Cadmium/calcium ratio

The cadmium/calcium ratio is a proxy for the nutrient (phosphate) content of sea water that reflects abyssal circulation patterns. Carbon isotope ratios also reflect deep-ocean circulation and the strength of organic matter fluxes to the seafloor. 

Figure 5. Cadmium over calcium ratio in DH vs. the same ratio in the solution. The slope (D) is about 1.5 10. Residence time 1200 (circles) to 3600 s.

Figure 7. Cadmium over calcium ratio in HH versus the same ratio in the solution for various phosphate concentrations.

In contrast to the ionic complexes of sodium, potassium, calcium, magnesium, barium, and cadmium, the ease with which transition metal complexes are formed (high constant of complex formation) can partly be attributed to the suitably sized atomic radii of the corresponding metals. Incorporated into the space provided by the comparatively rigid phthalocyanine ring, these metals fit best. An unfavorable volume ratio between the space within the phthalocyanine ring and the inserted metal, as is the case with the manganese complex, results in a low complex stability. 

Cadmium. Cadmium appears to be compatible or very mildly incompatible, similar to zinc. Almost nothing is known about which minerals it prefers. From a crystal-chemical view, cadmium has similar ionic radius and charge to calcium, but a tendency to prefer lower coordination due to its more covalent bonding with oxygen (similar to zinc and indium). Cadmium in spinel Uierzolites varies from 30 ppb to 60 ppb (BVSP) and varies in basalts from about 90 ppb to 150 ppb (Hertogen et al., 1980 Yi et al., 2000). Cd/Zn is —10 in peridotites (BVSP) and the continental cmst (Gao etal., 1998), and —1.5 X 10 in basalts (Yi etai, 2000). We adopt the mean of these ratios (1.2 X 10" ). 

In order to estimate paleoceanographic nutrient levels, and thereby explore links between nutrient variability, atmospheric CO2 and climate change, a range of nutrient proxies have been developed. The ratio of cadmium (Cd) to calcium (Ca) in benthic foraminifera has been used as a proxy for dissolved phosphate, based on the observation that dissolved cadmium and phosphate concentrations are linearly correlated in modern oceanic waters (Boyle, 1988). While the basis of the Cd PO4 relationship is not understood, from either a biochemical or geochemical standpoint (e.g., Cullen et al., 2003),... 

Data concerning the toxicity of the four discussed toxic minerals are presented in Tables 4.5 and 4.6. The uptake of elements is not entirely independent of one another. Elements of similar chemical properties tend to be taken up together. Sometimes one element has an inhibiting effect on another, or there can be a synergistic effect, e.g., enhancement of absorption of calcium in the presence of adequate amounts of phosphorus, or cadmium and lead hindering calcium and iron absorption, or zinc and copper antagonism and their influence on the ratio of Zn/Cu on copper deficiency. 

The traditional stabilizer for hard PVC, harking back to the beginnings of PVC processing, is the cadmium-based stabilizer that was subsequently replaced by lead-based stabilizers for the most part in the 1980s. The demand for PVC formulae free of heavy metals has today led to an increasing use of calcium-zinc stabilizers free of heavy metals [23]. The many different demands made on modem PVC mixtures can hardly be met by one stabilizer alone, so that current practice frequently combined different stabilizer systems. Stabilizers are added to mixtures at ratios of around 14% by mass. 

While severe cadmium toxicity like that which occurred near Toyama has not been found elsewhere, it is suspected that mild to moderate types of chronic cadmium toxicity may cause disorders of the kidneys leading to high blood pressure. However, the milder forms of cadmium poisoning may be counteracted by such essential minerals as calcium, copper, iron, manganese, selenium, and zinc. Therefore, a few scientists believe that high ratios of cadmium to zinc in the diet and in the various tissues of the body are better indicators of potential cadmium toxicities than the dietary and tissue levels of this toxicant alone. 

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