Toxic trace element concentrations

Sediment Analysis. Sediment is the most chemically and biologically active component of the aquatic environment. Benthic invertebrate and microbial life concentrate in the sediment, a natural sink for precipitated metal forms, and an excellent sorbent for many metal species. TTie extent to which potentially toxic trace element forms bind to sediment is determined by the sediment s binding intensity and capacity and various solution parameters, as well as the concentration and nature of the metal forms of interest. Under some conditions sediment analyses can readily indicate sources of discharged trace elements. 

Methods. As discussed in the previous chapter, a number of approaches have been used to assess the presence of potentially toxic trace elements in water. The approaches used in this assessment include comparative media evaluation, a human health and aquatic life guidelines assessment, a mass balance evaluation, probability plots, and toxicity bioassays. Concentrations of trace elements were determined by atomic absorption spectrometry according to standard methods (21,22) by the Oregon State Department of Environmental Quality and the U.S. Geological Survey. 

Comparative Media Evaluation. Table 4 is a summary of trace element occurrences for water, sediment, fish and rocks in Oregon as compared with concentrations measured elsewhere in the world. Details of the comparison parameters are provided in the footnotes to Table 4. The table indicates that no excessively high concentrations of potentially toxic trace elements exist in Willamette River water relative to "uncontaminated sites. 

Table 8.10 shows the concentration range of potential toxic trace elements in U.S. sewage sludges, as summarized by Chaney (1989). In this table, data on maximum concentration of toxic trace elements in dry, digested sewage sludges are compared to concentrations of the elements in median sludges and in soils. The subsurface contamination that may result from uncontrolled disposal on land surfaces... 

Natusch, D. F. S., Wallasce, J. R. Evans, C. A. 1974. Toxic trace elements Preferential concentration in respirable particles. Science, 183, 202-204. 

Complicated biological systems (bioassays) at trace element concentration levels typical for offshore waters, are subject to serious danger of contamination. Without extreme precautions e.g. Carpenter and Lively (1980) and Fitzwater et al. (1982) found the toxic effect (inhibition of primary production) of contamination by the incubation bottles. Effects of adsorption to walls and particulate matter (sediment) should not be underestimated. Use of clean lab techniques and regular check of the trace element concentrations throughout the (biological) experiments is necessary to get an indication of the actual concentration and possible distribution of the different elements. Depending on the type of experiments it could be possible that other parametes should be known or even controlled pE, PO2, ionic strength, temperature, DOC etc. 

Measurement of toxic and essential trace element concentrations in foods and prepared meals and... 

Toxic and essential trace elements intakes were computed from food consumption data of the population in northern Italy and element concentration measurements. The results (Table 10.6) were compared with the Italian Recommended Dietary Allowance (RDA) for essential trace elements and with the Provisional Tolerable Daily/Weekly Intake (PTDI/PTWI) for toxic elements. Finally, an assessment was made of the extent to which each food contributes to the total intake of trace elements by the population under study and the most contaminated foods were also detected. On the whole, mean intake values satisfied the Italian RDA for all the essential trace elements [31], while the potentially toxic trace elements were below the relevant threshold limits. 

P, 819-2589 and 789-1440 and Zn, 14.6-30.1 and 13.8-22.8. It could be concluded that Vietnamese rice has elemental concentration ranges largely overlapping those of Australian rice. Another fact worth mentioning is that Vietnamese rice has rather high concentrations of nutritional elements such as K, Mg, and P, whereas the levels of potentially toxic trace elements (e.g., Cd) are very low. Finally, the concentration of Ni was found to be higher in white than in brown... 

Manganese is also a toxic agent, though it can be regarded as one of the least toxic trace elements. A wide margin of safety exists between its intake which is essential for the organism and the concentrations associated with toxic effects (17). 

The objectives of studies of ambient and workplace air differ considerably. Ambient studies have been carried out to provide general knowledge, observe differences between locations, relate trace-element concentrations to sources, and seek correlations to other air pollution indices or to human health studies. Workplace measurements, on the other hand, are made to assure control of toxic materials at concentrations safe for the workers, as well as to seek better data on health effects. In the United States acceptable... 

CONCENTRATIONS OF NON-ESSENTIAL, TOXIC TRACE ELEMENTS IN BODY TISSUES AND FLUIDS... 

The forensic scientist employed in the analysis of specimens for metal concentrations is involved generally in two main areas of investigation. The first is in the determination of toxic metals in biological tissue in order to ascertain the cause of death or injury (homicidal or suicidal) in suspected poisoning cases. The second is to compare certain characteristic trace element concentrations in materials found at the scene of the crime with the same type of material found in the possession of the accused. A special case of this second approach is in the analysis of the elements barium,... 

Toxic trace elements were isolated from water samples by extraction with di-ethyldithiocarbamate (Table 2.1.2). Following this pre-concentration step the metal ions were adsorbed on a cation-exchange resin using a mixture of tetrahydro-furan-methylglycol-6 M HCl as sorption solution. The succesive elution was treated with 6 M HCl, 1 M HCl and 2 M HNO3 for fractional separation. In another application hexane-isopropanol-HCl mixture was used as the adsorption medium An analytical scheme which provides quantitative results, is described for ion-exchange separation of fifteen major, minor and trace elements in silicates For concentration and separation of copper, chromium, lead and iron an ion-exchanger in phosphate or OH -form was used in various combinations ... 

Three-quarters of the metal minerals are processed and mostly consumed in the relatively small highly industrialized countries which contain one-quarter of the world s population. The aerial concentration of processing and consumption causes environmental problems, and the risk of contaminating soils, rivers and air with toxic trace elements is high in industrialized countries. Beside the firing of coal and oil, processing of ores and the technical use of several metals is a major source of such contamination. 

The deposition and accumulation of fly ash downwind from coal-combustion sites is a concern because it may be significantly enriched in potentially toxic trace elements, including lead (Pb) and arsenic (As), compared to the burned coal (Coles et al, 1979 Eary et al, 1990 Hower et al, 1999 Kaakinen et al, 1975). Other elements such as zinc (Zn) and germanium (Ge), of less environmental concern, may also be enriched in fly ash. The relatively high concentrations of As in fly ash reflect partly its presence in pyrite in coal from the Appalachian Basin (Goldhaber et al, 2002). More importantly, the concentration of these metals and metalloids occurs during the combustion process itself. A suite of elements including As, Ca, Cr, Cu, Ga, Mo, Ni, Pb, Sb, Se, V, and Zn is enriched in the fine fraction of coal fly ash (Coles et al, 1979), because of vaporization in the furnace and subsequent condensation or absorption onto ash particles (Kaakinen et al, 1975). 

The transition elements are useful tracers in many geological systems. They are industrially important and form economic ores, especially in hydrothermal systems where they are often present as sulfide minerals. Cd, Hg, Zn, and Pb are persistent industrial pollutants and determination of low levels of these elements in ores and fossil fuels is critical as processing of ores or burning of fuels may concentrate and release toxic elements. The concentration of such toxic trace elements may affect the economic value of an ore or fossil fuel deposit significantly. 

Samples such as hair, nails, blood, urine, and various tissues are analyzed by NAA for both essential and toxic trace elements (Bhandari et al. 1987, Lai et al. 1987). The analysis can be related to determine their effect on disease outcomes. These authors have reported that the diet and environment contribute largely towards the trace elements in the human body. It is has been demonstrated in other works that the selenium concentration in human nails is an accurate monitor of the dietary intake of selenium. As a consequence, the nail monitor has been extensively used to study the protective effect of dietary selenium against cancer and heart disease in numerous prospective case-control studies. In another study by Kanabrocki et al. (1979) on human thumbnails in USA, using thermal NAA technique, the average concentration of metals studied in clinically symptom-free adult female and male subjects were found to be zinc, 184 vs. 153 ppm chromium, 6.8 vs. 4.2 selenium, 0.9 vs. 0.6 gold, 2.6 vs. 0.4 mercury, 1.9 vs. 0.4 silver 0.7 vs. 0.3 cobalt, 0.07 vs. 0.04. In another study, the fluorine concentration in bone biopsy samples was... 

The concentration and/or activity of dissolved Fe(III) is thus controlled by different mineral phases depending on the pH. This is illustrated in Fig. 3, which plots the pH-dependent variation in the concentration and speciation of dissolved iron in different mine pit lakes of the IPB. Among the 15 pit lakes studied, jarosite was only observed to precipitate in Corta Atalaya, so that this mineral controls the apparent equilibrium which seems to exist between dissolved and particulate Fe(ni) in this lake. Conversely, ferrihydrite is the mineral form under which Fe(III) precipitates in Los Frailes pit lake. Most lakes, however, seem to be at or near equilibrium with respect to schwertmannite, which not only controls the solubility of Fe(III), but also buffers the systems at pH 2.5-3.5 (through reaction (5)), and sorbs toxic trace elements like As [5-14, 24—28]. 

A prolonged intake of cadmium results in its accumulation in the human organism, primarily in fiver and kidney. A level of 0.2-0.3 mg Cd/g kidney cortex causes damage of the tubuli. The tolerable weekly dose for an adult (70 kg) is considered to be 0.49 mg of cadmium. On the whole, the concentrations of the toxic trace elements lead, mercury and cadmium in food show a clearly decreasing tendency, especially in recent studies. This is partly due to inprovements... 

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