ИСТИНА

It has recently been discovered that some zooplankton organisms (viz. several taxa of sea crustaceans) accumulate trace elements like lithium, arsenic and uranium [1]. Causes and mechanisms underlying this phaenomenon are unclear. It is therefore of interest to find out which changes of chemical composition of tissues accompany the accumulation of the elements. The goal of this study was to establish correlations between analytical signals of Li, As, and U, on the one hand, and analytical signals of other elements and molecules comprising the tissues, on the other hand. To this end, atomic and molecular spectroscopy data were recorded and compared. Atomic spectroscopy was represented by laser-induced breakdown spectroscopy (LIBS) and ICP-MS with laser ablation (LA-ICP-MS). LIBS was chosen based on its rapidity and sensitivity towards light elements (like Li), while LA-ICP-MS was needed to ensure sufficient sensitivity towards As and U. The instrumentation used enabled to obtain emission spectra in a wide wavelength range (186—1049 nm). Molecular composition was studied by Raman scattering spectroscopy (excitation at 780 nm). Bulk composition data, obtained by ICP-AES and ICP-MS after digestion, were also available. Correlations between intensities of atomic emission lines, mass spectrum peaks, and parameters of Raman bands were calculated. We have also made an attempt of sample classification. All this was achieved by well-known chemometric approaches (PLS, PCR, PCA, classification tree, and ordinary LS). The results show that, in general, high level of accumulated trace elements positively correlates with a band-rich Raman spectrum with relatively low fluorescence background. Our collection of samples (ca. 30 pcs.) comprised several crustacean species, and Raman spectral fingerprints of subclass Copepoda were substantially different from those of other taxa. Apart from that, uranium content exhibited weak negative correlations with content of most other elements. Acknowledgement The reported study was funded by the RFBR according to the research project No. 18-33-01297. The collaboration between the Hungarian and Russian partners has become possible thanks to the Stipendium Hungaricum Programme of the Tempus Public Foundation (scholarship for N.S.). ICP-AES and ICP-MS elemental analyses of zooplankton samples were funded by the Russian Science Foundation (research project No. 18-77-00064). The authors are grateful to Á. Bélteki and A. Kéri for their valuable assistance. References [1] LOBUS, N.V. Elemental composition of zooplankton in the Kara Sea and the bays on the eastern side of Novaya Zemlya. Oceanology, 56 (2016), pp. 809–818.