Chromium environmental chemistry

S. A. Katz and H. Salem, The Biological and Environmental Chemistry of Chromium, VCH, Weinheim, 1994, 214pp. 

Lee T, Tera F (1986) The meteoritic chromium isotopic composition and limits for radioactive Mn in the early solar system. Geochim Cosmochim Acta 50(2) 199-206 Lemly AD (1985) Toxicology of selenium in a freshwater reservoir Implications for environmental hazard evaluation and safety. Ecotoxicol Environ Saf 10 314-338 Lemly AD (1998) Pathology of Selenium Poisoning in Fish. In Environmental Chemistry of Selenium. 

The term heavy metal in environmental chemistry has traditionally been used to describe certain elements and compounds that are hazardous to the health of humans and other animals. Some elements included in this definition are arsenic, beryllium, cadmium, chromium, lead, and mercury. 

Merian E. 1984. Introduction on environmental chemistry and global cycles of chromium, nickel, cobalt, beryllium, arsenic, cadmium and selenium, and their derivatives. Toxicol Environ Chem 8 9-38. 

Krishnamurthy S. and Wilkens M. M. (1994) Environmental chemistry of chromium. Northeastern Geol. 16, 14-17. 

Meeian E (1985) Introduction on Environmental Chemistry and Global Cycles of Chromium, Nickel, Cobalt, Beryllium, Arsenic, Cadmium, and Selenium. In Merian E, Erei RW, Haerdi W and Schlatter C, eds. Carcinogenic and Mutagenic Compounds, pp. 25-32. Gordon Breach, London. 

Naptbol, l-(2-carboxyphenyla2o)-chromium complex geometrical isomerism, 68 Neptunium breeder reactor fuels Purex process, 955 reprocessing, 954 electrolytic reduction Purex process, 949 environmental chemistry, 961 extraction Purex process, 951 Purex process, 946,950 recovery... 

Chromium can exist in several oxidation states from Cr(0), the metallic form, to Cr(Vl). The most stable oxidation states of chromium in the environment are Cr(lll) and Cr(Vl). Besides the elemental metallic form, which is extensively used in alloys, chromium has three important valence forms. The trivalent chromic (Cr(lll)) and the tetravalent dichromate (Cr(Vl)) are the most important forms in the environmental chemistry of soils and waters. The presence of chromium (Cr(Vl)) is of particular importance because in this oxidation state Cr is water soluble and extremely toxic. The solubility and potential toxicity of chromium that enters wetlands and aquatic systems are governed to a large extent by the oxidation-reduction reactions. In addition to the oxidation status of the chromium ions, a variety of soil/sediment biogeochemical processes such as redox reactions, precipitation, sorption, and complexation to organic ligands can determine the fate of chromium entering a wetland environment. 

Katz SA (1998) Chromium, environmental analytical chemistry. In Meyers RA (ed.) Encyclopedia of Environmental Analysis and Remediation, pp. 1129-1141. New York Wiley. 

The importance of toxic elements in environmental chemistry is rarely questioned, but a relatively small number of elements (mercury, lead, and cadmium) have received a large share of researchers attention. The environmental chemistry of the transition metals, e.g., chromium, nickel, manganese, cobalt, copper, etc., has also been investigated principally because of their roles in metabolism, especially enzymatic processes. However, two non-metals, arsenic and selenium, and two metals, beryllium and vanadium, are elements which will become more significant in the future from environmental and toxicological points of view. Arsenic and selenium have been investigated, but much more work is needed because of the importance of these two elements in the environment. The author considers beryllium and vanadium to be problem metals of the future . The primary exposure route for both beryllium and vanadium is via the atmosphere and as lower environmental standards are imposed, more uses are found for each element, and more fossil fuels (source of V) are burned, the amounts added to the atmosphere will have more significance. 

Selenium (masses 74, 76, 77, 78, 80, and 82 Table 1) and chromium (masses 50, 52, 53 54 Table 1) are treated together in this chapter because of their geochemical similarities and similar isotope systematics. Both of these elements are important contaminants in surface and ground water. They are redox-active and their mobility and environmental impact depend strongly on valence state and redox transformations. Isotope ratio shifts occur primarily during oxyanion reduction reactions, and the isotope ratios should serve as indicators of those reactions. In addition to environmental applications, we expect that there will be geological applications for Se and Cr isotope measurements. The redox properties of Se and Cr make them promising candidates as recorders of marine chemistry and paleoredox conditions. 

Peterson, M.L. Brown Jr., G.E. Parks, G.A. (1997) Quantitative determination of chromium valence in environmental samples using XAFS spectroscopy. In Voigt, J.A. Bunker, B.C. Casey,W.H. Wood,T.E. Crossey, L.J. (eds.) Aqueous chemistry and geochemistry of oxides, oxyhydroxides, and related materials. Materials Research Society, Pittsburgh... 

A redox titration is based on an oxidation-reduction reaction between analyte and titrant. In addition to the many common analytes in chemistry, biology, and environmental and materials science thai can be measured by redox titrations, exotic oxidation states of elements in uncommon materials such as superconductors and laser materials are measured by redox titrations. For example, chromium added to laser crystals to increase their efficiency is found in the common oxidation states +3 and +6, and the unusual +4 state. A redox titration is a good way to unravel the nature of this complex mixture of chromium ions. 

Barnhart J. 1997. Chromium chemistry and implications for environmental fate and toxicity. Journal of Soil Contamination 6(6) 561-568. 

Beyersmann D, Koster A, Buttner B. 1985. Model reactions of chromium compounds with mammalian and bacterial cells. In MerianE, Fre RW, Hardi W, et al., eds. Carcinogenic and mutagenic metal compounds Environmental and analytical chemistry and biological effects. London, UK Gordon and Breach Science Publishers, 303-310. 

Crumbie, R. L. Environmentally Responsible Redox Chemistry An Example of Convenient Oxidation Methodology without Chromium Waste, J. Chem. Educ. 2006, 83, 268-269. 

Due to increasing environmental problems, the use of metal catalysts will gradually be reduced in the future the reduction in the early use of lead- and chromium-based catalysts is evidence of this. With stricter regulations governing the release of metals, the cost of catalyst recovery and environmental remediation is quickly making noncatalytic processes for the production of carboxylic acids preferable. Coupled with recent advances in the field of biocatalysis, metal-mediated oxidations may give way to alternative processes as we enter a new millennium of chemistry. 

Greene, J.C., Miller, W.E., Debacon, M., Long, M.A. and Bartels, C.L. (1988) Use of Selenas-trum capricornatum to assess the toxicity potential of surface and groundwater contamination caused by chromium waste. Environmental Toxicology and Chemistry, 7, 35-39. 

Chromium in Soil Perspectives in Chemistry, Health, and Environmental Regulation, D. M. Proctor, B. L. Finley, M. A. Harris, D. J. Paustenbach, and D. Rabbe, Eds., Lewis Publishers, Boca Raton, FL, 1997. 

Since the beginning of the twenty-first century, the organic chemistry of hypervalent iodine compounds has experienced an unprecedented, explosive development. Hypervalent iodine reagents are now commonly used in organic synthesis as efficient multipurpose reagents whose chemical properties are similar to derivatives of mercury, thallium, lead, osmium, chromium and other metals, but without the toxicity and environmental problems of these heavy metal congeners. One of the most impressive recent achievements in the field of iodine chemistry has been the discovery of hypervalent iodine catalysis. 

Advantageously, this reaction utilises a low-valent chromium complex, which reduces the catalyst s toxicity. Furthermore, this reaction proceeds without the need for a cocatalyst and at ambient pressure and temperature. From a green chemistry standpoint, these conditions are favourable and economically and environmentally feasible. This method also delivers safer reaction conditions and provides a sustainable means of trimerising ethane, completely by eliminating the use of a cocatalyst, which can cause difficulty in intermediate isolation or spectroscopic detection. 

---