Arsenic trace element

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. 

Trace contaminants in the phosphoms may be deterrnined by oxidation of the phosphoms by various techniques. The metals are then deterrnined by an inductively coupled plasma spectrophotometer or by atomic absorption. The most important trace metal is arsenic, which must be reduced in concentration for food-grade products. Numerous other trace metals have become important in recent years owing to the specifications for electronic-grade phosphoric acid requited by the semiconductor industry (see Electronic materials Semiconductors). Some trace elements must be reduced to the low ppb range in phosphoric acid to comply. 

Zinc smelters use x-ray fluorescence spectrometry to analyze for zinc and many other metals in concentrates, calcines, residues, and trace elements precipitated from solution, such as arsenic, antimony, selenium, tellurium, and tin. X-ray analysis is also used for quaUtative and semiquantitative analysis. Electrolytic smelters rely heavily on AAS and polarography for solutions, residues, and environmental samples. 

The procedure followed describes methods for the determination of total levels, and in certain cases, available amounts of trace elements in soils. The determination of arsenic in soil by hydride generation AAS is included. 

Andreae, M. O. (1979). Arsenic speciation in seawater and interstitial waters the role of biological-chemical interactions on the chemistry of a trace element. Limnol. Oceanog. 24,440-452. 

Stoeppler M, Vahter M (1994) Arsenic. In Herber RFM, Stoeppler M, eds. Trace element analysis in biological specimens. Elsevier, Amsterdam. 

Zheng, J., Kosmus, W., Pichler-Semmelrock, F., and Kock, M., Arsenic speci-ation in human urine reference materials using high-performance liquid chromatography with inductively coupled plasma mass spectrometric detection, /. Trace Elements Med. Biol., 13, 150, 1999. 

In the wetlands of Idaho, the formation of an Fe(III) precipitate (plaque) on the surface of aquatic plant roots (Typha latifolia, cat tail and Phalaris arundinacea, reed canary grass) may provide a means of attenuation and external exclusion of metals and trace elements (Hansel et al, 2002). Iron oxides were predominantly ferrihydrite with lesser amounts of goethite and minor levels of siderite and lepidocrocite. Both spatial and temporal correlations between As and Fe on the root surfaces were observed and arsenic existed as arsenate-iron hydroxide complexes (82%). 

Eight trace elements of greatest environmental concern are chosen, which are arsenic (As), mercury (Hg), lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni), copper (Cu) and zinc (Zn). These eight trace elements will be discussed in this chapter in the order of their production and level of environmental concern, as presented above. Of these, copper and lead are known to be the earliest metals utilized by humans. Lead was used by humankind at least 5000 years ago (Settle and Patterson, 1980 Adriano, 1986). The production of these eight elements has increased considerably since the dawn of the industrial age in the 1850s (Table 9.1). 

Frankenberger W.T. Jr. Effects of trace elements on arsenic volatilization. Soil Bio Biochem 1997 30 269-274. 

Violante A, Krishnamurti GSR, Pigna M (2008) Mobility of trace elements in soil environments. In Violante A, Huang PM and Gadd G (eds) Wiley-JUPAC series on biophysico-chemical processes of metals and metalloids in soil environments. John Wiley Sons, Hoboken, USA Waltham AC, Eick MJ (2002) Kinetic of arsenic adsorption on goethite in the presence of sorbed silicic acid. Soil Sci Soc Am J 66 818-825 Waychunas GA, Fuller CC, Rea BA, Davis J (1996) Wide angle X-ray scattering (WAXS) study of two-line ferrihydrite structure Effect of arsenate sorption and counterion variation and comparison with EXAFS results. Geochim Cos-mochim Acta 60 1765-1781... 

Nakashima et al. [719] detail a procedure for preliminary concentration of 16 elements from coastal waters and deep seawater, based on their reductive precipitation by sodium tetrahydroborate, prior to determination by graphite-furnace AAS. Results obtained on two reference materials are tabulated. This was a simple, rapid, and accurate technique for determination of a wide range of trace elements, including hydride-forming elements such as arsenic, selenium, tin, bismuth, antimony, and tellurium. The advantages of this procedure over other methods are indicated. 

Kreppel, H., K. Kolb, F.X. Reichl, B. Fichtl, and W. Forth. 1988. Pretreatment with low doses of cadmium or zinc decreases lethality in mice acutely poisoned with arsenic. Pages 594-600 in Trace Element Analytical Chemistry in Medicine and Biology. Walter de Gruyter, Berhn. 

Ahn, J.S., H.T. Chon, and K.W. Kim. 1999. Arsenic and heavy metal contamination and uptake by rice crops around an abandoned Au-Ag mine in Korea. Pages 932-933 in W.W. Wenzel, D.C. Adriano, B. Alloway, H.E. Doner, C. Keller, N.W. Lepp, M. Mench, R. Naidu, and G.M. Pierzynski (eds.). Proceedings of the Fifth International Conference on the Biogeochemistry of Trace Elements, July 11-15, 1999, Vienna, Austria. 

Nixon277 compared atomic absorption spectroscopy, flame photometry, mass spectroscopy, and neutron activation analysis as methods for the determination of some 21 trace elements (<100 ppm) in hard dental tissue and dental plaque silver, aluminum, arsenic, gold, barium, chromium, copper, fluoride, iron, lithium, manganese, molybdenum, nickel, lead, rubidium, antimony, selenium, tin, strontium, vanadium, and zinc. Brunelle 278) also described procedures for the determination of about 20 elements in soil using a combination of atomic absorption spectroscopy and neutron activation analysis. 

Smedley, P.L., Zhang, M., Zhang, G., Luo, Z. 2003. Mobilisation of arsenic and other trace elements in fluviolacustrine aquifers of the Huhhot Basin, Inner Mongolia. Applied Geochemistry, 18, 1453-1477. 

We can see that the soluble and exchange forms of these metals are present in small amounts accounting merely for a few percent of the total metal content in soil. The content of organometal species is relatively high in the upper profile rich in humic species, whereas it drops sharply in the mineral horizons. Copper is extensively involved in the biogeochemical cycle in the Forest ecosystems and this is less profound for cobalt. It is noteworthy that a large part of metals (in particular, of copper) become bound to iron hydroxides. This is typical for various trace elements, including arsenic, zinc and other elements with variable valence. 

The technological information derived from a study of the early jettons can be summarized quite simply - before ca. AD 1450, European jettons contained on average around 4% tin and 1-2% lead, with a low zinc content, typically less than 10%. Traces of antimony, silver and arsenic are often present at 0.1- 02%. Nickel is very low, usually less than 0.05%. After AD 1450, the zinc content rises quickly to over 20%, with a corresponding fall in the lead (less than 1%) and tin (less than 0.2%). The trace elements are usually less than 0.1%, with the exception of nickel, present up to 0.5%. The combined copper plus zinc total is usually greater than 97%. 

Figure 9.8 Trace element profile along a single hair using LA-ICP-MS. The horizontal axis refers to the tracking time of the laser along the hair, which equates to distance, (a) shows lead along individual hairs from different depositional environments A is a modern sample, B is an experimentally buried modern sample, C is from a surface-exposed (8 months) forensic case, and D is an archaeological sample (died 1867). (b) shows arsenic from three of these same samples. There is clearly postdepositional uptake of both elements in the archaeological samples, and in these particular examples little evidence of lateral variation.

Lester et al. [24] have described a robotic system for the analysis of arsenic and selenium in human urine samples which demonstrates how robotics has been used to integrate sample preparations and instrument analysis of a biological matrix for trace elements. The robot is used to control the ashing, digestion, sample injection and operation of a hydride system and atomic absorption instrument, including the instrument calibration. The system, which routinely analyses both As and Se at ppb levels, is estimated to require only... 

Depending on type, uranium deposits exhibit characteristic primary alteration and trace element zoning patterns, the latter commonly including, but are not limited to, elements exhibiting changes in oxidation state such as vanadium, selenium, molybdenum, arsenic, cobalt, and nickel (Fig. 3). It can be shown that... 

For removing low levels of priority metal pollutants from wastewater, using ferric chloride has been shown to be an effective and economical method [41]. The ferric salt forms iron oxyhydroxide, an amorphous precipitate in the wastewater. Pollutants are adsorbed onto and trapped within this precipitate, which is then settled out, leaving a clear effluent. The equipment is identical to that for metal hydroxide precipitation. Trace elements such as arsenic, selenium, chromium, cadmium, and lead can be removed by this method at varying pH values. Alternative methods of metals removal include ion exchange, oxidation or reduction, reverse osmosis, and activated carbon. 

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