Toxic Trace Elements

Sediment Analysis. Sediment is the most chemically and biologically active component of the aquatic environment. Benthic invertebrate and microbial life concentrate in the sediment, a natural sink for precipitated metal forms, and an excellent sorbent for many metal species. TTie extent to which potentially toxic trace element forms bind to sediment is determined by the sediment s binding intensity and capacity and various solution parameters, as well as the concentration and nature of the metal forms of interest. Under some conditions sediment analyses can readily indicate sources of discharged trace elements. 

The following chapter is a case study of how the three problem areas illustrated (dissolved oxygen depletion, erosion/deposition, and potentially toxic trace elements) may be successfully addressed on a major river system using quantitative, semi-quantitative and qualitative approaches respectively. 

The goals of this chapter do not include a "state of the art" literature review which would be appropriate for a more in-depth discussion of one particular problem area. Rather the intent is to illustrate mechanistic approaches to river quality assessment using the three globally relevant water quality problem areas discussed in the previous chapter dissolved oxygen depletion, erosion/deposition, and potentially toxic trace elements. The information provided does not include all rationale, methology or approaches used in the study as this is beyond the scope of the chapter. Additional general information on application of the intensive river quality assessment approach in the Willamette River basin may be found elsewhere (4-9, 11-14, 17). 

Potentially Toxic Trace Elements - A Qualitative Approach... 

Methods. As discussed in the previous chapter, a number of approaches have been used to assess the presence of potentially toxic trace elements in water. The approaches used in this assessment include comparative media evaluation, a human health and aquatic life guidelines assessment, a mass balance evaluation, probability plots, and toxicity bioassays. Concentrations of trace elements were determined by atomic absorption spectrometry according to standard methods (21,22) by the Oregon State Department of Environmental Quality and the U.S. Geological Survey. 

Comparative Media Evaluation. Table 4 is a summary of trace element occurrences for water, sediment, fish and rocks in Oregon as compared with concentrations measured elsewhere in the world. Details of the comparison parameters are provided in the footnotes to Table 4. The table indicates that no excessively high concentrations of potentially toxic trace elements exist in Willamette River water relative to "uncontaminated sites. 

Jenkins DW. 1981. Biological monitoring of toxic trace elements, Vol 1, Biological monitoring and surveillance Vol 2, Toxic hace metals in plants and animals of the world, Parts I, II, and III. U.S. Environmental Protection Agency, Envhonmental Systems Laboratory EPA-600/S3-80-090. 

Caroli S, Forte G, Iamiceu AL, Galoppi B 1999) Determination of essential and potentially toxic trace elements in honey by inductively coupled plasma-based techniques. Talanta 50 327-336. Chiswell B, Johnson D (1994) Manganese. In Seiler HG, Sigel A, Sigel H, eds. Handbook on metals in clinical and analytical chemistry. Dekker, New York. 

Hoadley, J.E. and R.J. Cousins. 1988. Regulatory mechanisms for intestinal transport of zinc and copper. Pages 141-155 in A.S. Prasad (ed.). Essential and Toxic Trace Elements in Human Health and Disease. Alan R. Liss, NY. 

Schroeder WH, Dobson M, Kane DM, et al. 1987. Toxic trace elements associated with airborne particulate matter A review. J Air Pollut Control Assoc 37 1267-1285. 

Table 8.10 shows the concentration range of potential toxic trace elements in U.S. sewage sludges, as summarized by Chaney (1989). In this table, data on maximum concentration of toxic trace elements in dry, digested sewage sludges are compared to concentrations of the elements in median sludges and in soils. The subsurface contamination that may result from uncontrolled disposal on land surfaces... 

Schroeder, W. H., M. Dobson, D. M. Kane, and N. D. Johnson, Toxic Trace Elements Associated with Airborne Particulate Matter A Review, J. Air Pollut. Control Assoc., 37, 1267-1285 (1987). 

Linton, R. W., Williams, P., Evans, C. A. Natusch, D. R. S. 1977. Determination of the surface predominance of toxic trace elements in airborne particles by ion microprobe mass spectrometry and Auger electron spectroscopy. Analytical Chemistry, 49, 1514-1521. 

Natusch, D. F. S., Wallasce, J. R. Evans, C. A. 1974. Toxic trace elements Preferential concentration in respirable particles. Science, 183, 202-204. 

The environmental risk leachates from the retort residue represent on the ecosystem is not only related to the absolute content of various potentially toxic trace elements in the semicoke, which in most cases may not be significantly higher than the content of the natural oil shales. It also depends on the leachability of these elements when the residue comes in contact with water, and on the elemental speciation. Important factors to consider in this context are ... 

Preliminary studies have shown that it is possible to remove over half of the potentially toxic trace elements present in coal when the mineral matter is reduced by coal washing. When coal is burned in a power plant, about 13% of the mercury and about 50% of the lead and cadmium may remain with the fly ash. Analytical chemical techniques have been developed to determine Hg, Cu, Cr, Mn, Ni, Cd, Pb, and F in coal and fly ash. These techniques produce accurate and precise results despite the fact that there are no coals with established trace element content, except for mercury. 

The second program, funded by the U.S. Bureau of Mines, is concerned with the fate of the various toxic trace elements present when coal is burned in power plants. Coals and ashes from experimental combustors and power plants are collected and chemically analyzed. Comparing the amount of a trace element in a coal with the amount found in the ash resulting from the combustion of that coal allows us to determine the maximum amount of that element that could be emitted into the environment via the power plant stacks. 

Feng, X., Hong, Y., Hong, B. and Ni, J. (2000) Mobility of some potentially toxic trace elements in the coal of Guizhou, China. Environmental Geology, 39(3-4), 372-77. 

Sweet CW, Vermette SJ. 1993. Sources of toxic trace elements in urban air in Illinois. Environ Sci Technol 27 2502-2510. 

Riedel, GF., Sanders, J.G, and Breitburg, D.L. (2003) Seasonal variability in response of estuarine phytoplankton to stress linkages between toxic trace elements and nutrient enrichment. Estuaries 26, 323-338. 

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