Trace elements environmental impacts

Keywords Lake, sediment, geochemistry, palaeolimnology. trace elements, environmental change, human impact... 

As both elements are important environmental contaminants whose mobility and environmental impact depend on redox reactions, we expect that Cr and Se isotope analyses will be used widely as indicators of oxyanion reduction. It may also be possible to trace the origin of the Se or Cr via isotopic signatures, but only if the possible confounding effects of reduction can be constrained. 

Bargagli, R., Cateni, D., Nelli, L., Olmastroni, S. Zagarese, B. 1997. Environmental impact of trace element emissions from geothermal power plants. Archives of Environmental Contamination and Toxicology, 33, 172-181. 

The coal service laboratory, which in the past was concerned with determining the ASTM Procedures for Ultimate and Proximate Analysis, is now responsible for analyzing trace elements in coal. With this sort of facility and technical skill in mind, our own wet chemical laboratory devised relatively routine procedures for determining trace elements in coal that could have an undesirable environmental impact including Hg, Be, Se, As, Cd, Pb, F, Cu, Ni, Zn, Cr, Te, Ge, Mn, Sn, B, Bi, Sb, V, Li, Co, and Ag. 

The paucity of available information on the biological consequences of coal use emissions has been underlined recently by Dixie Lee Ray (8) in her energy report to the President and during a conference sponsored jointly by the American Academy of Pediatrics and the Committee on Environmental Hazards (9). The lag in knowledge of coal-related trace element emissions and their environmental impact has been attributed in large part to belated federal funding (10, 11). 

Information on the element and mineral content of coals provides only a partial picture of the potential behavior of the trace elements in coal. The picture can be brought into sharper focus if we know an element s mode of occurrence (chemical form). The mode of occurrence of an element in coal determines its technological behavior, environmental impact, and economic potential, and provides insight into the geochemical processes that occurred during coalihcation. 

According to Styron et al., (1979) for a realistic assessment of the magnitude of release of radionuclides, special attention needs to be given to lead-210 and polonium-210 since they appear to have a large potential for significant environmental impact and have not received sufficient attention in trace-element studies for power plants. Another potentially important parameter in determining radiation exposure to man centres on disposal and utilization of coal ash and refuse. Lee et al., (1977) have suggested that emanation of radon-222 from ash disposal ponds will be the most serious radionuclide problem associated with increased use of coal. A potential hazard can be associated with the use of fly ash in cement and concrete blocks and in roadway construction. The radium-226 in these concrete blocks used for home construction may constitute an important source of radon-222 dose to the public. 

Some elements commonly occur in ores of other elements and so can become problems, even where they are present at ultratrace levels. These elements can have deleterious or beneficial effects upon the properties of the major element that is won from the ore. The impact of trace elements on properties of materials, even when they are present at ultratrace concentrations, can be striking, and understanding their influence on materials is important. Regulations, either environmental or prescriptive, will continue to have a major impact on our interest in trace elements. 

Future trends in trace element analysis will put even greater pressure on the need to provide unbiased determinations. Increasing interest in the role of trace elements in health and disease will provide the stimulus for the better provision of quantitative determinations on which important decisions are made (Centers for Disease Control, 1991 Moukarzel et al., 1992). Increased public awareness and legislation are likely to bring about substantial reductions in the currently acceptable levels of occupational and environmental exposure to some non-essential elements such as lead, cadmium and aluminium. Determinations that are made as part of the assessment of such exposure will need to be both carefully validated and reproducible over many years or decades (Braithwaite and Brown, 1988 Brown, 1991), which will have a serious impact on laboratory costs. However, reproducible trace element determination with a low bias in biological fluids represents the cornerstone of any proper understanding of the role of trace elements in human health and disease. 

This chapter is devoted to situations in which trace elements are found as natural contaminants, in concentrations which considerably exceed natural background values discussed above. Such situations are typical for areas rich in metal ore deposits. Their potential environmental impact depends on their location within a catchment. If they are situated in the upper part, a large area and many different environmental compartments will be affected (Fig. 13). Local contamination of soils, plants, sediments and water occurs almost in every case, the degree to which a whole catchment is affected by contaminated waters and glacial or alluvial sediments depends on the size of the ore deposit, the slope and the climate of a given area. 

An analysis of coal ash may also be carried out to determine not only the composition of coal ash but also the levels at which trace elements occur in ash. These data are useful for environmental impact modeling, and may be obtained by spectroscopic methods such as inductively coupled plasma (ICP) or atomic absorption spectroscopy (AAS). 

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