The study of the ionome (ionomics) is defined as quantitative and simultaneous measurement of the element composition of living organisms and changes in this composition in response to physiological stimuli, development stage, and genetic modifications (Salt et al., Ann. Rev. Plant Biol., Vol. 59, 2008). The necessity of understanding the regulation processes of elements in the organisms demands determination of many elements in the organism, tissue, and cell (Baxter, Plant Biol., Vol. 12, 2009) . A prospect for ionomics is environmental pollution where great variety of conditions and pollutants exist resulting in concentration and interelemental changes in the plant ionome. The capabilities of and problems with several multielement analytical techniques, including instrumental neutron activation analysis (INAA), X-ray fluorescence, inductively coupled plasma-atomic emission spectrometry (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), and atomic absorption spectrometry (AAS), which are adequate and most promising in ionomic and environmental studies of plants, are reviewed. References are confined mainly to the last 10-15 years. Information about concentrations, roles, binding forms, and pollution sources of the elements and comparison between methods with respect to limits of detection, determined elements, interferences, and economic considerations are tabulated. Some combinations of instrumental techniques supplementing each other are highly valued, namely, ICP-MS and ICP-AES and INAA and AAS or ICP-AES.
While many analyses of archaeological bronzes have been reported in the literature, in practice it is very difficult to compare them. To assess the present status of the chemical analysis of bronze two ancient objects-a flat axe (arsenic bronze) and a sickle (tin bronze)-were cut into pieces weighing about 2 g each and were distributed to 11 laboratories. The participants used the following methods for analysis: INAA, ED-XRF, PIXE, TRXRF, FAAS, ICP-AES, ICP-MS, SEM-EDS, LA-ICP-MS and PGAA. The samples were analysed in at least quadruplicate. Dixon's and Iglewicz and Hoaglin's tests were used to detect outliers. The majority of methods provided comparable results, especially for macroelements, independent of the technique and standards used. The number of determined elements depended on the method and, naturally, on the concentration level. Therefore an important recommendation that can be made is to supply, with each archaeometric investigation, data from the analysis of appropriate Certified Reference Materials (CRMs) used in the study.
The formation of PGE -humic acid (HA) complexes in soil and street dust samples was investigated. In order to assess the distribution of Pt and Pd among molecular weight fractions of humic substances, the HA extracts (extracted by 0.1 mol L À 1 sodium pyrophosphate) were analysed by size exclusion chromatography coupled on-line with UV-Vis detection. Similar chromatograms were obtained for soils and street dust samples (254 nm, 280 nm) and two size fractions were operationally defined as high (1600 -5000 Da) and low molecular (51600 Da) HA fractions. The concentration of Pt and Pd in the separated extracts was determined by ICP-MS. The results indicate that up to 43% of Pt is in the high molecular and up to 52% in the low molecular HA fraction. In both type of soil samples, Pd is preferentially bound to the low molecular HA fraction. Dependence of Pd -HA and Pt -HA formation on the sample type both in the soils and in the street dust sample as well as on Pt oxidation state was established. Metallic Pt shows a tendency for complexation with the fractions of HA higher than 5 000 Da. In the street dust samples, the distribution of Pt and Pd is similar and is strongly dependent on the sample type, being bound mainly to the fractions: higher than 5 000 Da, 1600 -5000 Da and the fraction lower than 1600 Da.
The introduction of catalytic converters has led to a new environmental problem since catalysts emit platinum group elements (PGEs) which are among the least distributed elements in nature. Along with PGEs the vehicle exhaust catalysts contain also a number of stabilizers, commonly oxides of rare earth elements and alkaline earth elements such as Ce, La and Zr. Since vehicular emission of these elements has received little attention so far this work attempts to offer insight into their distribution and fate in the environment by measuring their speciation in road dust samples collected along several highways in Germany and a city centre (Saarbrücken). Speciation of the elements (fractionation into associated mineralogical phases) was carried out via a conventional sequential extraction protocol and the complexing abilities of humic substances in the organic matter were investigated by selective extraction methods in combination with size segregation. For evaluation purposes soil samples spiked with catalytic converter material were analyzed, showing a much lower fraction of Ce, La and Zr mobilized in comparison to the road dust samples. It was found that the elements were effectively bound to humic substances in road dust with a preference for complexation with low molecular weight compounds (<1600 Da).
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