Occurrence of selected trace metals and their oral bioaccessibility in urban soils of kindergartens and parks in Bratislava (Slovak Republic) as evaluated by simple in vitro digestion procedure

- First study on bioaccessibility of Cd, Cu, Hg, Pb and Zn in urban soils from Slovakia.
- Metal distribution in playground soils was dependent on the age of urban area.
- Total metal concentrations and clay content influenced the metal bioaccessibility.
- Pb isotopic data indicated a varied sources of metals in soils.

A total of eighty surface soil samples were collected from public kindergartens and urban parks in the city of Bratislava, and the <150 µm soil fraction was evaluated for total concentrations of five metals, Cd, Cu, Hg, Pb and Zn, their oral bioaccessibilities, non-carcinogenic and carcinogenic health risks to children, and lead isotopic composition. The mean metal concentrations in urban soils (0.29, 36.1, 0.13, 30.9 and 113 mg/kg for Cd, Cu, Hg, Pb and Zn, respectively) were about two times higher compared with background soil concentrations. The order of bioaccessible metal fractions determined by Simple Bioaccessibility Extraction Test was: Pb (59.9%) > Cu (43.8%) > Cd (40.8%) > Zn (33.6%) > Hg (12.8%). Variations in the bioaccessible metal fractions were mainly related to the total metal concentrations in urban soils. A relatively wide range of lead isotopic ratios in urban soils (1.1598-1.2088 for 206Pb/207Pb isotopic ratio) indicated a combination of anthropogenic and geogenic sources of metals in the soils. Lower values of 206Pb/207Pb isotopic ratio in the city centre and similar spatial distribution of total metal concentrations, together with their increasing total concentrations in soils towards the city centre, showed that traffic and coal combustion in former times were likely the major sources of soil contamination. The non-carcinogenic and carcinogenic health risks to children due to exposure to metals in kindergarten and urban park soils were low, with hazard index and cancer risk values below the threshold values at all studied sites.

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