Cadmium sediment

Provide an SOP for the determination of cadmium in lake sediments by atomic absorption spectrophotometry using a normal calibration curve. 

The isolation of zinc, over 90% of which is from sulfide ores, depends on conventional physical concentration of the ore by sedimentation or flotation techniques. This is followed by roasting to produce the oxides the SO2 which is generated is used to produce sulfuric acid. The ZnO is then either treated electrolytically or smelted with coke. In the former case the zinc is leached from the crude ZnO with dil H2SO4, at which point cadmium is precipitated by the addition of zinc dust. The ZnS04 solution is then electrolysed and the metal deposited — in a state of 99.95% purity — on to aluminium cathodes. 

In the profiles of the core from the industrial area, mercury displays the highest accumulation. Mercury in this area, close to the industrial district, has probably derived from a large chloralkali plant which has employed mercury cathodes since the fifties. Whereas, at present, very severe measures are taken to prevent mercury spills into the Lagoon, in the past, polluted waters and solid materials were discharged almost untreated. In the most superficial strata a marked decrease in the accumulations is, in fact, recorded. Lead and Cd accumulations are lower here by a factor of 5-10. The presence of cadmium in the sediments of the Lagoon has been referred to sphalerite (ZnS) processing on the basis of a strict concomitant... 

The widespread use of many metals such as silver, cadmium, copper, mercury, nickel, lead, and zinc has resulted in their accumulation in the environment. Sediments are often the repositories of toxic metals (e.g.. Table 15-2). For example, copper is used as an anti-biofouling agent in marine paints and many harbor sediments contain markedly elevated levels of copper. 

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. 

Swartz, R. C. Ditzworth, G. R., Schultz, D. W. and Lamberson, J. O. (1985). Sediment toxicity to a marine infaunal amphipod cadmium and its interaction with sewage sludge. Mar. Environ. Res. 18, 133-153. 

The pollutants of concern are the same as in wet basic oxygen furnaces, but the concentration of metals (primarily lead and zinc, but also arsenic, cadmium, copper, chromium, and selenium) in wastewater is higher because of the higher percentage of scrap charged. Wastewater treatment operations are similar to those for the wet basic oxygen furnaces, including sedimentation in clarifiers or thickeners and recycle of the water.14... 

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... 

Bloom NS, Crecelius EA, 1987. Distribution of silver, mercury, lead, copper, and cadmium in Central Puget Sound sediments. Marine Chemistry 21 377-390. 

Hickey M.G., Kittrick J.A. Chemical partitioning of cadmium, copper, nickel, and zinc in soils and sediments containing high levels of heavy metals. J Environ Qual 1984 13 372-376. 

Khalid R.A., Gambrell, R.P., Patrick, W.H.Jr., Chemical availability of cadmium in Mississippi River sediment. J Environ Qual 1981 10 523-528. 

Mahan K.I., Foderaro T.A., Garza T.L., Martinez R.M., Maroney G.A., Trivisonne M.R., Willging E.M. Microwave digestion techniques in the sequential extraction of cadmium, iron, chromium, manganese, lead and zinc in sediments. Anal Chem 1987 59 938-945. 

Andres, S., F. Ribeyre, and A. Boudou. 1998. Effects of temperature and exposure duration on transfer of cadmium between naturally contaminated sediments and burrowing mayfly nymphs (Hexagenia rigida). Arch. Environ. Contam. Toxicol. 35 295-301. 

Bryan, G.W. and L.G. Hummerstone. 1973. Adaptation of the polychaete Nereis diversicolor to estuarine sediments containing high concentrations of zinc and cadmium. Jour. Mar. Biol. Assoc. UK. 53 839-857. 

Schlekat, C.E., A.W. Decho, and G.T. Chandler. 1998. Sorption of cadmium to bacterial extracellular polymeric sediment coatings under estuarine conditions. Environ. Toxicol. Chem. 17 1867-1874. 

Douben, P.E.T. and J.H. Koeman. 1989. Effect of sediment on cadmium and lead in the stone loach (Noema-cheilus barbatulus L.). Aquat. Toxicol. 15 253-268. 

Beauvais, S.L., J.G. Wiener, and G.J. Atchison. 1995. Cadmium and mercury in sediment and burrowing mayfly nymphs (Hexagenia) in the upper Mississippi River, USA. Arch. Environ. Contam. Toxicol. 28 178-183. 

Martin, D.B. and W.A. Hartman. 1984. Arsenic, cadmium, lead, mercury, and selenium in sediments of riverine and pothole wetlands of the north central United States. Jour. Assoc. Off. Anal. Chem. 67 1141-1146. 

Ward, T.J., R.L. Correll, and R.B. Anderson. 1986. Distribution of cadmium, lead and zinc amongst the marine sediments, sea grasses and fauna, and the selection of sentinel accumulators, near a lead smelter in South Australia. Austral. Jour. Mar. Freshwater Res. 37 567-585. 

Chemical analysis of the Meza River and its tributaries revealed significant heavy metal pollution of the upper Meza River sediments with lead, zinc, and some molybdenum, cadmium and arsenic enrichments. The trend of Cd and As is similar to trend of Pb and Zn, which is in agreement with the fact that Cd and As are associated with Pb and Zn in ore minerals (Strucl, 1984 Fux Gosar, 2007). In the lower Meza valley, these heavy metal concentrations decreased somewhat. 

---