Sedimentation selenium

The most recent comprehensive assessment of the quality of rivers in the USA is that of Smith et al. 12), This followed an earlier assessment by Wolman et al. in 1971 (iS). The former 1987 assessment was based on 24 water quality measures from 161-383 stations around the country covering the period 1974-1981. Trends observed included major increases in nitrate, phosphorous, sodium, suspended sediment, fecal bacteria, dissolved oxygen deficit, arsenic and selenium. Major decreases were observed with nitrate, suspended sediment, fecal bacteria, dissolved oxygen deficit and lead. 

Selenium was discovered in 1817 by J. J. Berzelius (1779-1848) and J. G. Gahn (1745-1818) in the sediment taken from the lead chamber of a sulfuric acid plant in Gripsholm, Sweden. Its name was derived from the Greek word aekr]vr] (selene), for moon, because of its chemical similarity to tellurium-earth. 

The selenium species that are drawing most attention are Se(IV) and Se(VI) in water and sediments, and the biomethylated products (dimethylselenide and dimethyldi-selenide) that are spread into the environment (Camara et al. 1995). Se-species in food (including Se-cysteine and other species in yeast) are in the limelight (Crews 1998) because of their beneficial effect on human health and their increasing use as nutraceuticals. 

Camara C, Cobo MA, Palacios R, Munoz R, and Donard OFX (1995) Selenium speciation analyses in water and sediment matrices. In Quevauviller Ph, Maier EA and Griepink B, eds. Quality assurance for environmental analysis, pp 237-262. Elsevier, Amsterdam. 

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... 

Tokunaga T., Brown G.E. Jr., Pickering I.J., Sutton S.R., Bajt S. Selenium transport between ponded waters and sediments. Environ Sci Technol 1997 31 1419-1425. 

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. 

Speyer, M.R. 1980. Mercury and selenium concentrations in fish, sediments, and water of two northwestern Quebec lakes. Bull. Environ. Contam. Toxicol. 24 427-432. 

In coastal environment, detrital and authigenic Fe and Mn oxides, which accumulate in oxic surface sediments, play a pivotal role in determining the geochemical behaviour of arsenic (Mucci et al., 2000) and selenium (Belzile et al., 2000). Arsenic and selenium differ in their affinities for metal oxide surfaces. Although both adsorb onto iron oxides, arsenate (As(V)) adsorbs more strongly than arsenite (As(lll)), and selenite (Se(IV)) adsorbs more strongly than selenate (Se(VI)) (Belzile et al., 2000). 

Belzile, N., et al. 2000. Early diagenetic behavior of selenium in freshwater sediments. Applied Geochemistry, 15, 1439-1454. 

Takayanagi, K. Belzile, N. 1988. Profiles of dissolved and acid-leachable selenium in a sediment core from the Lower St. Lawrence Estuary. Marine Chemistry, 24, 307-314. 

The bioavailability of selenium to a benthic deposit-feeding bivalve, Macoma balthica from particulate and dissolved phases was determined from AE data. The selenium concentration in the animals collected from San Francisco Bay was very close to that predicted by a model based on the laboratory AE studies of radiolabelled selenium from both particulate and solute sources. Uptake was found to be largely derived from particulate material [93]. The selenium occurs as selenite in the dissolved phase, and is taken up linearly with concentration. However, the particle-associated selenium as organoselenium and even elemental selenium is accumulated at much higher levels. The efficiency of uptake from the sediment of particulate radiolabelled selenium was 22%. This contrasts with an absorption efficiency of ca. 86% of organoselenium when this was fed as diatoms - the major food source of the clam. The experiments demonstrated the importance of particles in the uptake of pollutants and their transfer through the food web to molluscs, but the mode of assimilation was not discussed. 

EPA Method 7063 Arsenic and selenium in sediment samples and extracts by ASV... 

Spectrofluorimetric methods are applicable to the determination of aliphatic hydrocarbons, and humic and fulvic acids in soil, aliphatic hydrocarbons polyaromatic hydrocarbons, optical whiteners, and selenium in non-saline sediments, aliphatic aromatic and polyaromatic hydrocarbons and humic and fulvic acids in saline sediments. The only application found in luminescence spectroscopy is the determination of polychlorobiphenyl in soil. Generally speaking, concentrations down to the picogram (pg L 1), level can be determined by this technique with recovery efficiencies near f00%. 

This technique has been applied to the determination of arsenic, selenium, organocompounds of arsenic, mercury and tin in soils, carbohydrates, total sulphur, arsenic, antimony, bismuth, selenium and organocompounds of mercury, tin and silicon in non-saline sediments, arsenic, bismuth, selenium or organotin compounds in saline sediments and arsenic and selenium in sludges. 

Cutter [122] used a selective hydride generation procedure as a basis for the differential determination of arsenic and selenium species in sediments. Goulden et al. [123] also discuss the determination of arsenic and selenium in sediments by atomic absorption spectrometry. 

Goulden et al. [123] have described a semi-automated system for the determination of arsenic and selenium by hydride generation-industrively coupled plasma atomic-emission spectrometry. Sediments are brought into a solution by fusion with sodium hydroxide. 

The optimal reaction conditions for the generation of the hydrides can be quite different for the various elements. The type of acid and its concentration in the sample solution often have a marked effect on sensitivity. Additional complications arise because many of the hydrideforming elements exist in two oxidation states which are not equally amenable to borohydride reduction. For example, potassium iodide is often used to pre-reduce AsV and SbV to the 3+ oxidation state for maximum sensitivity, but this can also cause reduction of Se IV to elemental selenium from which no hydride is formed. For this and other reasons Thompson et al. [132] found it necessary to develop a separate procedure for the determination of selenium in soils and sediments although arsenic, antimony and bismuth could be determined simultaneously [133]. A method for simultaneous determination of As III, Sb III and Se IV has been reported in which the problem of reduction of Se IV to Se O by potassium iodide was circumvented by adding the potassium iodide after the addition of sodium borohydride [134], Goulden et al. [123] have reported the simultaneous determination of arsenic, antimony, selenium, tin and bismuth, but it appears that in this case the generation of arsine and stibene occurs from the 5+ oxidation state. 

All four dissolution procedures studied were found to be suitable for arsenic determinations in biological marine samples, but only one (potassium hydroxide fusion) yielded accurate results for antimony in marine sediments and only two (sodium hydroxide fusion or a nitricperchloric-hydrofluoric acid digestion in sealed Teflon vessels) were appropriate for determination of selenium in marine sediments. Thus, the development of a single procedure for the simultaneous determination of arsenic, antimony and selenium (and perhaps other hydride-forming elements) in marine materials by hydride generation inductively coupled plasma atomic emission spectrometry requires careful consideration not only of the oxidation-reduction chemistry of these elements and its influence on the hydride generation process but also of the chemistry of dissolution of these elements. 

Neutron activation analysis has been used to determine selenium in soil [144-148], Nadkarni and Morrison [149] estimated 47 elements in lake sediments and found 0.3-1.01pg selenium per gram using neutron activation analysis. Dong et al. [162] used mixtures of phosphoric acid, nitric acid and hydrogen peroxide in the digestion of soils prior to the determination of selenium. 

Wiersma and Lee [164] determined selenium in lake sediments. The sample is digested with 4 1 concentrated nitric acid 6% perchloric acid and the residue treated with 6M hydrochloric acid then reduced with H PO. The fluorescing agent used was 2,3 diaminonaphthalene. 3 2... 

The atomic absorption spectrophotometric methods discussed in section 12.10.2.2 [122, 124] has been applied to the determination of selenium in sediments. Itoh et al. [165] and Cutter [122] (section 12.10.2.2) have used hydrogen generation-atomic absorption spectrophotometric techniques to determine selenium in non-saline sediments. Cutter [122] was able to distinguish between selenite, selenate, total selenium and organic selenium in sediments. 

The inductively coupled plasma technique [123] discussed in section 12.10.2.3 has been applied to the determination of selenium in non-saline sediments. 

Cheam et al. [128] have developed a Great Lakes reference sediment for selenium. 

Terada et al. [166] determined 0.3-lppm selenium in marine sediments after converting the element to stannic bromide which was distilled off and assayed colorimetrically as piazselenol. 

Siu and Berman [163] determined selenium in marine sediments in amounts down to 0.2pg (or 20ng g 1 of sediment) with a precision of 7%. This method is based on the fact that 1,2 diaminobenzene (o-phenylene diamine) and its derivatives react selectively and quantitatively with selenium IV (average accuracy 94 5%) to form piazselenols that are both volatile and stable. Piazselenols can be determined by electron capture gas chromatography. The sediments were digested as follows. A 0.5g sample was placed in a poly(tetrafluoroethylene) pressure decomposition vessel. A... 

In this method a 0.5 pg portion of sediment was decomposed by acid digestion in a PTFE bomb according to the procedure described by Siu and Berman [163] and diluted to 50mL in 1M hydrochloric acid. Total selenium was determined by using 500pL aliquots delivered into the hydride cell containing 5mL of 0.5M hydrochloric acid. 

Biological action is very important in Se redox transformations. Rates of abiotic selenium redox reactions tend to be slow, and in soils and sediments, Se(VI), Se(IV), Se(0) and organically bormd Se often coexist (Tokrmaga et al. 1991 Zhang and Moore 1996 Zawislanski and McGratii 1998). Bacteria use Se(VI) and Se(IV) as eleclron acceptors (Blum et al. 1998 Dungan and Frankenberger 1998 Oremland et al. 1989), or oxidize elemental Se (Dowdle and Oremland 1998), and it is likely that most of the important redox transformations are microbially mediated. 

Bruchert V, Knoblauch C, Jorgensen BB (2001) Controls on stable sulfur isotope fractionation during bacterial sulfate reduction in Arctic sediments. Geochim Cosmochim Acta 65 763-776 Bryan BA, Shearer G, Skeeters JL, Kohl DH (1983) Variable expression of the nitrogen isotope effect associated with denitrification of nitrate. J Biol Chem 258 8613-8617 Canfield DE (2001) Biogeochemistry of sulfur isotopes. Rev Mineral Geochem 43 607-636 Chau YK, Riley JP (1965) The determination of selenium in sea water, silicates, and marine organisms. Anal Chim Acta 33 36-49... 

Fan TWM, Higashi RM (1998) Biochemical fate of selenium in microphytes natural bioremediation by volatilization and sedimentation in aquatic environments. In Environmental Chemistry of Selenium. Frankenberger Jr. WT, Engberg RA(eds), Marcel Dekker, New York, p 545-564... 

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