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In this study, playground soils of kindergartens and green recreational zones in Bratislava were investigated for the occurrence and gastric bioaccessibility of arsenic (As) in the < 150 μm soil size fraction. Eighty topsoil (0-10 cm) samples were collected from playgrounds in kindergartens and green recreational zones throughout the urban area. Bioaccessibility measurements of As were performed using the Simple Bioaccessibility Extraction Test that mimics the human gastric environment, and resulting extracts were analyzed by hydride generation-atomic absorption spectrometry to assess bioaccessible As concentrations in the collected playground soils. Single selective chemical extractions using hydroxylamine hydrochloride-hydrochloric acid and dithionite-citrate-bicarbonate solutions also were used to determine the amount of As associated with amorphous and amorphous/crystalline Fe oxy-hydroxides in soils, respectively. The results showed that the spatial distribution of total As concentrations was related to the historical development of the city, with higher soil concentrations of As found in the old city centre and related urban zones and the lower ones on the outskirts of Bratislava. There was a variation in the values of bioaccessible concentrations and fractions of As, with ranges from 0.40 to 5.60 mg/kg and 7.29 to 56.1%, respectively. Correlation and multivariable linear regression analyses revealed that bioaccessible concentrations of As were linearly related to its total concentrations in the soils, whereas dithionite-citrate-bicarbonate extractable Fe (Fe) was the main soil property, controlling the bioaccessibility of As. When the amount of Fe in the soils increased, As bioaccessibility decreased, confirming an importance of Fe bound to amorphous and crystalline iron oxy-hydroxides to the limitation of As bioaccessibility in urban playground soils of Bratislava. Additionally, single selective extractions showed that As concentrations extracted by hydroxylamine hydrochloride (As) and dithionite-citrate-bicarbonate (As) were positively correlated with its bioaccessible concentrations (Spearman r = 0.75 and 0.62, respectively; p < 0.001).

The former mercury ore deposit of Merník in Eastern Slovakia was selected for the investigation of the environmental availability of mercury (Hg), chromium (Cr) and nickel (Ni) in mine soils. Singlestep extractions with four chemical agents (deionised water, ethylenediaminetetraacetic (EDTA), acetic (CH 3 COOH) and hydrochloric (HCl) acid solutions) and chemical analysis of the common nettle (Urtica dioica) were used to determine the availability of the three metals. Regardless of the type of extraction, the soluble ratios of metals in mine soils increased in the order of Hg≤CrCH 3 COOH ≈ EDTA>˃H 2 O. The total or extractable metal concentrations in soil did not correlate with their concentrations in aerial parts of the common nettle, however, its ability to accumulate these trace metals in roots and aerial parts copied the results of extraction tests, i.e. Hg≤Cr