Cadmium natural sources

As a rule, simulations consider emissions of heavy metals from anthropogenic and natural sources, transport in the atmosphere and deposition to the underlying surface (Figure 6). It is assumed that lead and cadmium are transported in the atmosphere only as a part of aerosol particles. Besides, chemical transformations of these metals do not change removal properties of their particles-carriers. On the contrary, mercury enters the atmosphere in different physical and chemical forms and undergoes numerous transformations during its pathway in the atmosphere (Ilyn et al., 2002 2004 Ilyin and Travnikov, 2003). 

In terms of hazard to the life of sea organisms heavy metals are inferior only to pesticides. Every year the Black Sea receives 300 kg of mercury, 290 tons of cadmium, 400 tons of copper, 2200 tons of lead and 14200 tons of zinc from natural sources [4]. 

The metal composition of native MTs depends on the natural source and/or on the previous exposure of the organism to metals. The inducible MT-1 and MT-2 isoforms isolated from adult and fetal human livers contain mainly zinc, while those isolated from adult human kidney contain mainly cadmium with some copper or zinc. It may be noted that in higher organisms MTs are the sole proteins in which cadmium accumulates naturally. Both mammalian tissue specific forms MT-3 and MT-4 contain zinc and copper. In contrast to MTs from mammalian sources, in which zinc, cadmium, and copper can be simultaneously bound, yeast (53 aa) and fungal (25 aa) MTs contain exclusively copper. Specific binding of cadmium or copper to different tissue specific MT forms in vivo has been encoimtered in the snail Helix pomatia. ... 

Pongratz R, Heumann KG (1999) Production of methylated mercury, lead, and cadmium by marine bacteria as a significant natural source for atmospheric heavy metals in polar regions. Chemosphere 39 89-102... 

Volcanoes are an important source of trace metals to the atmosphere—for some species (e.g., arsenic, cadmium, copper, lead, and selenium) they may be the principal natural source (e.g., Nriagu, 1998). Measurements of fluxes are complicated because of rapid condensation of the vapor phases carrying the... 

Cadmium is widely distributed in the earth s crust at an average concentration of about 0.1-0.2 mg/kg and is commonly found in association with zinc. Volcanic activity is major natural source of cadmium release to the atmosphere. The annual global flux from this source has been estimated to be 820 tons. Deep sea volcanism is also a source of environmental cadmium release, but the role of this process in the global cadmium cycle remains to be quantified (OECD, 1994). About 10-15% of total airborne cadmium emissions arise from natural processes (WHO, 1992a). 

Cadmium deposited from the atmosphere onto soil can come from a variety of natural and anthropogenic sources (Alloway and Steinnes, 1999 McArthur, 2001). It is estimated that volcanoes, the dominant natural source of atmospheric Cd, emit 520 mg of Cd into the atmosphere aimually. The dominant anthropogenic source of emission of Cd into the atmosphere is primary non-ferrous metal production, which accounts for an estimated 4721 mg of Cd emitted into the atmosphere annually. The amount of Cd emitted into the atmosphere from all anthropogenic sources is estimated to be about one order of magnitude greater than that emitted from all natural sources. 

Exposure of humans to cadmium occurs both through the environment and occupational settings. Atmospheric emissions from man-made sources exceed those from natural sources by about one order of magnitude (Kazantzis 1986). 

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. 

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. 

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

Cadmium - the atomic number is 48 and the ehemical symbol is Cd. The name derives from the Greek kadmeia for calamine (zinc carbonate) with which it was found as an impurity in nature. Kadmeia was also the name of the fortress of Thebes, a city in the Boeottia region of central Greece. The fortress was named after its founder, Cadmus, who was the son of the Phoenician king, Agenor, and brother of Europ and would be a possible source for the name of the ore. The element was discovered and first isolated by the German physician Friedrich Stromeyer in 1817. 

Cadmium is found naturally deep in the subsurface in zinc, lead, and copper ores, in coal, shales, and other fossil fuels it also is released during volcanic activity. These deposits can serve as sources to ground and surface waters, especially when in contact with soft, acidic waters. Chloride, nitrate, and sulfate salts of cadmium are soluble, and sorption to soils is pH-dependent (increasing with alkalinity). Cadmium found in association with carbonate minerals, precipitated as stable solid compounds, or coprecipitated with hydrous iron oxides is less likely to be mobilized by resuspension of sediments or biological activity. Cadmium absorbed to mineral surfaces (e.g., clay) or organic materials is more easily bioaccumulated or released in a dissolved state when sediments are disturbed, such as during flooding. 

Only minute amounts of cadmium are found in natural waters in the United States. Hazardous waste discharges from the electroplating, photography, insecticide, and metallurgy industries can increase cadmium levels. Another common source of cadmium in drinking water is from... 

This practical exercise makes use of an istopically enriched cadmium standard which is available from a number of sources. However, any element with an enriched isotope can be used in place of cadmium, provided that the natural abundance is known. 

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