Koncentracija Cd, Pb in Zn v tleh po sanaciji z zamenjavo vrhnjega sloja tal

V diplomskem delu smo preverili uspešnost sanacije/preplastitve otroškega igrišča Polena v Mežici, ki je bilo zaradi kritičnih imisijskih vrednosti Cd, Pb in Zn sanirano leta 2008. Z meritvami vsebnosti kovin smo preverili debelino pokrivnega sloja. Odvzem vzorcev smo izvedli z žlebasto sondo tako, da smo zajeli celotno površino igrišča. Ugotovili smo, da je plast zemlje različne debeline, od 10–90 cm, in na izgled heterogene sestave. Vrednosti koncentracij Cd, Pb in Zn smo na terenu izmerili z metodo rentgenske fluorscenčne spektrometrije (XRF). Z enako metodo smo izvedli tudi meritve suhih vzorcev v laboratoriju. Za primerjavo smo opravili tudi meritve kovin po kislinskem razklopu talnih vzorcev z zlatotopko. Izmerjeni povprečni koncentraciji Pb in Zn v vrhnjem sloju tal sta presegali kritično imisijsko vrednost, izmerjena povprečna koncentracija Cd pa je presegala opozorilno imisijsko vrednost. Izmerjene vrednosti koncentracije Cd na posameznih lokacijah odvzema vzorcev so se v vseh slojih gibale v velikem razponu (v sloju od 15–20 cm v razponu od 8 mg/kg do 223 mg/kg). V velikem razponu so se gibale tudi izmerjene vrednosti koncentracije Pb (v sloju od 25–30 cm v razponu od 296 mg/kg do 30.323 mg/kg) in Zn (v sloju od 15–20 cm v razponu od 549 mg/kg do 10.484 mg/kg). Potrdili smo veliko horizontalno variabilnost koncentracije kovin Cd, Pb in Zn, kar dokazuje neenakomerno izvedbo preplastitve. Rezultati neposrednih terenskih meritev koncentracije Cd, Pb in Zn v tleh z uporabo XRF metode so se statistično pomembno razlikovali od meritev suhih vzrorcev z XRF metodo v laboratoriju. Statistično značilno so se razlikovali tudi rezultati meritev koncentracije z uporabo XRF metode v laboratoriju z rezultati meritev po kislinskem razklopu tal. Večina rezultatov meritev po kislinskem razklopu je pokazala manjše vrednosti, največja razlika je bila pri meritvah koncentracije Pb. This diploma thesis examined the efficiency of the remediation of the children’s playground “Polena” in Mežica. Due to the critical immission values of Cd, Pb and Zn, this playground was restored in 2008 by replacement/overlaying surface soil layer. The thickness of the covering soil layer was determined by measuring the content of the metals. Soil samples were taken on 23 sites using the gouge auger. We found that the soil of the playground is very heterogeneous, the thickness varying from 10–90 cm. The concentrations of Cd, Pb and Zn were measured on the field using portable X-ray fluorescent spectrometer (XRF). The same method (XRF spectrometry) was used in the laboratory for measurement of dry soil samples. Results were comparable with measurements after dissolution of soil samples in aqua regia. The measured average concentrations of Pb and Zn in the top soil layer were above the critical immission value, the measured average concentration of Cd was above the warning immission value according to the Slovenina legislation. We confirmed a great horizontal variability of the metal concentration, which proves an uneven overlayering. The concentration of Cd on individual sites varied considerably (in the layer from 15 to 20 cm, the range was from 8 mg/kg to 223 mg/kg). The concentration of Pb also varied considerably (in the layer from 25 to 30 cm, the range was from 296 mg/kg to 30.323 mg/kg). The concentration of Zn also varied noticeably (in the layer from 15 to 20 cm, the range was from 549 mg/kg to 10.484 mg/kg). The results of the measurements of Cd, Pb and Zn in the field (moist samples) by using XRF method were statistically different from the results obtained from measurements of dry samples in the laboratory. The concentration of metals determined after aqua regia dissolution was statistically different (mostly lower values) from the results of XRF method, the biggest difference occurring for the measurements of Pb.