Element enrichment factors

Figure 2.3. Elemental enrichment factors in baterial and fungi, plotted on a log scale against 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)...

Elemental enrichment factors in soils, plotted on a log scale against the ionic potential of the elements. 

To estimate the contribution of wind-blown dust of crustal origin to the fine aerosol concentration, elemental enrichment factors were calculated using the method of Macias et al. (20). The enrichment factor, EF., for an element i was calculated as follows ... 

Aerosol Elemental Enrichment Factors, 1979, China Lake... 

The present analysis uses t, the fractional elemental enrichment factor relative to the parent... 

Element Enrichment factor (relative to sea water) Element Enrichment factor (relative to sea water)... 

A common approach for identifying the enriched elements in a material is to calculate the enrichment factor (EF). The EF of an element, M, is obtained by comparing its concentration with that of a reference element, R, such as cerium or... 

Fig. 5. The log (enrichment factor) for 44 elements in Antarctic atmospheric dust compared with mean crustal concentrations.

Where c, is the concentration of an element measured at the surface, Cbt is the concentration of a stable element due to batch melting and a, is the enrichment factor due to transport. The concentrations in the melt are given by the batch melting equation. 

Uranium is not a very rare element. It is widely disseminated in nature with estimates of its average abundance in the Earth s crust varying from 2 to 4 ppm, close to that of molybdenum, tungsten, arsenic, and beryllium, but richer than such metals as bismuth, cadmium, mercury, and silver its crustal abundance is 2.7 ppm. The economically usable tenor of uranium ore deposits is about 0.2%, and hence the concentration factor needed to form economic ore deposits is about 750. In contrast, the enrichment factors needed to form usable ore deposits of common metals such as lead and chromium are as high as 3125 and 1750, respectively. 

Figure 1. Enrichment factors with respect to crustal abundances (39) for elements attached to urban aerosols from (9) Washington, D.C. (16), (O) Tucson, AZ f40j, (y,) St. Louis, MO (based on data from Loo et al. (41)),(A) Charleston, WV (42), (Ls) Portland, OR (21), and fB) Boston, MA (3,43). See Table IV, Footnote a...

Iron was chosen as the reference element because its major source is likely to be soil and it is measured with good accuracy and precision by FIXE. Crustal abundances were taken from Mason (21). Enrichment factors greater than 1 indicate an enrichment of that element relative to crustal abundances values less than 1 indicate a depletion. The results of this calculation are shown in Table 4. For this calculation it was assumed that ammonium and nitrate accounted for all aerosol nitrogen. It is seen that Si and Ca are near their crustal abundance, indicating a probable soil dust source. The low EF for Al is probably due to a systematic error in the Al measurement rather than a true depletion. Potassium, although present in small concentrations, is slightly enriched relative to crust. The other fine aerosol species, C, N, S, and Pb are enriched by factors of thousands over their natural crustal abundance, indicating that they are not due to wind-blown dust. 

Table 9.11 shows the aerodynamic mass median diameter (MMD) for some typical inorganics that are common components of tropospheric particles. Also shown are the calculated crystal enrichment factors, EFcrusl. These are a measure of the enrichment of the element in the airborne particles compared to that expected for the earth s crust, using aluminum as the reference element. Thus EF,.rust for a particular element X is defined as... 

For example, the most common elements in the earth s crust (Table 9.12 and Fig. 9.34) are O, Si, Al, Fe, Mg, Ca, Na, K, and Ti. These elements have MMDs > 3 fxva and enrichment factors that are generally less than three (Table 9.11). That the enrichment... 

TABLE 9.11 Aerodynamic Mass Median Diameters of Tropospheric Particles Containing Various Elements Observed in a Number of Studies and Enrichment Factors 1... 

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... 

In rivers and streams heavy metals are distributed between the water, colloidal material, suspended matter, and the sedimented phases. The assessment of the mechanisms of deposition and remobilization of heavy metals into and from the sediment is one task for research on the behavior of metals in river systems [IRGOLIC and MARTELL, 1985]. It was hitherto, usual to calculate enrichment factors, for instance the geoaccumulation index for sediments [MULLER, 1979 1981], to compare the properties of elements. Distribution coefficients of the metal in water and in sediment fractions were calculated for some rivers to find general aspects of the enrichment behavior of metals [FOR-STNER and MULLER, 1974]. In-situ analyses or laboratory experiments with natural material in combination with speciation techniques are another means of investigation [LANDNER, 1987 CALMANO et al., 1992], Such experiments manifest univariate dependencies for the metals and other components, for instance between different metals and nitrilotriacetic acid [FORSTNER and SALOMONS, 1991], but the interactions in natural systems are often more complex. 

Table 7.3 Crustal enrichment factors for elements from various locations using aluminium as the reference element (crustal composition data from Taylor and McLennon, 1985)...

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