sugar beet where it causes a problem of growing-point necrosis. Soils can be tested for boron levels and remedial action shoitld be taken before crops are grown. Sprays of boron or boronated fertilisers can be used where necessary. 

Copper deficiency is a problem of peaty, very light sandy and thin organic chalky soils. Symptoms are most often seen in wheat and barley where it produces shrivelled leaf and ear tips. Chelated copper can be applied directly to crops or copper sulphate apphed to soils. 

The poly-Si CMP process is very sensitive to trace metals. Copper, iron, nickel, and other similar metals are forbidden during this process as they can poison 

To avoid contamination of seawater with trace elements during sampling, samplers should meet the following conditions  

In addition to appropriate samplers, components of an optimum sampling system for trace element studies involve plastic (coated) wires , such as made of Kevlar, or plastic coated hydrowires, serial winches with plastic drums and plastic-coated bottom weights and messengers. 

Trace element analysis of foods can be carried out to check for contamination by toxic elements, such as lead and cadmium, or to determine beneficial micronutrients, or as an aid to distinguishing geographical origin. In fats, small numbers of trace elements are measured after digestion of the sample in acid followed atomic absorption spectrophotometry (AAS) or by direct graphite furnace vaporization. An AAS procedure for measuring lead in edible oils and fats has been collaboratively trialed with cocoa butter as a test material (Firestone, 1994). 

Kohiyama et al. (1992) reported mean levels of nickel, iron and copper of 0.03, 0.30 and 0.04 mg/kg, respectively, in 10 samples of cocoa butter. Baxter et al. (2001) found comparable results from the determination of 23 elements in 42 cocoa butters and 22 CBA fats, mostly of known geographical origin and processing history, by the sensitive multi-element technique of inductively coupled MS. No distinction could be made between the cocoa butters based on geographical origin or deodorization, and the very low levels of most elements in the CBA fats meant that their presence in mixtures with cocoa butter could not be detected. 

Hernandez et al. (1994) used AAS with acid digestion to measure copper, zinc, iron, magnesium and manganese in four South American and 15 African cocoa butters. The much higher levels reported (e.g. iron, 20-50 mg/kg, copper, 11-27 mg/kg) were ascribed to contamination by metals from grinding tools. Principal component analysis could not distinguish between samples from different continents or countries. 

Sulfur in canola oil is in the form of organic compounds as the decomposition products of glucosinolates. Although these sulfur components occur in trace quantities, they poison catalysts used for hydrogenation as well as giving a characteristic odour to the oil. Recent developments in analytical methods for sulfur determination revealed that soybean, sunflower and even coconut oils all contain sulfur at the level of 2-10 mg/kg. Only Brassica oils contain significant quantities of divalent sulfur components. Crude canola oils may contain 15-35 mg/kg of sulfur, while in RBD canola oils the amount of 

Oil sample Phosphorus Iron Calcium Sulfur Zinc Lead 

Typical chemical composition of crude, refined and deodorized canola oils is presented in Table 4.12. The deodorized oil data represents the oil quality as it is used as a food ingredient. The data are based on Canadian experience. 

The values for crude oil compare closely with those of other commercial oils, such as soybean oil, produced according to good extraction practice. An exception is the presence of chlorophylls and sulfur compounds that can be higher in canola oil than in most other commodity oils. The deodorized oil data reflect good refining practice and are similar to the data obtained with other deodorized commodity oils processed for food applications. 

The stability of canola oil is limited mostly by the presence of linolenic acid, chlorophyll and its decomposition products and other minor components with high chemical reactivity, such as trace amounts of fatty acids with more than three double bonds. These highly unsaturated fatty acids can be formed during refining and bleaching (Chapman et al. 1994). The presence of 7-11% of linolenic acid in the triacylglycerols of canola oil places it in a similar category to soybean oil with respect to flavour and oxidative stability. The deterioration of flavour as the result of auto- and photo-oxidation of unsaturated fatty acids in oils and fats is referred to as oxidative rancidity. 

The carboxylic acid reductase in acetogenic Clostridia such as Clostridium thermoaceti-cum (White et al. 1989 Strobl et al. 1992). 

The acetylene hydratase of Pelobacter acetylenicus (Rosner and Schink 1995). 

Tungsten may be incorporated into some proteins of purinolytic Clostridia (Wagner and Andreesen 1987), and into formyhnethanofuran dehydrogenase in Methanobacterium thermoautotrophicum (Bertram et al. 1994). 

Ferredoxin rednctases in Pyrococcus furiosus inclnding aldehyde ferredoxin reductase, glyceraldehyde-3-phosphate ferredoxin oxidorednctase, and formaldehyde ferredoxin reductase (Roy et al. 1999). 

It should be noted, however, that whereas the production and activity of some enzymes in Thermo toga maritima was stimulated by tungstate, the purified enzymes apparently did not contain tungsten. 

A coarse graphic intergrowth of quartz and potash feldspar of small optic angle that appears to be sanidine is typical. Quartz is also found in graphic intergrowth with more sodic extensions of plagioclase. Pegmatite differentiates are common in all thick basic sheets and those of the Ferrar Dolerites display the usual features of such bodies, as described by Walker (1953). 

Trace element concentrations of the Vanda hypersthene sill measured by Gunn (1966) include chromium, nickel, copper, zinc, rubidium, strontium, zirconium, and barium. Gunn (1966) also reported concentrations of the same trace elements in the New Mountains pigeonite sill and in the Thumb Point olivine sill. The profiles of nickel and copper concentrations in Fig. 13.11 reveal that the rocks of the mafic zone of the Vanda hypersthene-sill are enriched in nickel and depleted in copper. The concentration of nickel decreases up-section in the felsic zone and 

The anticorrelation of nickel and copper indicates that these elements reside in different minerals. Nickel is closely correlated with magnesium (not shown) which indicates that it resides in pyroxene, whereas copper is correlated with zinc (not shown) and both elements may occur in sulfide minerals. 

Gunn (1966) concluded that the stratigraphic variation of the chemical composition, and hence of the mineral assemblages, support the view that the sills of 

13 Ferrar Group Dolerite Sills and the Dufek Intrusion 

Iron-deficiency anaemia is not common in lambs and calves because in practice it is unusual to restrict them to a milk diet without supplementary feeding. It does, however, sometimes occur in laying hens, since egg production represents a considerable drain on the body reserves. 

Iron is widely distributed in foods. Good sources of the element are green leafy materials, most leguminous plants and seed coats. Feeds of animal origin, such as blood and fishmeals, are excellent sources of iron. As mentioned previously, milk is a poor source of the element. 

The adult s need for iron is normally low, as the iron produced from the destruction of haemoglobin is made available for haemoglobin regeneration, only about 10 per cent of the element escaping from this cycle. 

Iron toxicity is not a common problem in farm animals, but it can result from prolonged oral administration of the element. Ferrous ions are reported to generate oxygen-based free radicals, contributing to oxidative stress in the cell (see Chapter 5). Normally iron is protein-bound or in chemical form, which prevents it from causing oxidation. Chronic iron toxicity results in alimentary disturbances, reduced growth and phosphorus deficiency. 

Copper plays an important role in the production of crimp in wool. The element is present in an enzyme that is responsible for the disulphide bridge in two adjacent cysteine molecules. In the absence of the enzyme, the protein molecules of the wool do not form their bridge and the wool, which lacks crimp, is referred to as stringy or 

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The relative simplicity of tlie method and the penetrative nature of the x-rays, yield a technique that is sensitive to elements with Z > 10 down to a few parts per million (ppm) and can be perfonued quantitatively from first principles. The databases for PIXE analysis programs [21, 22 and 23] are typically so well developed as to include accurate fiindamental parameters, allowing the absolute precision of the technique to be around 3% for major elements and 10-20% for trace elements. A major factor m applying the PIXE teclmique is that the bombardmg energy of the... 

Typically, PIXE measurements are perfonned in a vacuum of around 10 Pa, although they can be perfonned in air with some limitations. Ion currents needed are typically a few nanoamperes and current is nonnally not a limiting factor in applying the teclmique with a particle accelerator. This beam current also nonnally leads to no significant damage to samples in the process of analysis, offering a non-destmctive analytical method sensitive to trace element concentration levels. 

Figure Bl.24.15. An example of a PIXE spectmm. This spectmm was obtained from the analysis of a piece of ivory to establish whether the origm of the ivory could be detennined from trace element concentrations.

Manganese is widely distributed throughout the animal kingdom. It is an important trace element and may be essential for utilization of vitamin Bl. 

Gallium is often found as a trace element in diaspore, sphalerite, germanite, bauxite, and coal. Some flue dusts from burning coal have been shown to contain as much 1.5 percent gallium. 

Elemental selenium has been said to be practically nontoxic and is considered to be an essential trace element however, hydrogen selenide and other selenium compounds are extremely toxic, and resemble arsenic in their physiological reactions. 

Vandecasteele, G. Block, G. B. Modern Methods for Trace Element Determination. Wiley Ghichester, England, 1994. 

Isotopic dilution analysis is widely used to determine the amounts of trace elements in a wide range of samples. The technique involves the addition to any sample of a known quantity (a spike) of an isotope of the element to be analyzed. By measuring isotope ratios in the sample before and after addition of the spike, the amount of the trace element can be determined with high accuracy. The method is described more fully in Figure 48.13. 

For the purposes of this illustration, suppose that the level of of a trace element (X) is to be determined in a sample and that the element has two suitable isotopes (A,B). 

Bloremedia.tlon. Cmde oil and refined products are readily biodegradable under aerobic conditions, but they are only incomplete foods siace they lack any significant nitrogen, phosphoms, and essential trace elements. Bioremediation strategies for removing large quantities of hydrocarbon must therefore iaclude the addition of fertilisers to provide these elements la a bioavailable form. 

The mercury cell operates efficiently because of the higher overpotential of hydrogen on mercury to achieve the preferential formation of sodium amalgam. Certain trace elements, such as vanadium, can lower the hydrogen overpotential, however, resulting in the release of hydrogen in potentially dangerous amounts. 

Cobalt, copper, molybdenum, iodine, iron, manganese, nickel, selenium, and zinc are sometimes provided to mminants. Mineral deficiency or toxicity in sheep, especially copper and selenium, is a common example of dietary mineral imbalance (21). Other elements may be required for optimal mminant performance (22). ExceUent reviews of trace elements are available (5,22). 

There are several possible reasons why a scientific study of an art work may be desirable. An obvious one is in cases where the authenticity of an object is doubted on styHstic grounds, but no unanimous opinion exists. The scientist can identify the materials, analy2e the chemical composition, and then investigate whether these correspond to what has been found in comparable objects of unquestioned provenance. If the sources for the materials can be characterized, eg, through trace element composition or stmcture, it may be possible to determine whether the sources involved in the procurement of the materials for comparable objects with known provenance are the same. Comparative examination of the technological processes involved in the manufacture allows for conclusions as to whether the object was made using techniques actually available to the people who supposedly created it. Additionally, dating techniques may lead to the estabUshment of the date of manufacture. 

Trace-element analysis of metals can give indications of the geographic provenance of the material. Both emission spectroscopy (84) and activation analysis (85) have been used for this purpose. Another tool in provenance studies is the measurement of relative abundances of the lead isotopes (86,87). This technique is not restricted to metals, but can be used on any material that contains lead. Finally, for an object cast around a ceramic core, a sample of the core material can be used for thermoluminescence dating. 

Trace-element analysis, using emission spectroscopy (107) and, especially, activation analysis (108) has been appHed in provenance studies on archaeological ceramics with revolutionary results. The attribution of a certain geographic origin for the clay of an object excavated elsewhere has a direct implication on past trade and exchange relationships. 

National Institute of Standards and Technology (NIST). The NIST is the source of many of the standards used in chemical and physical analyses in the United States and throughout the world. The standards prepared and distributed by the NIST are used to caUbrate measurement systems and to provide a central basis for uniformity and accuracy of measurement. At present, over 1200 Standard Reference Materials (SRMs) are available and are described by the NIST (15). Included are many steels, nonferrous alloys, high purity metals, primary standards for use in volumetric analysis, microchemical standards, clinical laboratory standards, biological material certified for trace elements, environmental standards, trace element standards, ion-activity standards (for pH and ion-selective electrodes), freezing and melting point standards, colorimetry standards, optical standards, radioactivity standards, particle-size standards, and density standards. Certificates are issued with the standard reference materials showing values for the parameters that have been determined. 

E. A. Noble, N. Dakota Geol Survey Bull 63, 80—85 (1973) D. G. Wyant and E. P. Beroni, Reconnaissance for Trace Elements in North Dakota and... 

Chemiluminescence has been studied extensively (2) for several reasons (/) chemiexcitation relates to fundamental molecular interactions and transformations and its study provides access to basic elements of reaction mechanisms and molecular properties (2) efficient chemiluminescence can provide an emergency or portable light source (J) chemiluminescence provides means to detect and measure trace elements and pollutants for environmental control, or clinically important substances (eg, metaboHtes, specific proteins, cancer markers, hormones, DNA) and (4) classification of the hioluminescent relationship between different organisms defines their biological relationship and pattern of evolution. 

Health and Environment. Manganese in trace amounts is an essential element for both plants and animals and is among the trace elements least toxic to mammals including humans. Exposure to abnormally high concentrations of manganese, particulady in the form of dust and fumes, is, however, known to have resulted in adverse effects to humans (36,37) (see Mineral nutrients). 

Potassium removal is required because the presence of potassium during electrolysis reportedly promotes the formation of the a-Mn02 phase which is nonbattery active. Neutralization is continued to a pH of approximately 4.5, which results in the precipitation of additional trace elements and, along with the ore gangue, can be removed by filtration. Pinal purification of the electrolyte Hquor by the addition of sulfide salts results in the precipitation of all nonmanganese transition metals. 

Trace Mercury. There are a number and variety of methods and instmments to determine trace quantities of both inorganic and organic mercury ia natural or synthetic substances (19) (see also Trace and residue analysis). Literature describiag numerous techniques and trace element analysis of a myriad of mercury-containing substances is available (20). Only the most commonly used methods are mentioned hereia. 

Fluorescence Microscope. A useful light microscope utilizes UV light to induce fluorescence in microscopic samples (40). Because fluorescence is often the result of trace components in a given sample rather than intrinsic fluorescence of the principal component, it is useful in the crime laboratory for the comparison of particles and fibers from suspect and crime scene. Particles of the same substance from different sources almost certainly show a different group of trace elements. It is also very useful in biology where fluorescent compounds can be absorbed on (and therefore locate and identify) components of a tissue section. 

Iron. The total body content of iron, ie, 3—5 g, is recycled more efficientiy than other metals. There is no mechanism for excretion of iron and what Httie iron is lost daily, ie, ca 1 mg in the male and 1.5 mg in the menstmating female, is lost mainly through exfoHated mucosal, skin, or hair ceUs, and menstmal blood (74—76). Common food sources rich in iron and other trace elements are Hsted in Table 10. 

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