Biological availability metals

Campbell, P.G.C. et al. (1988) Biologically Available Metals in Sediments. Associate Committee on Scientific Criteria for Environmental Quality Report NRCC No. 27694, 298 p. Ottawa National Research Council Canada. 

Subgroup on Metals of the Tri-Academj Committee on Acid Deposition, Acid Deposition Effects on Geochemical Cjcling and Biological Availability of Trace Elements, National Academy Press, Washington, D.C., 1985. 

The destiny of most biological material produced in lakes is the permanent sediment. The question is how often its components can be re-used in new biomass formation before it becomes eventually buried in the deep sediments. Interestingly, much of the flux of phosphorus is held in iron(lll) hydroxide matrices and its re-use depends upon reduction of the metal to the iron(ll) form. The released phosphate is indeed biologically available to the organisms which make contact with it, so the significance attributed to solution events is understandable. It is not clear, however, just how well this phosphorus is used, for it generally remains isolated from the production sites in surface waters. Moreover, subsequent oxidation of the iron causes re-precipitation of the iron(lll) hydroxide floes, simultaneously scavenging much of the free phosphate. Curiously, deep lakes show almost no tendency to recycle phosphorus, whereas shallow... 

Other d-metals are also vital to health. For example, chromium(III) plays a role in the regulation of glucose metabolism. Copper(I) is an essential nutrient for healthy cells and is the only biologically available Lewis acid with a + 1 charge. 

Montgomery, J.R., M. Price, J. Thurston, G.L. de Castro, L.L. Cruz, and D.D. Zimmerman. 1978. Biological availability of pollutants to marine organisms. U.S. Environ. Protection Agen. Rep. 600/3-78-035. 134 pp. Mora, M.A. and D.W. Anderson. 1995. Selenium, boron, and heavy metals in birds from the Mexicali Valley, Baja California, Mexico. Bull. Environ. Contamin. Toxicol. 54 198-206. 

Most metals, for which compounds are carcinogenic, are from IV group of Periodic Table of Elements. In biological systems, carcinogenic metals can form stable complexes and biological availability of these complexes determines the carcinogenic potential of various metal compounds. 

The structures show the lone pairs of electrons that form bonds with metal cations. Both chelates and siderophores hold micronutrient cations in solution and in a biologically available form until the cations can be used by the... 

Biological extractions are carried out to determine if biologically important elements are at levels that are sufficient, yet not toxic, for plant needs. Acid soil extraction to determine the biologically available plant nutrients is the most common type of extraction of soil carried out. The objective is to extract a portion, not all, of a particular nutrient or metal that is correlated to the amount available to plants. The plants of primary interest are crop plants such... 

In some cases, resins have been used to try to determine only the plant or more generally the biological availability of an ionic species. Resins placed in soil have also been used to study ion speciation, soil microbiology, various phosphorus measurements, soil nutrient supply rate, nutrient transformations and movement, and micronutrient and metal toxicity [22-25],... 

Complexation by organic matter causes a wide variety of effects on the bioavailability of metals. As noted earlier, the toxicity of dissolved copper can be reduced by complexation with organic matter. In this case, complexed copper is not biologically available to phytoplankton. The other extreme is exhibited by iron, in which the metal s bioavailability is enhanced by complexation with organic matter. There are two likely... 

Metals cannot be created or destroyed, but can change form, altering their biological availability and toxicity. Metallic mercury evaporates and is redistributed... 

Several elements, particularly zinc and copper, could play a role as trace nutrients for phytoplankton. They are known to be important for growth of terrestrial plants, but neither the requirement for these nutrients nor the elemental distributions in seawater are well known. The biological availability of both zinc and copper is controlled by their complexation with organic material. Analytical methods that have the distinction of being able to discriminate chemical forms of the metal are needed. These measurements reflect the chemical reactivity and biological availability or toxicity of the metal more accurately. 

Thompson EA, Luoma SN, Johansson CE, et al. 1984. Comparison of sediments and organisms in identifying sources of biologically available trace metal contamination. Water Research 18 755-766. 

The simple definition of biological availability as the fraction of the total trace metal available for uptake by the biota implicitly assumes that all relevant organisms will have similar uptake characteristics. In addition the use of biological availability as a chemical parameter involves the assumption that it can be identified with particular chemical species or groups of species. Perhaps surprisingly many of the studies carried out to date have lent support to these assumptions, though the detailed mechanisms of the uptake processes remain unclear. Some of the inorganic chemical species identified as... 

A further group of biologically available chemical species comprises organic compounds of the trace elements, which may be divided into two groups organic complexes of cations, and metal and non-metal alkyls (Table 3). These species are mainly neutral molecules, in contrast to the ionic species identified in Table 2, and are thought to be taken up as a consequence of their lipid-solubility (Florence et al., 1983). 

Toxic ligands (CO, NO, CN, F , H2S) can bind to metals in the active site of enzymes, thus inhibiting substrate binding, or coordinate to more readily available metal ions, thereby blocking the proper biological function of the metal. However, recent research suggests that such molecules are essential to several hydrogenases (see Chapters 8 and 9). 

The pattern of soil pollution correlate strongly with contamination of the plants. The metals in the soils of the investigated territories are highly biologically available. 

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