Cadmium in water

In addition to systems of the above type, i.e. involving adduct formation, various other types of synergistic extraction systems are recognised and have been reviewed.4 An example is the synergistic influence of zinc in the extraction and A AS determination of trace cadmium in water.5... 

American Society for Testing Materials ASTM Method D3557-95 Cadmium in water... 

The first prototype of a technologically improved IWAO was developed and tested with a membrane based on a new H+-selective ketocyanine dye and a commercial cadmium ionophore [39]. Its incorporation in an IWAO allows a highly sensitive and portable optical system to be obtained for an situ chemical analysis as well. The authors propose a flow injection analysis (FIA) system for the determination of cadmium in water samples using a cadmium-selective IWAO, as an alternative method to the ones generally used in analytical control laboratories. It permits enhanced sensitive signals in short response times by taking advantage of the very thin membranes deposited over the circuit. 

Gunnlaugsson T, Leeb TC, Parkesh R. Highly selective fluorescent chemosensors for cadmium in water. Tetrahedron 2004 60 11239 19. 

The APDC—MIBK extraction system is widely used to determine a variety of metals in water. In both the U.K. [6, 7] and the U.S.A. [8] it is the standard method for the determination of lead and cadmium in water. It is also used as a standard method [8] in the determination of hexavalent chromium. In order to determine total chromium, trivalent chromium is oxidised to hexavalent chromium by bringing the sample to the boil and adding sufficient potassium permanganate solution (0.1 N) dropwise to give a persistent pink colour while the solution is boiled for 10 min. 

Concentrations of cadmium in water are only likely to be of health concern in environments where pH is less than 4.5. 

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 in waters occurs together with zinc, but at much lower concentrations. The background in natural waters ranges from units to tens of pg 1. The artificial sources of cadmiun are wastewaters from the surface finishing of metals, photographic and printing industries. It can be leached from plastic piping as it is a component of their stabilizers. 

Proposed limits for cadmium in water, diet, tissues, air, soils, and sewage sludge for the protection of human health, plants, and animals are shown in Table 5.2. It is noteworthy that the current upper limit of 10.0 xg Cd/L in drinking water for human health protection is not sufficient to protect many species of freshwater biota against the biocidal properties of cadmium or against sublethal effects, such as reduced growth and inhibited reproduction. Ambient water quality criteria formulated for... 

In view of the high toxicity of cadmium it is necessary to be able to determine very small concentrations in water. AAS techniques (Sections 3.4.7.1 and 3.4.7.2) are particularly suitable for determining cadmium in water. Where no AAS facilities are available, it is still possible to use the classical spectrophotometric technique (Section 3.4.7.3) with dithizone and extraction in chloroform. 

Pollutant cadmium in water may arise from mining wastes and industrial discharges, especially from metal plating. Chemically, cadmium is very similar to zinc, and these two metals frequently undergo geochemical processes together. Both metals are found in water in the +2 oxidation state. Cadmium and zinc are common water and sediment pollutants in harbors surrounded by industrial installations. Concentrations of more than 100 ppm dry mass of sediment have been found in harbor sediments. 

Reference Dose and Recommendations about Cadmium in Water, SoU, and Food... 

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