engleski

A combined multi-instrumental approach for the physico-chemical characterization of stream sediments, as an aid to environmental monitoring and pollution assessment

In the present study we aimed to show on selected sedi-ments from Kupa drainage basin, the advantages of using combined multi-instrumental approach in physico-chemical assessment of sediment quality, with respect to inorganic pollutants. Mössbauer spectroscopy and solid-state magic angel spin nuclear magnetic resonance (27Al and 29Si MAS NMR) methods are recommended in addition to commonly applied techniques: X-ray diffraction (XRD), inductively coupled plasma mass spectroscopy (ICP-MS), X-ray fluo-rescence(XRF) and grain size analysis, to characterize in details stream sediments. It is suggested that the applica-tion of physico-chemical methods, together with a detailed characterization of Fe and Al minerals, is useful in geo-chemical approach, which is complementary to biological and toxicological tests in TRIAD approach. From the difference in concentrations of pollutants de-termined by non destructive XRF and destructive ICP-MS (in aqua regia extract), it is possible to distinguish firmly bound elements: Cr (46-95%), As (84-97%), Pb (29-92%) from loosely bound element Mn (0-8%), which were in some cases above the level causing significant toxicity. The difference is given in percentage as relative scale. XRD method is useful to determine mineralogical composition of sediment samples. Mössbauer spectroscopy and solid state NMR methods can be used for poorly crys-talline and amorphous phases. Quantitative information about the relative population of the iron species together with specific properties of the individual iron sites as oxida-tion states, and possible iron minerals were obtained by Mössbauer spectroscopy. In the studied samples, the pres-ence and the ratio of tetrahedral and octahedral Al were determined by solid state 27Al MAS NMR. From chemi-cal shifts in comparison with reference spectra of minerals some aluminosilicates (muscovite and kaolinite) were con-firmed by solid state 29Si and 27Al MAS NMR methods. It is recommended that whenever possible it is better to use the two methods (Mössbauer spectroscopy and NMR) in sediment analysis. These methods can be used to follow changes in Fe3+/Fe2+ ratio and changes in Al coordination, which are significant in evaluation of precipitation and dissolution processes, which effect pollutant distribution. Multi-methodical approach on sediments is recom-mended in the initial phase aimed at identifying minerals which can be useful sinks for pollutants that may pose risks for ecosystems.

multi-instrumental approach; stream sediments; physico-chemical characterization; pollution assessment; environmental monitoring

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