Bioaccumulation of trace elements

The biomethylation of metals and metalloids in soils and sediments appears to be a widespread phenomenon. Owing to their altered physical properties like volatility and lipid solubility, the methylated compounds are important in the mobilization, transport, and bioaccumulation of trace elements in the environment. The methylation of Cr(II) by methyl-cobalamine appears to proceed by a homolytic pathway involving the transfer of a methyl radical. CH3Cr(H203) is the product of this reaction, but is rapidly cleaved under acidic conditions to give methane and Cr(III). 

Wang, W.X., N.S. Fisher, and S.N. Luoma. 1996. Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis. Mar. Ecol. Prog. Ser. 140 91-113. 

Wang, D., G. Alfthan, A. Aro, A. Makela, S. Knuuttila, and T. Fiammar. 1995. The impact of selenium supplemented fertilization on selenium in lake ecosystems in Finland. Agricul. Ecosys. Environ. 54 137-148. Wang, W.X., N.S. Fisher, and S.N. Luoma. 1996. Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis. Mar. Ecol. Prog. Ser. 140 91-113. 

Hildebrand SG, Cushman RM, Carter JA. 1976. The potential toxicity and bioaccumulation in aquatic systems of trace elements present in aqueous coal conversion effluents. Proc Univ MO Annu Conf Trace Subst Environ Health. 10 305- 313. 

The appropriate interfacing of chemical with biologic and hydrologic models is a rather difficult problem. For example, the prediction of trace-element bioaccumulation by phytoplankton may require in some instances that the uptake rates and the compartmentalized loss rates for various solute species of the element present in the system be known. The effect, if any, on compartmentalized loss rates of the particular solute species taken up (e.g. HgCH3" " vs Hg " ") also needs to be known. The interaction effect of the concentration of one element upon the uptake and loss rates of another element, such as Hg on Se (33, 34, 35), also need to be known. In many instances, hydrodynamic models may have to be linked with,or otherwise incorporated, into the biologic and chemical models to permit predictions of, for example, increased trace-element levels in oysters resulting from increased anthropogenic inputs to an estuary. 

Monaci et al. (1997) performed a lichen-biomonitoring study in Siena by means of two different methods. The pattern of air quality in the study area was examined on the basis of the in situ frequency of different species of epiphytic lichens, i.e. using their species-specific sensitivity to the complex mixture of phytotoxic pollutants in the urban environment. The distribution of trace elements was evaluated quantitatively by an analysis of thalli of a tolerant species, P. caperata, known to be a reliable bioaccumulator of persistent atmospheric pollutants. The values obtained for Al, Ba, Cr, Cu, Fe, Pb and S were significantly higher in Sienese lichens over and above controls. Traffic was found to be the major source of atmospheric pollution. The pattern of trace-elemental deposition did not always coincide with air quality. lAP values were found to reflect essentially the emission of gaseous phytotoxic pollutants in the urban environment. 

Devineau, J. and C. Amiard Triquet 1985. Patterns of bioaccumulation of an essential trace element (zinc) and a pollutant metal (cadmium) in larvae of the prawn Palaemon serratus. Mar. Biol. 86 139-143. Dib, A., J.P Clavel, and J.P. Carreau. 1989. Effects of gamma-linolenic acid supplementation on lipid composition of liver microsomal membranes. I. Pregnant rats fed a zinc-deficient diet and those fed a balanced one. Jour. Clin. Biochem. Nutr. 6 95-102. 

Bertine, K.K. and E.D. Goldberg. 1972. Trace elements in clams, mussels, and shrimp. Limnol. Ocean. 17 877-884. Besser, J.M., T.J. Canfield, and T.W. La Point. 1993. Bioaccumulation of organic and inorganic selenium in a laboratory food chain. Environ. Toxicol. Chem. 12 57-72. 

Murphy, C.P. 1981. Bioaccumulation and toxicity of heavy metals and related trace elements. Jour. Water Pollut. Control Fed. 53 993-999. 

The preceding discussion demonstrates that in order to understand the role(s) of mass transfer with respect to trace element bioaccumulation, the following considerations must be examined ... 

The results of sequential leaching experiments and the bioaccumulation studies reveal a selective assimilation of certain chemical forms of some trace metals by molluscs. There seems to be a relationship between seawater-soluble chromium levels and accumulation of the element in the kidneys of exposed bivalves. Particulate forms of chromium, while present in the digestive glands, do not appear to have been assimilated by the organisms, even though much of the total chromium was dissolved by a relatively mild extractant -25% acetic acid. Thus, an estimation of the bioavailability of particulate metals based on their solubility in dilute acetic acid can be erroneously high, at least for herbivorous filter feeders. 

The natural global bio-geochemical cycling of mercury is characterized by degassing of the element from soils and surface waters, followed by atmospheric transport, deposition of mercury back to land and surface waters, and sorption of the compound to soil or sediment particulates. Mercury deposited on land and open water is in part revolatilized back into the atmosphere. This emission, deposition, and revolatilization creates difficulties in tracing the movement of mercury to its sources (WHO 1990). Particulate-bound mercury can be converted to insoluble mercury sulfide and precipitated or bioconverted into more volatile or soluble forms that re-enter the atmosphere or are bioaccumulated in aquatic and terrestrial food chains (EPA 1984b). 

Surveillance is a continuous specific observation and measurement relative to control and management (UNESCO, 1978) the primary objective is to trace and observe sources and pathways of specified hazardous substances. If a simple aim of a study is to determine the presence or absence of a specific contaminant in bottom sediment at a given area, then the sediment can be sampled at one or a few sampling stations at fine-grained sediment deposition sites. However, after confirmation of the presence of the contaminant in the sediment, the study may be expanded to determine the extent of sediment contamination by the specific compound or element, with the area, the contaminant s sources, history of the loading of the contaminant, its transport, bioaccumulation, etc. (Mudroch and Azcue, 1995). 

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