Cadmium indicator organisms

Cyanuric Acid. Organic cyanurates and isocyanurates have been prepared as pure materials and their use as metal precipitants has been reported in the literature (25-25). Diallylisocyanurate salts of cadmium, copper, and lead have been described and polyisocyanurates have been cited as precipitants for monovalent and divalent metal ions — including Cd, Hg and Pb —from waste streams (26). Initial tests with 10-34-0 (pH 6.8) indicated that ammonium cyanurate was soluble in the media however, no measurement of the solubility was made and no precipitate was observed. Addition of ammonium cyanurate to a 10-30-0 (pH 6.0) grade phosphate fluid fertilizer containing 40 ppm cadmium indicated low solubility of the reactant in the media and resulted in no cadmium removal at stoichiometries ranging from 25 to 480%. Confirmatory tests... 

The level of 400-500 ug of cadmium indicated as the provisional tolerable weekly intake is based on calculations involving normal and critical values of cadmium in the renal cortex and on what is known of the rate of accxamulation of cadmium in that organ. However, the uncertainties involved are many and varied. For example, the cadmium intake of many populations is presently unknown only scanty data are available on the absorption and excretion of cadmium in various nutritional and metabolic states and it is not very well established that populations with excessive cadmium loads from the diet inevitably develop proteinuria. 

Other studies use soil or sediment samples for a more accurate indication of microbial activity in natural environments. In these samples, organic matter and clay particles play a role in metal toxicity.76112113 Both organic material and clay particles in soil can bind metals and reduce their bioavailability. For example, Pardue et al.87 demonstrated that much less solution-phase cadmium was required to inhibit trichloroaniline (TCA) dechlorination in a mineral-based soil than in a soil containing a higher concentration of organic matter. Other studies have shown that adding clay minerals to a medium mitigates toxicity. Clay minerals, such as kaolinite, montmorillonite, bentonite, and vermiculite, can bind to metals to decrease the amount that is bioavailable.112 115... 

Similar to plants, animals can also be used as bio-indicators. Thus, the analyses of aquatic organisms have been increasingly used to obtain direct measures of abundance and availability of metals in the environment. Mussels can accumulate metals and thus be used to estimate pollutant levels in the environment. Cadmium and lead have been leached from mussels by using dilute nitric acid under US assistance [86]. Leaching was carried out in autosampler cups in order to minimize sample manipulation. 

Metabolomics has made remarkable inroads into the environmental research community. Here, a major emphasis is to understand the impact that environmental stress, such as pollution and climate change, has on wildlife. Indeed, many government organizations monitor the prevalence of pollutants in certain species of wildlife as indicators of the exposure risk within the environment. Studies of Japanese medaka have been conducted to investigate the effects of trichloroethylene, a common environmental pollutant, and the pesticide dinoseb, on the development of fish embryos (44, 45). Similarly, cadmium toxicity has been examined in the bank vole and rat and has revealed changes in lipid metabolism that preceded classical nephrotoxicity (46, 47). Another study investigated the effects of environmental toxins on earthworms (48). In particular, the analysis of earthworm tissue extracts by NMR spectroscopy identified maltose as a potential biomarker for ecotoxicity within a metal-contaminated site. 

A study of iron, cadmium and lead mobility in remote mountain streams of California by Erel et al. (1990) showed that the excess of atmospheric pollution-derived lead and cadmium is rapidly removed downstream. The comparison of truly dissolved, colloidal, and surface particle concentrations measured in the stream with the results of a model of equilibrium adsorption indicates that the mechanism of removal in this organic-poor environment is essentially by uptake onto hydrous iron oxides. The experimentally determined partition coefficients (Dzomback and Morel, 1990) explain the behavior of lead however, they fail to explain the cadmium removal. It is proposed by the authors that cadmium is taken up by surfaces other than hydrous iron oxides. 

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