Enrichment factor seawater

Figure 2.5. Elemental enrichment factors in seawater, related to the ionic potential of the elements (after Banin and Navrot, 1975. Reprinted from Science, 189, Banin A. and Navrot J., Origin of Life Clues from relations between chemical compositions of living organisms and natural environments, pp 550-551, Copyright (1975), with permission from AAAS)...

Gandon and Guegueniat [587] investigated the recovery of tin from seawater using manganese dioxide and using125 Sr as a tracer. Enrichment factors of 103 to 105 were found. 

Enrichment factor (E.F.) The degree to which a marine organism is enriched in a particular chemical with respect to the seawater concentration, e.g., E.E = [metal concentration in biogenic material]/[metal concentration in seawater]. 

Before considering the details of biological availability it is important to put this parameter in perspective. Long-term uptake is usually described by an enrichment factor equal to the ratio of concentrations of an element in an organism and in seawater. Enrichment factors for a wide range of elements in marine organisms cover orders of magnitude, from near unity for Na, Mg, Cl to 10 1 or more for phosphorus and the heavy... 

Figure 15.2. Concentrations and enrichment factors (EF) of EHCH in seawater ( ) and...

POPs level in sediments (ng.g 1 dw) POPs level in subsurface seawater (P L-1) POPs level in sea surface microlayer (pg.L-1) Enrichment factor microlayer/ subsurface ... 

We can attempt to apply the same type of model to the H2S data, however there are two additional unknown factors involved. First, we do not have a measurement of the sea surface concentrations of H2S. Second, the piston velocity of H2S is enhanced by a chemical enrichment factor which, in laboratory studies, increases the transfer rate over that expected for the unionized species alone. Balls and Liss (5Q) demonstrated that at seawater pH the HS- present in solution contributes significantly to the total transport of H S across the interface. Since the degree of enrichment is not known under field conditions, we have assumed (as an upper limit) that the transfer occurs as if all of the labile sulfide (including HS ana weakly complexed sulfide) was present as H2S. In this case, the piston velocity of H2S would be the same as that of Radon for a given wind velocity, with a small correction (a factor of 1.14) for the estimated diffusivity difference. If we then specify the piston velocity and OH concentration we could calculate the concentration of H2S in the surface waters. Using the input conditions from model run B from Figure 4a (OH = 5 x 106 molecules/cm3, Vd = 3.1 m/day) yields a sea surface sulfide concentration of approximately 0.1 nM. Figure S illustrates the diurnal profile of atmospheric H2S which results from these calculations. 

Enrichment factors (EF) were computed using aluminum and sodium as reference eelements for the earth1 s crust (4) and seawater ( 5), respectively. Enrichments were calculated by... 

Because of this behaviour, individual seawater constituents can be utilised for source apportionment studies in non-marine environments. For instance, an enrichment factor EF) for a substance X is defined as... 

The seas are a source of aerosol (i.e. small particles), which transfer to the atmosphere. These will subsequently deposit, possibly after chemical modification, either back in the sea (the major part) or on land (the minor part). Marine aerosol comprises largely unfractionated seawater, but may also contain some abnormally enriched components. One example of abnormal enrichment occurs on the eastern coast of the Irish Sea. Liquid effluents from the Sellafield nuclear fuel reprocessing plant in west Cumbria are discharged into the Irish Sea by pipeline. At one time, permitted discharges were appreciable and as a result radioisotopes such as Cs and several isotopes of plutonium have accumulated in the waters and sediments of the Irish Sea. A small fraction of these radioisotopes were carried back inland in marine aerosol and deposited predominantly in the coastal zone. While the abundance of Cs in marine aerosol was refiective only of its abundance in seawater (an enrichment factor - see Chapter 4 - of close to unity), plutonium was abnormally enriched due to selective incorporation of small suspended sediment particles in the aerosol. This has manifested itself in enrichment of plutonium in soils on the west Cumbrian coast,shown as contours of 239+240p deposition (pCi cm ) to soil in Figure 3. 

B0rsheim, K. Y., and Bratbak, G. (1987). Cell volume to cell carbon conversion factors for a bacterivorous Monas sp. Enriched from seawater. Mar. Ecol. Prog. Ser. 36, 171—175. 

Seawater abundances (from Wilson, 1975), (X)/(Na) ratios, and enrichment factors (EF) are shown [EF = (X)/(Na)acrosol/(X)/(Na)seawater], Aerosol data are from Table 7-13. h From Hoffman et al. (1974), not included in Table 7-13. 

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. 

In the analysis of seawater, isotope dilution mass spectrometry offers a more accurate and precise determination than is potentially available with other conventional techniques such as flameless AAS or ASV. Instead of using external standards measured in separate experiments, an internal standard, which is an isotopically enriched form of the same element, is added to the sample. Hence, only a ratio of the spike to the common element need be measured. The quantitative recovery necessary for the flameless atomic absorption and ASV techniques is not critical to the isotope dilution approach. This factor can become quite variable in the extraction of trace metals from the salt-laden matrix of seawater. Yield may be isotopically determined by the same experiment or by the addition of a second isotopic spike after the extraction has been completed. 

Lithium is enriched in high temperature (c. 350°C) vent fluids by a factor of 20-50 relative to seawater (Edmond et al. 1979 Von Damm 1995). The Li isotopic compositions of marine hydrothermal vent fluids ranged from MORB-like to heavier compositions (see... 

Trace metals, such as copper, nickel, cobalt, zinc, and various rare earth elements, tend to coprecipitate with or adsorb onto Fe-Mn oxides. As shown in Table 18.1, this causes these elements to be highly enriched in the hydrogenous deposits as compared to their concentrations in seawater. The degree of enrichment is dependent on various environmental factors, such as the redox history of the underlying sediments and hydrothermal activity. This makes the composition of the oxides geographically variable. 

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