Enrichment of trace metal

The surface layer composition may effect catalytic activity. Surface enrichments of trace metals, for example, may enhance the catalytic role of particles in heterogeneous reactions in the atmosphere involving gaseous pollutants such as SO2 (54, 55). 

Vanderborght, B. M., van Grieken, R. E. Enrichment of trace metals in water by adsorption on activated carbon. Anal. Chem. 49, 311 (1977)... 

The process of enrichment of trace metals in these non-biologically produced sediments is probably adsorption to the surface of iron and manganese oxides that form on virtually all particle surfaces in the ocean. This is also the process that forms manganese nodules in vast areas of deep-ocean sediments. Manganese nodules actually accrete on the sea floor at a rate of approximately 1 mm per million years, primarily in areas where there is little accumulation of CaCOs and opal-rich sediments, e.g. the vast red clay provinces of the North Pacific Ocean. Manganese nodules are enriched in the same metals that are found authigenically in the sediments (Table 12.4) to such an extreme... 

Using empirical orthogonal functions (Dippner and Pohl, 2004) for a monitoring data set for the period 1993-2000 a positive trend in the order of one-third standard deviation appeared for dissolved Cd and Cu concentrations in surface waters of the B altic Proper. It was discussed that these trends were a result of a new stagnation period when the exchange with North Sea water was limited and the trace metal input via atmospheric and riverine sources resulted in the enrichment of trace metals in surface waters. This assumption was supported by the pollution loads entering the Baltic via rivers, industries, urban areas, and from the atmosphere (Table 13.2). 

Savanna ecosystems contain niobium 11 times, beryllium and molybdenum 6 times, and titanium and zirconium 4 times as high as compared to the respective crustal concentrations (darks) of these metals. In the Ugandan soils, the chromium content is 7 times higher than dark value and that of copper, 5 times. Such a large difference in soil enrichment of trace metals is related to their different input into biogeochernical cycles of corresponding ecosystems. 

Schuster, M. Selective complexing agents for the trace enrichment of platinum metals. Fresenius J. Anal. Chem. 1992, 342, 791-794. 

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. 

An ideal method for the preconcentration of trace metals from natural waters should have the following characteristics it should simultaneously allow isolation of the analyte from the matrix and yield an appropriate enrichment factor it should be a simple process, requiring the introduction of few reagents in order to minimise contamination, hence producing a low sample blank and a correspondingly lower detection limit and it should produce a final solution that is readily matrix-matched with solutions of the analytical calibration method. 

Thns after the Cambrian explosion in novel trophic chains with now >2 trophic levels the issnes of nntrient transfer and cycling, inclnding that of trace metals, became prominent even now, there are no essential metals which nndergo consistent, step-by-step enrichment within limnetic trophic chains (Franzle and Markert 2002), the only metal to do so from phytoplankton via zooplankton eventnally to piscivorons fishes being niobinm. In addition, the shift from nni- to multicellular top-level consumers implied cell-type... 

In the fractionation process, the minor components of the original oil become concentrated in the separated fractions. This concentration has a considerable effect on the oxidative stability of the individual fractions. Relative to the starting oil, the liquid or soft fraction is enriched in tocopherols and depleted of trace metals. The reverse occurs with the hard or stearine fraction, which becomes appreciably more susceptible to oxidation despite its lower content of unsaturates. The stearine fraction is also the recipient of other impurities remaining in the oil after rehning and bleaching, such as phosphatides and soap. 

Ndung u K, Djane N-K, and Mathiasson L. Determination of trace metal ions in river water by ion-pair chromatography after enrichment using supported liquid membrane. J. Chromatogr. A 1998 826 103-108. 

Schulek, E, Remport-Homth, Z., Laszity, A., Koros, E. Enrichment of traces of metals on carboxycellulose cation exchanger. Magy. Kem. Foly. 75, 58 (1969) Anal. Abstr. 18, 4470 (1970)... 

When a small-bore column, such as 0.5 mm i.d., was used, aU peaks appeared simultaneously if the volume of the retained stationary phase was over 15%. However, if the retention volume of the stationary phase was less than 10% in a small-bore column, peak separation was observed as shown in Fig. 5. " Each peak was detected by plasma atomic emission spectrometry. This peak profile shows enrichment profiles with separation of Mg, Cu, Mn, and Ca in tap water. The intensity of Ca is shown in the right axis, 3 orders higher than that of the other elements, while the intensity of Mn is amplified 10 times. The spectral interference of Ca to the signal of Cu is observed. This separation phenomenon is considered to be quite useful for exact determination of trace metals. 

In addition to the above direct contributions of microoi anisms to the formation of ferromanganese nodules, several indirect contributions may also be possible, and may indeed be essential to the formation of extensive ferromanganese deposits, especially those highly enriched in trace metals other th2in iron and manganese. For example, the most extensive deposit of... 

The concentration of trace metals by volcanic input, by the reflux of hypersaline waters, or by other extraordinary metallic ion enrichment of the Phosphoria sea are not required according to data and interpretations given by Calvert (30 p. 201-212). 

The enrichment of trace elements in iron-manganese crusts and nodules is well-known and has been described, for example, by Hlawatsch et al. (2002), Marcus et al. (2004), Kersten and Kulik (2005). Besides the diffusion from the underlying sediments, the main pait of trace elements in crusts is derived from their dissolved forms in sea water. Even if the accumulation process is natural, the available amount of dissolved heavy metals is affected... 

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