Trace metals toxicity

Ion exchange as well as lime treatment is another method that can be applied in this process to reduce some of the toxic trace metals in the wastewater from the plant. 

Jenkins, D.W. 1980. Biological monitoring of toxic trace metals. Volume 2. Toxic trace metals in plants and animals of the world. Part 1. 11.S. Environ. Protection Agen. Rep. 600/3-80-090. 503 pp. 

Falchuk, K. 1988. Zinc deficiency and the E. gracilis chromatin. Pages 75-91 in A.S. Prasad (ed.). Essential and Toxic Trace Metals in Human Health and Disease. Alan R. Liss, NY. 

No carrier is completely specific for a given trace metal metals of similar ionic radii and coordination geometry are also susceptible to being adsorbed at the same site. The binding of a competing metal to an uptake site will inhibit adsorption as a function of the respective concentrations and equilibrium constants (or kinetic rate constants, see below) of the metals. Indeed, this is one of the possible mechanisms by which toxic trace metals may enter cells using transport systems meant for nutrient metals. The reduced flux of a nutrient metal or the displacement of a nutrient metal from a metabolic site can often explain biological effects [92]. 

A number of potentially toxic trace metal and organic species are highly enriched at the surfaces of many types of environmental particles (11-14). 

Increased concentration of toxic trace metals in the oceans, liberated by hydrothermal fluids from oceanic plateau lava piles, may well have been a contributory factor to the demise of some marine organisms around the CTB (Wilde et al., 1990). The upwelling of deep ocean trace metals and... 

Although mercury has been used in spring tonics, as a cure for syphilis, and a panacea for other afflictions, it is now recognized as a highly toxic trace metal that concentrates in aquatic food webs. According to Clarkson (1997), the principal human exposure to inorganic mercury species is from elemental mercury vapor, which is derived principally from industries such as gold and silver... 

These results suggest that evaporative playa lake sediments and dusts generated from dry lake beds can be potentially significant sources of reactive, alkaline material with high levels of soluble, potentially toxic trace metals and metalloids. Further studies are needed to determine whether such dusts pose a substantial health hazard to those exposed to them on a regular basis. 

Prakash (1971) reviewed the potential importance of riverine humic materials in stimulation of coastal phytoplankton productivity, which he ascribed to complexation of toxic trace metals. However, the actual responsibility of the riverine material for such complexation has yet to be demonstrated. 

Musani, Lj., Valenta, P., Nurnberg, H. W., Konrad, Z., and Branica, M. (1980). On the chelation of toxic trace metals by humic acid of marine origin. Estuarine Coastal Mar. Sci. 11, 639-649. 

The adsorption-isotherm and ion-exchange models are of limited applicability when modeling complex and variable natural systems, particularly when the sorbates of interest are minor or trace ionic species (<10 " to 10" mol/kg), and the sorbents exhibit pH-dependent surface charge. For such conditions, the adsorption of trace ionic species often takes place against the net surface charge of the sorbent. This is the behavior of most toxic trace metal cations, including those of the heavy metals and radionuclides when adsorbed by positively charged metal oxyhydroxides, for example. 

ROS may also affect microorganisms through the production of toxic trace metal species. For example, the photolysis of organic Cu-complexes and interactions with 02 may increase the Cu bioavailability and hence Cu toxicity to phytoplankton. This interaction with transition metals is likely to be one of the main processes through which photochemically produced 02 , or other charged ROS, can have an adverse affect on aquatic biota but further studies are needed to ascertain the ecological impact of these types of reactions in natural waters. 

Bioavailability" is a quantitative measure of the utilization of an element under specific conditions, and includes mechanisms such as absorption, transport to a site of metabolic/toxic activity, biotransformation to a metabolically active/toxic form, retention/accumulation, and excretion (McKenzie in Nriagu, 1984). Bioavailable species of a pollutants can be increased by small particle size or volatility, aque-ous/lipid solubility, complexation, and - for metals - by elements or complexes which mimic essential nutrients and thus are handled by specific active transport processes. Assessment of pollutant bioavailability in sediments is difficult due the compexicity of the system, and the following questions have been raised with respect to toxic trace metals (Luoma, 1983 Salomons Forstner, 1984 Campbell et al., 1988) ... 

Because as noted in the Harvard project "most of the toxic trace metals, organics, or acidic materials emitted from automobiles or fossil fuel combustion are highly concentrated in the fine particle fraction" and since diesel engine penetration in Europe is much greater than in the United States, the potential cancer risk is also substantially greater. 

Golimowski, J., Valenta, P., Stoeppler, M. and Nurnberg, H.W. (1979). A rapid high-performance analytical procedure with simultaneously voltammetric determiation of toxic trace metals in urine. Talanta, 26.649. 

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