Cadmium release

For the specification of the measurand we need a statement of what we want to measure and at the same time a formula for the result which contains all relevant uncertainty sources. The example in the shde describes the calculation of the result of a determination of the amount of cadmium released from ceramic ware under certain conditions. The result depends on the content of Cd in the extraction solution Co, the volume of the leachate Vl, the surface area ay that is extracted and possibly a dilution factor. These parameters are used to calculate the result. But we also have to consider that the acid concentration, the extraction time and the temperature are influencing the result. Since they are not directly involved in the calculation of the result, we add factors with the value 1. But we assume that this value 1 will have an uncertainty as well. 

Checking a method for ruggedness will highlight the main parameters that need to be carefully controlled. For example, in the determination of cadmium release from ceramic ware, acid is added to the item of ceramic ware and left for 24 hours. During this period, the time, temperature and acid concentration will determine the amount of metal leached. Experiments show that temperature is a key parameter (results change by ca. 5% per °C) and it needs to be strictly controlled, e.g. to within +1 °C. Time is far less critical (result changes by ca. 0.3% per hour) and therefore needs to be less strictly controlled, e.g. 0.5 hour. 

Krishnamurti, G. S. R.. Ciesliiiski. G., Huang, P. M., and Van Rees, K. C. J. (1997). Kinetics of cadmium release from soils as influenced by organic acids implication in cadmium availability. J. Environ. Qual. 26, 271-277. 

Onyatta, J. O., and Huang, P. M. (2003). Kinetics of cadmium release from selected tropical soils from Kenya by low-molecular-weight organic acids. Soil Sci. 168, 234-252. 

Cadmium releases from landfills have been evaluated by the Draft Risk Assessment Report on Cadmium (DRAR 2000). They can be evaluated at less than 0.3 tonnes/y, this representing less than 0.8% of total emissions of cadmium in water in the EU countries. The major contributors to total cadmium emissions into surface waters are zinc and lead producers, fuel combustion for electricity generation, fuel combustion for road transportation, phosphate industries and non-ferrous metallurgy (DRAR 2000). 

Cadmium is widely distributed in the earth s crust at an average concentration of about 0.1-0.2 mg/kg and is commonly found in association with zinc. Volcanic activity is major natural source of cadmium release to the atmosphere. The annual global flux from this source has been estimated to be 820 tons. Deep sea volcanism is also a source of environmental cadmium release, but the role of this process in the global cadmium cycle remains to be quantified (OECD, 1994). About 10-15% of total airborne cadmium emissions arise from natural processes (WHO, 1992a). 

Much work has been done to determine levels of extractable cadmium leached from colored articles. This has been done to determine how much cadmium is likely to be released in food contact applications, and to predict cadmium release from waste products in landfill sites. It has been shown that in all but a few polymers insignificant levels of cadmium are leached out. 

Figure 5 shows the elemental fission product density histories at the exit of the circuit into the containment predicted by VICTORIA. Silver, indium, and cadmium releases have several peaks, which correspond to bursts of control rod segments predicted by CORSOR. Most of the fission product densities tail off at about 7000 s, which corresponds to shutdown of the reactor. However, cesium and iodine densities remain relatively high due to revaporization within the circuit. 

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