Synthetic seawater

EPA Environmental Protection Agency SIGMA Sigma Chemicals, Plant Culture Cell , Seawater synthetic basal salt mixture ASTM American Society for Testing and Materials Apha American Public Health Association. 

Fig. 6.1 Determination of iodide via its ion pairing and subsequent extraction/re-extraction at the tricresyl-phosphate-based carbon paste electrode (TCP-CPE). (a) Electrode oxidation of the ion pair formed between the protonated TCP and iodide (b) extraction of the released iodine into the carbon paste bulk, a scheme (c) determination of iodide in seawater (synthetic and spiked sample) by stripping potentiometry, dotted line baseline (blank),/m// lines 1) sample-1-0.1 M HNO3 (pH 1) (2, 3) two standard additions as two aliquots, c(I ) = 50 pg Mode constant current...

Acrylonitrile fibers treated with hydroxides have been reported to be useful for adsorption of uranium from seawater (105). Tubular fibers for reverse osmosis gas separations, ion exchange, ultrafiltration, and dialysis are a significant new appHcation of acryUc fibers and other synthetics. Commercial acryUc fibers have already been developed by Nippon Zeon, Asahi, and Rhc ne-Poulenc. 

Although numerous mud additives aid in obtaining the desired drilling fluid properties, water-based muds have three basic components water, reactive soHds, and inert soHds. The water forming the continuous phase may be fresh water, seawater, or salt water. The reactive soHds are composed of commercial clays, incorporated hydratable clays and shales from drilled formations, and polymeric materials, which may be suspended or dissolved in the water phase. SoHds, such as barite and hematite, are chemically inactive in most mud systems. Oil and synthetic muds contain, in addition, an organic Hquid as the continuous phase plus water as the discontinuous phase. 

Synthetic magnesia is most often produced from seawater, known as seawater magnesia. Seawater contains approximately 1294 ppm Mg. Synthetic magnesia can also be produced from brine wells or lakes which have much higher concentrations of magnesium. Regardless of the source of magnesium, the sea or brine water is treated with hydrated lime, Ca(OH)2, that precipitates Mg(OH)2 ... 

Pipes, valves, fittings, and almost all other components of small equipment are now available in plastic or ceramics, which do not corrode in salt water and are less expensive than the metals now used. Synthetic detergents are now available for use with seawater, although a final rinse with freshwater may be desired. Saltwater sewage can be treated successfully. Dual water systems using freshwater and seawater are already in use on ships and in many island resort hotels. Many of these also have seawater systems for fire fighting. This trend will grow. 

The solubility of carbon dioxide in water is given in Figure 1 (11). Over the temperature range 273—393 K, the solubiUties at pressures below 20 MPa (200 atm) decrease with increasing temperature. From 30 to 70 MPa (300—700 atm) a solubiUty minimum is observed between 343 and 353 K, with solubihties increasing as temperature increases to 393 K. Information on the solubiUty of carbon dioxide in pure water and synthetic seawater over the range 268 to 298 K and 101—4,500 kPa pressure (1—44 atm) is available (12,13). 

Pitting corrosion always remains a worthy subject for study, particularly with reference to mechanism, and the problem conveniently divides into aspects of initiation and growth. For 6061 alloy in synthetic seawater, given sufficient time, pit initiation and growth will occur at potentials at or slightly above the repassivition potential . In an electrochemical study, it was found that chloride ions attack the passive layer as a chemical reaction partner so that the initiation process becomes one of cooperative chemical and electrochemical effects . 

TABLE 9 Synthetic Seawater Composition8 (Ionic Strength 0.629 mol/L)... 

Pigna M, Colombo C, Violante A (2003) Competitive sorption of arsenate and phosphate on synthetic hematites (in Italian). Proceedings XXI Congress of Societa Italiana Chimica Agraria SICA (Ancona), pp 70-76 Quirk JP (1955) Significance of surface area calculated from water vapour sorption isotherms by use of the B. E. T. equation. Soil Sci 80 423-430 Rancourt DG, Fortin D, Pichler T, Lamarche G (2001) Mineralogical characterization of a natural As-rich hydrous ferric oxide coprecipitate formed by mining hydrothermal fluids and seawater. Am Mineral 86 834-851 Raven K, Jain A, Loeppert, RH (1998) Arsenite and arsenate adsorption on ferrihydrite kinetics, equilibrium, and adsorption envelopes. Environ Sci Technol 32 344-349... 

Calculated via addition of TISAB and calibration versus synthetic seawater. 

Spencer and Brewer [144] have reviewed methods for the determination of nitrite in seawater. Workers at WRc, UK [ 145] have described an automated procedure for the determination of oxidised nitrogen and nitrite in estuarine waters. The procedure determines nitrite by reaction with N-1 naphthyl-ethylene diamine hydrochloride under acidic conditions to form an azo dye which is measured spectrophotometrically. The reliability and precision of the procedure were tested and found to be satisfactory for routine analyses, provided that standards are prepared using water of an appropriate salinity. Samples taken at the mouth of an estuary require standards prepared in synthetic seawater, while samples taken at the tidal limit of the estuary require standards prepared using deionised water. At sampling points between these two extremes there will be an error of up to 10% unless the salinity of the standards is adjusted accordingly. In a modification of the method, nitrate is reduced to nitrite in a micro cadmium/copper reduction column and total nitrite estimated. The nitrate content is then obtained by difference. 

These workers conclude that the selective volatilisation technique is highly suitable for the determination of traces of molybdenum in synthetic (and most probably real) seawater samples. It has the advantages of freedom from contamination and loss during sample preparation and is faster, and cheaper, than procedures using separations. 

Elderfield and Greaves [629] have described a method for the mass spectromet-ric isotope dilution analysis of rare earth elements in seawater. In this method, the rare earth elements are concentrated from seawater by coprecipitation with ferric hydroxide and separated from other elements and into groups for analysis by anion exchange [630-635] using mixed solvents. Results for synthetic mixtures and standards show that the method is accurate and precise to 1% and blanks are low (e.g., 1() 12 moles La and 10 14 moles Eu). The method has been applied to the determination of nine rare earth elements in a variety of oceanographic samples. Results for North Atlantic Ocean water below the mixed layer are (in 10 12 mol/kg) 13.0 La, 16.8 Ce, 12.8 Nd, 2.67 Sm, 0.644 Eu, 3.41 Gd, 4.78 Dy, 407 Er, and 3.55 Yb, with enrichment of rare earth elements in deep ocean water by a factor of 2 for the light rare earth elements, and a factor of 1.3 for the heavy rare earth elements. 

Hirose and Sugimura [89] investigated the speciation of plutonium in seawater using adsorption of plutonium (IV)-xylenol orange and plutonium-arsenazo (III) complexes on the macroreticular synthetic resin XAD-2. Xylenol orange was selective for plutonium (IV) and arsenazo (III) for total plutonium. Plutonium levels were determined by a-ray spectrometry. 

Favretto and co-workers [198,206-208] have described direct spectrophoto-metric methods for non-ionic surfactants based on the formation of a sodium picrate surfactant adduct. This method has been applied to seawater. A mean value of 93 1% was obtained in recovery experiments on C12E9 (at an aqueous concentration of 0.10 mg/1) extracted from synthetic sea water by means of this... 

In seawater, the major chemical species of copper are Cu(OH)Cl and Cu(OH)2 and these account for about 65% of the total copper in seawater (Boyle 1979). The levels of copper hydroxide (Cu(OH)2) increase from about 18% of the total copper at pH 7.0 to 90% at pH 8.6 copper carbonate (CuC03) dropped from 30% at pH 7.0 to less than 0.1% at pH 8.6 (USEPA 1980). The dominant copper species in seawater over the entire ambient pH range are copper hydroxide, copper carbonate, and cupric ion (USEPA 1980). Bioavailability and toxicity of copper in marine ecosystems is promoted by oxine and other lipid soluble synthetic organic chelators (Bryan and Langston 1992). 

Mussel, Mytilus galloprovincialis soft parts purged for 48 h in aerated synthetic seawater vs. not purged 6.9 DW vs. 13.1 DW 118... 

Synthetic pyrethroids now account for at least 30% of the world insecticide market and are rapidly replacing other agricultural chemicals for control of insect pests. Fenvalerate is one of the more widely used synthetic pyrethroid insecticides. It is derived from a combination of a-cyano-3-phenoxybenzyl alcohol and a-isopropyl phenylacetate ester. Technical fenvalerate is a mixture of four optical isomers, each occurring in equal amounts but with different efficacies against insect pests. Fenvalerate does not usually persist in the environment for >10 weeks, and it does not accumulate readily in the biosphere. Time for 50% loss (Tb 1/2) in fenvalerate-exposed amphibians, birds, and mammals was 6 to 14 h for reptiles, terrestrial insects, aquatic snails, and fish it was >14 h to <2 days and for various species of crop plants, it was 2 to 28 days. Fenvalerate degradation in water is due primarily to photoactivity, and in soils to microbial activity. Half-time persistence in nonbiological materials is variable, but may range up to 6 days in freshwater, 34 days in seawater, 6 weeks in estuarine sediments, and 9 weeks in soils. 

The use of synthetic media is preferable to natural filtered and/or sterilised media, as trace substances are expensive to remove from natural waters. In addition to this, the reproducibility of assays is improved if synthetic media are used. Different artificial seawater compositions have been used in toxicity testing. From the media investigated by our group, (see Table 7.1.2) the ASTM substitute ocean water [66] gave the best results for growing microalgae. 

Manceau A, Schlegel ML, Musso M, Sole VA, Gauthier C, Petit PE, Trolard F (2000) Crystal chemistry of trace elements in natural and synthetic goethite. Geochim Cosmochim Acta 64 3643-3661 Marchitto Jr. TM, Curry WB, Oppo DW (2000) Zinc concentrations in benthic foraminifera reflect seawater chemistry. Paleoceanogr 15 299-306. 

The trimesoyl chloride could be mixed with isophthaloyl chloride to produce copolyamide barrier layers. Salt rejections toward synthetic seawater improved as the isophthalamide content of the barrier layer Increased. Surprisingly, membrane flux passed through a peak rather than simply declining as a function... 

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