Biological and environmental significance

Nickel occurs as a cofactor in four enzymes known to date (Walsh and Orme-Johnson, 1987). Ureases from plant and animal sources use two Ni atoms as Lewis acids, a role more typical of Zn. In the other three enzymes, all bacterial. Ni is redox active. In methyl coenzyme M reductase of methanogenic bacteria, Ni is found in a tetrapyrrole (factor F430) and cycles between Ni(ll) and Ni(l). Many bacteria contain Ni-dependent hydroge-nase(s) and methanogenic and acetogenic bacteria have a specific Ni-containing CO 

Biological monitoring is mainly carried out for acute exposures in the workplace, and most typically Involves urine and serum collection. Although the NI content of these fluids does not in general Indicate specific health risks, biological tolerance values of 30 g Ni/L in urine and 8/ g Ni/L in serum have been recommended (Sunderman Jr., 1988). These values are at least and order of magnitude higher than those found in individuals without specific sources of excessive exposure. 

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The most fundamental process dealing with the activation of C02 involves the hydration of C02 to produce bicarbonate and the reverse dehydration of bicarbonate to produce C02. These processes are of biological and environmental significance since they control the transport and equilibrium behavior of C02. The spontaneous hydration of C02 and dehydration of HCO3 are processes that are too slow and must therefore be catalyzed by metal complexes in order to expedite the overall conversion rate. In biological systems, a series of enzymes, the carbonic anhydrases, are the efficient catalysts and can accelerate the reactions by up to 7 orders of magnitude. The mechanism of this... 

The solubility of a gas in a mixture of solvents is a problem of interest in many industrial applications. One example is the removal of acidic compounds from industrial and natural gases. The solubility of a gas in a binary mixture containing water has particular importance because it is connected with the solubility of gases in blood, seawater, rainwater, and many other aqueous solutions of biological and environmental significance. Therefore, it is important to be able to predict the gas solubility in a mixture in terms of the solvent composition and the solubilities in the individual constituents of the solvent or in one pure component and a selected composition of the mixed solvent. 

There are a number of trends that will continue to influence future RM activity and a number of areas which are not yet very significant that will become more so. One important source of information on developments in the area of RMs is the series of International Symposia on Biological and Environmental Reference Materials (BERM), organization of which was described in Chapter 8. The Proceedings of these successive BERM Symposia have given a series of detailed snapshots of activity on a 2-3 year cycle over nearly two decades (BRM-i 1985 - BERM-7 99 )- Most of the information and projections in this Chapter are taken from various papers published in these BERM proceedings. 

Hatton A, Darroch L, Malin G (2004) The role of dimethylsulphoxide in the marine biogeochemi-cal cycle of dimethylsulphide. Oceanogr Mar Biol Ann Rev 42 29-56 Hatton A, Malin G, Turner S, Liss P (1996) DMSO a significant compound in the biogeochemical cycle ofDMS. In Kiene RP, Visscher P, Keller M, Kirst GO (eds) Biological and environmental chemistry of DMSP and related sulfonium compounds. Plenum, New York, pp 405—413... 

Nieboer, E. Richardson, D. H. S. 1980. The replacement of the nondescript term heavy metal by a biologically and chemically significant classification of metal ions. Environmental Pollution (Ser. B), 1, 3-26. 

The following methods are used for the quantitative analysis of copper in biological and environmental samples. It should be noted that the collection and treatment of samples require particular attention, and that the composition of the biological matrix may significantly affect the results. 

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