Extraction from seawater sediment

Transuranic elements are extracted from seawater by coprecipitation with either ferric hydroxide or calcium/strontium oxalate or are leached from sediments with 8M nitric acid. Radiochemical separations are used to aruilyze PUy... 

The transuranic elements extracted from seawater or sediments are further purified such that ... 

Dow seawater A process for extracting magnesium from seawater. Calcined dolomite (CaO-MgO, dololime), or calcined oyster shell, is added to seawater, precipitating magnesium hydroxide. This is flocculated, sedimented, and filtered off. For use as a refractory it is calcined for the manufacture of magnesium chloride for the manufacture of magnesium metal, it is dissolved in hydrochloric acid. Developed by the Dow Chemical Company and later operated by the Steetly Company in West Hartlepool, UK, and Sardinia. 

Different sampling methods often result in collection of different components of the element or compound of interest. Most seawater samples are collected in bottles, filtered to remove particles and analyzed directly or after preconcentration of minor components. Particulate matter from the water column is collected by filtration or with sediment traps. Sediment samples are collected in cores that recover intact chronological sequences and are commonly subsampled, dried and ground to a powder. Pore waters are extracted from sediments by squeezing or suction, dialysis, and centrifugation. 

Fig. 9.4 Distribution of carbonate species (a and c) and calcium species (b and d) in seawater after Nordstrom et al. 1979 (a and b) and in an anoxic pore water (c and d). The pore water sample was extracted from the core previously shown in Figure 3.1 and was taken from a depth of 14.8 m below the sediment surface. The calculation of species distributions was performed with the program PHREEQC (Parkhurst 1995)...

Bulleid, N.C., 1978. An improved method for the extraction of ATP from marine sediment and seawater. Limnol. Oceanogr., 23 174—178. 

Although iodine in oceans is only 0.8% of the total iodine on the earths crust (Muramatsu and Wedepohl, 1998), it enters the human food chain via three important processes (1) the evaporation of iodine from seawater into the air, its subsequent deposition onto soils and in fresh water, and final incorporation into terrestrial plants and animals (2) a higher incorporation into microorganisms, seaweeds, and fish, which are used as food and nutritional supplements and (3) extraction of iodine from pore water that contains no sediments and higher concentrations of iodine and using it for various purposes, e.g., as an additive to edible salt. 

In addition, the research on sediment phosphorus can supply information about the paleoenvironment. The information about the environment and biogeochemistry of phosphorus extracted from the South Sea shelf slope sediments showed that the supply of terrigenous phosphorus for the sea was steady overall. The change in phosphorus contents in different depths was the result of climate and environmental changes. The vertical distribution of phosphorus had an opposite trend to calcium carbonate and Cd in sediment. The ebb and flow between CO2 and in seawater calculated by chemical balance in-... 

Dow seawater A process for extracting magnesium from seawater. Calcined dolomite (CaOMgO, dololime), or calcined oyster shell, is added to seawater, precipitating magnesium hydroxide. This is flocculated, sedimented,... 

Koide et al. [537] have described a graphite furnace atomic absorption method for the determination of rhenium at picomolar levels in seawater and parts-per-billion levels in marine sediments, based upon the isolation of heptavalent rhenium species upon anion exchange resins. All steps are followed with 186-rhenium as a yield tracer. A crucial part of the procedure is the separation of rhenium from molybdenum, which significantly interferes with the graphite furnace detection when the Mo Re ratio is 2 or greater. The separation is accomplished through an extraction of tetraphenylarsonium perrhenate into chloroform, in which the molybdenum remains in the aqueous phase. 

In the 1990s, Pawliszyn [3] developed a rapid, simple, and solvent-free extraction technique termed solid-phase microextraction. In this technique, a fused-silica fiber is coated with a polymer that allows for fast mass transfer—both in the adsorption and desorption of analytes. SPME coupled with GC/MS has been used to detect explosive residues in seawater and sediments from Hawaii [33]. Various fibers coated with carbowax/divinylbenzene, polydimethylsiloxane/divinylbenzene, and polyacrylate are used. The SPME devices are simply immersed into the water samples. The sediment samples are first sonicated with acetonitrile, evaporated, and reconstituted in water, and then sampled by SPME. The device is then inserted into the injection port of the GC/MS system and the analytes thermally desorbed from the fiber. Various... 

Another approach consists of an in-situ acetylation and extraction of NPEOs and further analysis of the acetyl derivatives. The method has been applied to analyse effluent water and sewage sludges [102,103], sediments [104] and river waters [105]. Silylated derivatives [106] using BSA or BSTFA have also been used to determine NPEO (n < 6) in seawater [107] and wastewater [107,108], sediments [109] and sludges from wool scour effluents [110]. Halogenated derivatives of alkylphenols (AP) can also be formed as a result of chlorination practices in water treatment or wastewater if bromide is present. Brominated OPs and NPs (BrAPEOs) have been identified by GC-MS in sewage [111] and tap water [89], respectively. 

Most of the Pu in seawater is not in solution but is adsorbed on suspended sediment. When waves break at the sea surface, the spray is enriched in sediment, and in Pu, relative to the bulk seawater, by a mechanism which is the basis of the technique of froth flotation used by chemical engineers to extract small particles from aqueous suspensions. 137Cs, being in solution in the seawater, is not enriched relative to Na in the spray. 

The sediment samples used in the present study were obtained from Narragansett Bay. The sediment sample used for the PAH extraction study and in Experiments 1 and 4 was obtained adjacent to a pier in Narragansett, Rhode Island. The intercalibration sediment (ICS) was obtained near the north end of Jamestown Island (14). Recently contaminated sediments were produced by dispersing sediment obtained near the south end of Jamestown Island in seawater, dosing it with No. 2 fuel oil in a continuous flow oil-dosing system (15), and collecting it after it had settled to the bottom of the tanks. 

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