Cadmium sources

Synthesis of CdSe Quantum Dots from Cadmium Sources Other Than Dimethyl Cadmium... 

Munger, C., Hare, L. and Tessier, A. (1999). Cadmium sources and exchange rates for Chaoborus larvae in nature, Limnol. Oceanogr., 44, 1763-1771. 

Roy, I. and Hare, L. (1999). Relative importance of water and food as cadmium sources to the predatory insect Sialis velata (Magaloptera), Can. J. Fish. Aquat. Sci., 56, 1143-1149. 

Apparently, the first such experiment was done by Moore, Wulf, and Badger,318 who used the cadmium source with a NaCl filter to remove wavelengths below 2050 A. They monitored N203, which is an end product of the reaction, and is formed by the addition of NO to the product NOa. Recently, Basco, Callear, and Norrish22 reported that no product formation occurs when only the ground vibrational level of A2H + exists. If their observation is correct, then all the decomposition must come from the first vibrational level. It is difficult to believe that this relatively small amount of additional energy could have such a profound effect. 

Most of these fixed-wavelength detectors can be filtered with a series of filters and or phosphors to detect at wavelengths varying from 280 to 546 nm. Wavelengths in the range 214-229 nm can be monitored by the use of zinc and cadmium source lamps, respectively [46]. 

Other cadmium sources can include solder, galvanized pipes and metal fittings, pollution from disposal of cadmium-containing materials and from mining operations (see Chapter 7). However, concentrations of cadmium in drinking-water above the guideline value are unusual. 

Figure 4 Seawater cadmium reconstructed from foraminifera using a depth-dependent empirical distribution coefficient versus estimated bottom-water cadmium (sources Boyle, 1988, 1992).

Figure 1 Relative importance of the various cadmium sources to human exposure.

Kazantzis G (1986) Cadmium sources, exposure and possible carcinogenicity. In O Neill IK, Schuller P, Fishbein L (eds) Environmental carcinogens selected methods of analysis, vol 8. I ARC, Lyon, France, pp 93-100 Kazantzis G (1987) Cadmium. In Fishbein L, Furst A, Mehlman MA (eds) Advances in modern toxicology, vol XL Princeton Scientific, Princeton, NJ, pp 127-143... 

Figure 19.3 Labelling of batteries containing cadmium. Source BattV.

Uranium, not as rare as once thought, is now considered to be more plentiful than mercury, antimony, silver, or cadmium, and is about as abundant as molybdenum or arsenic. It occurs in numerous minerals such as pitchblende, uraninite, carnotite, autunite, uranophane, and tobernite. It is also found in phosphate rock, lignite, monazite sands, and can be recovered commercially from these sources. 

Typically, soHd stabilizers utilize natural saturated fatty acid ligands with chain lengths of Cg—C g. Ziac stearate [557-05-1/, ziac neodecanoate [27253-29-8] calcium stearate [1592-23-0] barium stearate [6865-35-6] and cadmium laurate [2605-44-9] are some examples. To complete the package, the soHd products also contain other soHd additives such as polyols, antioxidants, and lubricants. Liquid stabilizers can make use of metal soaps of oleic acid, tall oil acids, 2-ethyl-hexanoic acid, octylphenol, and nonylphenol. Barium bis(nonylphenate) [41157-58-8] ziac 2-ethyIhexanoate [136-53-8], cadmium 2-ethyIhexanoate [2420-98-6], and overbased barium tallate [68855-79-8] are normally used ia the Hquid formulations along with solubilizers such as plasticizers, phosphites, and/or epoxidized oils. The majority of the Hquid barium—cadmium formulations rely on barium nonylphenate as the source of that metal. There are even some mixed metal stabilizers suppHed as pastes. The U.S. FDA approved calcium—zinc stabilizers are good examples because they contain a mixture of calcium stearate and ziac stearate suspended ia epoxidized soya oil. Table 4 shows examples of typical mixed metal stabilizers. 

Batteries. Many batteries intended for household use contain mercury or mercury compounds. In the form of red mercuric oxide [21908-53-2] mercury is the cathode material in the mercury—cadmium, mercury—indium—bismuth, and mercury—zinc batteries. In all other mercury batteries, the mercury is amalgamated with the zinc [7440-66-6] anode to deter corrosion and inhibit hydrogen build-up that can cause cell mpture and fire. Discarded batteries represent a primary source of mercury for release into the environment. This industry has been under intense pressure to reduce the amounts of mercury in batteries. Although battery sales have increased greatly, the battery industry has aimounced that reduction in mercury content of batteries has been made and further reductions are expected (3). In fact, by 1992, the battery industry had lowered the mercury content of batteries to 0.025 wt % (3). Use of mercury in film pack batteries for instant cameras was reportedly discontinued in 1988 (3). 

Lasers act as sources and sometimes as amplifiers of coherent k—uv radiation. Excitation in lasers is provided by external particle or photon pump sources. The high energy densities requked to create inverted populations often involve plasma formation. Certain plasmas, eg, cadmium, are produced by small electric discharges, which act as laser sources and amplifiers (77). Efforts that were dkected to the improvement of the energy conversion efficiencies at longer wavelengths and the demonstration of an x-ray laser in plasma media were successful (78). 

Naturally occurring cadmium compounds are limited to the rare minerals, greenockite [1317-58 ] CdS, and otavite (1), an oxycarbonate, but neither is an economically important source of cadmium metal or its compounds. Instead, cadmium compounds are more usually derived from metallic cadmium [7440-43-9] which is produced as a by-product of lead—2inc smelting or electrolysis (see Cadmiumand cadmium alloys). Typically, this cadmium metal is burnt as a vapor, to produce the brown-black cadmium oxide [1306-19-0], CdO, which then acts as a convenient starting material for most of the economically important compounds. 

Dimethylcadmium has found use as a volatile source of Cd for metal organic chemical vapor deposition (MOCVD) production of cadmium-containing semiconductor thin films (qv) such as CdS, Cdi 2 Hg -Te, or Cdi 2 Mn -Te, as multiple quantum weU species (32). Semiconductor-grade material seUs for... 

This method is used for the determination of total chromium (Cr), cadmium (Cd), arsenic (As), nickel (Ni), manganese (Mn), beiylhum (Be), copper (Cu), zinc (Zn), lead (Pb), selenium (Se), phosphorus (P), thalhum (Tl), silver (Ag), antimony (Sb), barium (Ba), and mer-cuiy (Hg) stack emissions from stationaiy sources. This method may also be used for the determination of particulate emissions fohowing the procedures and precautions described. However, modifications to the sample recoveiy and analysis procedures described in the method for the purpose of determining particulate emissions may potentially impacl the front-half mercury determination. 

It is also clear that it is difficult to relate cause and effect to any specific chemical since, with the exception of point source effluents, many waterways contain a multitude of chemicals, of which the active endocrine disruptor may not be that which has been measured in the water or tissue. For such reasons, many studies have used in vitro experiments in which isolated tissue, either from a control animal or one captured in a polluted water system, is exposed to a single pollutant in the laboratory. Such experiments have shown significant disruption to testicular activity by a wide range of xenobiotics, including cadmium, lindane, DDT, cythion, hexadrin and PCBs. ... 

Other Considerations The fine fraction of PM emissions from a combustion source often contains cadmium and other metals. Use of a condensation scrubber to capture fine PM may provide an effective method of reducing the emission of metals. 

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