The aim of the study was the mineralogical and geochemical analysis of the sediments of the Koseze Lake, located in the northwestern part of Ljubljana. We took the core from the KS well in the middle of the lake. The core was then taken to the Department of Geology at the Faculty of Natural Sciences, where we conducted a detailed sedimentological inventory of the core and granulometric analysis of the samples. We determined that our samples belonged to three groups: slightly sandy-silty sand, very slightly silty-sandy clay, and slightly silty-clay sand. X-ray powder diffraction (XRD) was used to determine quartz, dolomite, albite, chlorite, kaolinite, gypsum, illite, and calcite in the samples studied. The clay minerals illite, chlorite and kaolinite were found in selected samples KS-20, KS-40, KS-55 and KS-65. Using a high-resolution inductively coupled plasma mass spectrometer (HR-ICP-MS), we determined the detailed elemental composition of the major oxides and heavy metals in the samples. HR-ICPMS Analysis of the oxides revealed the highest SiO2 content (43.31-74.76%), followed by Al2O3 (12.52-17.25%) and the lowest MnO (0.02-0.07%). The highest heavy metal contents show the elements Cu (273,6 mg/kg), Zn (266 mg/kg), Pb (106 mg/kg) and Cd (2,2 mg/kg). The statistical analyses have shown that the heavy metal contents decrease with depth, from which we conclude that the increased heavy metal contents are of anthropogenic origin. This is mainly due to the impact of agriculture, transport and heating. The mineralogical and elemental composition of the samples was also confirmed by electron microscopy using a scanning electron microscope with energy dispersion spectrometer (SEM-EDS). The minerals confirmed with SEM-EDS were quartz, calcite, gypsum and clay minerals. In the samples mentioned above, we also detected minerals that are potential carriers of heavy metals: zircon, ilmenite, rutile,
pyrite and REE minerals.
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