Celje and its wider surroundings are burdened by potentially toxic elements (PTEs) due to past industrial activities, to which children are particularly vulnerable. In the past, elevated levels of PTEs have been detected in some sandboxes. At selected sandbox sites in the Celje Basin, we repeated the monitoring of sand and nearby soils and compared the results with those of older studies. Isotopic analyses of lead, zinc, strontium and iron were carried out to identify potential sources of contamination. In the sandboxes, the fraction <0.04 mm (<1%) and the fraction 0.125-0.04 mm (<10%) decreased. The 1-0.125 mm fraction dominates: between 74 % and 95 %. Higher CaO and MgO contents were detected in two of the sandpits, also indicating that the Mežica Valley mine waste material was used in the past as gravel for the embankment sandboxes. Soil samples still contain elevated levels of PTEs (mainly As, Ba, Pb and Zn), critical and warning values for Ba, Cd, Cr, Pb and Zn are exceeded in some sandpits, and the limit values for As and Mo are also exceeded. Using the isotopic ratios 87Sr/86Sr, δ66ZnJMC, δ68Zn, δ 56Fe and δ 57/54Fe, we found that at all sites the isotopic composition of the soil and sand samples partially matched the isotopic composition of the samples of the mine waste from the Pb-Zn mine in Mežica and the slag from Celje (the old Cinkarna Celje). The 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, 208Pb/207Pb, 207Pb/206Pb ratios indicate a greater similarity to the Mežica mine waste samples. It is most likely that the PTE contamination of the sandboxes and nearby soils is due to a combination of different sources: both the mine waste from Mežica, the slag from Celje and other unidentified sources.
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