Water, cadmium concentration

As is the case with assessments of the toxicity of dissolved trace metals, the development of sediment quality criteria (SQC) must be based on the fraction of sediment-associated metal that is bioavailable. Bulk sediments consist of a variety of phases including sediment solids in the silt and clay size fractions, and sediment pore water. Swartz et al. (1985) demonstrated that the bioavailable fraction of cadmium in sediments is correlated with interstitial water cadmium concentrations. More recent work (e.g., Di Toro et al, 1990 Allen et al., 1993 Hansen et al, 1996 Ankley et ai, 1996, and references therein) has demonstrated that the interstitial water concentrations of a suite of trace metals is regulated by an extractable fraction of iron sulfides. 

Figure 4. Japanese River Water Cadmium Concentration and NiCd Battery Production...

Manganese oxides have been used to remediate contaminated soils as well. Hydrous manganese oxides decreased Cd and Pb in rye grass (Lolium spp.) and tobacco (Nicotiana tabacum L.) from soils with pH 7.4-7.8 (Mench et al., 1994). Cadmium concentrations decreased in water and in 0.1 M Ca(N03)2 and acetic acid extracts of treated soils (Mench et al., 1994). 

Studies of 30 to 60 days duration with three comparatively sensitive species of freshwater fishes demonstrated that concentrations of >1 and <3 pg Cd/L in water of low alkalinity caused reductions in growth, survival, and fecundity of brook trout (Salvelinusfontinalis), the most sensitive species tested (Table 1.3). Under conditions of increasing alkalinity, the maximum allowable cadmium concentration range for brook trout increased to >7 and <12 pg/L a similar case was made for the walleye (Stizostedion vitreum vitreum Table 1.3). 

Two species of freshwater aquatic mosses (Fontinalis dalecarlica, Platyhypnidium riparoides) exposed to concentrations between 0.5 and 6.5 pg Cd/L for 28 days had accumulation factors as high as 137,000 and 158,000, respectively (Gagnon etal. 1998). Accumulations increased with increasing cadmium concentration and decreasing water hardness. Cadmium tended to persist in these mosses. During a depuration period of 28 days following the 28-day exposure, only 37 to 48% of the accumulated cadmium was eliminated (Gagnon et al. 1998). 

Westemhagen, H.V., V. Dethlefsen, and H. Rosenthal. 1980. Correlation between cadmium concentrations in the water and tissue residue levels in dab, Limanda limanda L., and plaice, Pleuronectes platessa L. Jour. Mar. Biol. Assoc. UK. 60 45-58. 

Most fish taken around the UK coast contain little cadmium, with the average being less than 0.2 mg/kg. The results of a routine surveillance exercise are given in Table 7.2.15 The 144 samples analysed were collected between 1995 and 1997. It was found that marine fish had concentrations of less than the LOD of 0.01 mg/kg, while shellfish contained higher concentrations than do most other foods, but, with the exception of lobster, whelks and crabs, shellfish from unpolluted waters rarely have an average cadmium concentration greater than 1 mg/kg. However, the body meat of crabs (brown meat) may often contain higher concentrations. 

Warren, L.A., Tessier, A. and Hare, L. (1998) Modeling cadmium accumulation by benthic invertebrates in situ the relative contributions of sediment and overlying water reservoirs in organism cadmium concentrations, Limnology and Oceanography 43, 1442-1454. 

It should be pointed out that few elements are present in most natural waters at concentrations where flame spectroscopic techniques are directly applicable. Those that are include calcium, magnesium, sodium, potassium, and, in some samples and if conditions are very carefully optimized, manganese, iron, and aluminium. Zinc, and sometimes cadmium, may be determined directly by AFS. Mercury and hydride-forming elements may be determined if cold vapour and hydride generation sample introduction techniques are employed, as discussed in... 

Ultrasonic nebulizers have also been employed in continuous flow systems as interfaces between sample preparation steps in the analytical process and detection by virtue of their suitability for operating in a continuous mode. Thus, preconcentration devices have commonly been coupled to atomic spectrometers in order to increase the sensitivity of some analytical methods. An enhancement factor of 100 (10 due to USNn and 10 due to preconcentration) was obtained in the determination of platinum in water using a column packed with polyurethane foam loaded with thiocyanate to form a platinum-thiocyanate complex [51]. An enhancement factor of 216 (12 with USNn and 18 with preconcentration) was obtained in the determination of low cadmium concentrations in wine by sorption of metallic complexes with pyridylazo reagents on the inner walls of a PTFE knotted reactor [52]. One special example is the sequential determination of As(lll) and As(V) in water by coupling a preconcentration system to an ICP-AES instrument equipped with a USN. For this purpose, two columns packed with two different resins selective for each arsenic species were connected via a 16-port valve in order to concentrate them for their subsequent sequential elution to the spectrometer [53]. 

CO2 and N2. Excess chlorine gas (i.e., chlorine which did not form hypochlorite) converted the cyanide to cyanate, which was subsequently oxidized by hypochlorite. Cadmium was precipitated from the water due to an increase in the solution pH. A platinum-plated niobium screen was the anode and a stainless steel screen was used as the cathode. At an applied potential of 6.0 V, resulting in a current of 6.0 A, the cadmium concentration decreased from 17.4mg/dm to 0.01 mg/dm, while the cyanide concentration declined from 54 mg/dm to zero in 80 min of cell operation. 

The use of Cd/Ca measurements in the tests of benthic foraminifera for deep-water nutrient reconstructions was developed in parallel with the carbon isotope method. Cadmium concentrations in seawater follow a nutrient-like distribution, while calcium concentrations simply reflect variations in salinity. The benthic foraminifera incorporate the cadmium and calcium into their shells in proportion to their presence in seawater, which allows for the reconstruction of deep-water cadmium (and thus macronutrient) distributions. 

However, it is clear from many tracers that there was continued ventilation of deep waters in the North Atlantic as well. Boyle and Keigwin (1982) argued that the fact that reconstructed cadmium concentrations in the deep North Atlantic were still lower than average ocean values suggests that there was not a... 

Due to the wide use of cadmium-based products, cadmium is widely distributed in the environment. The cadmium content in soil and water has been increasing as a result of disposal of cadmium-contaminated waste and the use of cadmium-containing fertilizers (particularly on cereal crops). Commercial sludge, contaminated with cadmium, has been used to fertilize agricultural fields. Cadmium concentrations in urban air are quite low, because of regulation of industrial air emissions. Lead and zinc smelters and waste incineration account for the majority of cadmium present in ambient air. 

The total runoff data have been taken from (Global Data Sets. .., 1988). The value of maximum permissible level of lead concentration in the water is equal to 0.03 mg/L, the value of maximum permissible level of cadmium concentration in the water is equal to 0.005 mg/L (MPLs Act No2932-83, 1986). 

This approach was further modified in order to avoid the need for ion-exchange concentration after the electrolytic process [305]. Two electrolytic cells were placed in the main carrier stream, one for retaining the potential interferents and the other for in-line cadmium concentration. Cadmium was concentrated and eluted solely by modifying the applied potential in the second cell. This innovation was applied to the analysis of river waters using tetraphenylporphine tetrasulfonic acid as the colourforming reagent and 2,2 -bipyridine as a catalyst. With a 29 min concentration time, precise results (r.s.d. = 2.1%) were obtained and the detection limit was 0.45 pg L 1. 

---