| الوصف: |
Namen raziskave je bil ugotoviti mineralno in geokemično sestavo vzorcev sedimenta Koseškega bajerja, ki se nahaja na severozahodnem delu Ljubljanske kotline. Iz sredine jezera smo odvzeli jedro vrtine KS in naredili natančen sedimentološki popis jedra, granulometrijsko analizo vzorcev ter pripravili vzorce za nadaljnje raziskave. Ugotovili smo, da naši vzorci pripadajo trem skupinam: malo peščen meljast pesek, zelo malo meljasta peščena glina in malo meljast glinen pesek. Z rentgensko praškovno difrakcijo (XRD) smo v obravnavanih vzorcih določili kremen, dolomit, albit, sadro, illit in kalcit. V izbranih vzorcih KS-20, KS-40, KS-55 in KS-65 smo našli glinene minerale illit, klorit in kaolinit. Z visoko ločljivostnim masnim spektrometrom z induktivno sklopljeno plazmo (HR-ICP-MS) smo v vzorcih določili detajlno elementno sestavo glavnih oksidov in težkih kovin. V vzorčni vrtini smo našli največjo vsebnost SiO2 (43,31–74,76 %), kateri sledi Al2O3 (12,52–17,25 %), najmanj pa je MnO (0,02–0,07 %). Najvišje vsebnosti težkih kovin, pripadajo elementom Cu (273,6 mg/kg), Zn (266 mg/kg), Pb (106,8 mg/kg) in Cd (2,2 mg/kg), najnižje vsebnosti pa elementom Sb (0,6 mg/kg), As (14,6 mg/kg), Mo (4,7 mg/kg) in Ni 36(mg/kg). Z statističnimi analizami smo dokazali, da se vsebnosti težkih kovin z globino znižujejo, posledično lahko sklepamo, da so v zgornjih cm jedra zvišane vsebnosti težkih kovin antropogenega izvora. Gre predvsem za vpliv kmetijstva, prometa in kurjave. Mineraloško in elementno sestavo vzorcev smo potrdili tudi z uporabo elektronske mikroskopije, in sicer z vrstičnim elektronskim mikroskopom s spektrometrom energijske disperzije (SEM-EDS). Potrdili smo naslednje minerale: kremen, kalcit, sadro in glinene minerale. V omenjenih vzorcih pa smo zaznali minerale, ki lahko veljajo kot potencialni nosilci težkih kovin: cirkon, ilmenit, rutil, pirit in minerali REE. 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. |
