Source of selected potentially toxic elements in Celje children\u27s sandpits

Območje Celja je močno onesnaženo z nekaterimi potencialno toksičnimi prvinami (PTE), kot so Ba, Cu, Pb in Zn. Namen magistrske naloge je bil pregled in interpretacija stanja onesnaženosti peskovnikov in tal ob njih, primerjava vsebnosti PTE v frakciji, ki je mešanica zelo drobnega peska in melja (od 0,04 do 0,125 mm), ter v frakciji debelozrnatega melja (< 0,04 mm) in tleh. Te dve frakciji sem označila kot drobno in srednjo. Za najbolj onesnažene vzorce peska in tal sem z vrstično elektronsko mikroskopijo/energijsko disperzijsko spektroskopijo (SEM/EDS) skušala ugotoviti nosilce PTE in iz podatkov o izlužljivosti PTE podati oceno potencialne ogroženosti otrok, ki so v stiku z onesnaženimi peski in tlemi. Vsebnost PTE sem za osemnajst vzorcev peska iz peskovnikov ter za devet vzorcev tal ob najbolj onesnaženih peskovnikih izmerila z rentgensko fluorescenčno analizo (XRF). V nekaterih vzorcih sem ugotovila povišane vsebnosti Ba, Cu, Pb in Zn, ki so presegale zakonsko dovoljeno mejo. Primerjava obeh frakcij je pokazala, da je drobna frakcija bolj onesnažena, v njej pa so tudi večji razponi vsebnosti PTE. S primerjavo tal in peska sem ugotovila, da so tla bolj bogata z glavnimi oksidi, vsebujejo pa tudi močno presežene vsebnosti PTE glede na zakonsko dovoljene količine. Analiza vzorcev peska iz Puconcev ter Moravč je potrdila, da ne vsebuje kritičnih vsebnosti PTE ter da so bili le ti prinešeni v peske po njihovi menjavi. Nosilci PTE v pesku in tleh so minerali: galenit (PbS), ceruzit (PbCO3), sfalerit (ZnS), smitsonit (ZnCO3) ter barit (BaSO4), kar kaže na povezavo z mežiškim orudenjem (neustrezna menjava peska) ter na žganje rude v nekdanji Cinkarni Celje. V pesku in v večjih količinah v tleh sem našla tudi steklasta zrna žlindre s kompleksno kemično sestavo. Žlindra je nastala kot ostanek praženja sfaleritne rude v preteklosti, odložena pa je po več lokacijah v Celju in v okolici. Nosilec Fe je mineral hematit (Fe2O3), kar kaže na povezavo z železarno Štore. Ti delci so lahko bili v manjši meri prinešeni po zraku ali pa z onesnaženimi tlemi. Večina PTE je izlužjiva že v 2. fazi s šibko kislino, kar pomeni, da se le-te zelo hitro sprostijo in vežejo v rastline ter so zelo nevarne za ljudi. Najbolj so izpostavljeni otroci, ki lažje absorbirajo toksične prvine.The region of Celje is highly polluted with several potentially toxic elements (PTE) such as Ba, Cu, Pb and Zn. The purpose of the master’s thesis is to review and interpret the pollution of sandpits and nearby soil, compare the PTE-contents in the fraction, wich is a mixture of very fine sand and silt (od 0,04 do 0,125 mm) and in fraction of coarse silt (< 0,04 mm) and ground. These two fractions we labelled as fine and medium. Using scanning electron microscopy / energy dispersive x-ray spectroscopy (SEM/EDS), we attempted to determine PTE carriers and, from data on selective leaching of PTEs, provide a risk assessment for children. PTE-contents were measured using X-ray fluorescence (XRF) for 18 samples of sand from sandpits, and nine soil samples from the ground next to the most polluted sandpits. In some samples, we found elevated contents of Ba, Cu, Pb and Zn, which exceeded legal limits. Comparison of both sand fractions showed that the drobne fraction is more highly polluted, and also contains greater ranges of PTE-contents. Comparing soil and sand, we determined that soil has higher contents of main oxides, as well as greatly exceeded PTE-contents compared to legally permitted quantities. Analysis of sand samples from Puconci and Moravče confirmed that the sand does not contain critical PTE-contents, and that PTE was introduced to the sand after it was replaced. Carriers of PTE in sand and soil are minerals – galena (PbS), cerussite (PbCO3), sphalerite (ZnS), smithsonite (ZnCO3) and baryte (BaSO4) – indicating a link to the mineralisation in Mežica (inappropriate sand replacement) and smelting of ore in the former Cinkarna Celje. We also found glassy particles of slag, with complex chemical compositions, in the sand and in greater quantities in the soil. In the past, slag was formed as residue when smelting sphalerite ore, and it was deposited in multiple locations in Celje and surrounding areas. The carrier for Fe is the mineral hematite (Fe2O3), which indicates a link to the ironworks in Štore. To a lesser degree, these particles could have been transferred by air or in polluted soil. Most PTEs can be leached in the 2nd phase with a mild acid, which means that they are very easily released and binding in plants, representing a high danger for humans. Primarily for children, who are more exposed and more prone to absorb the toxic elements