Environmental Availability of Trace Metals (Mercury, Chromium and Nickel) in Soils from the Abandoned Mine Area of Merník (Eastern Slovakia)
Edgar Hiller 1  
,   Ľubomír Jurkovič 1  
,   Juraj Majzlan 2  
,   Tatsiana Kulikova 1  
,   Tomáš Faragó 1  
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Department of Geochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, 842 15 Bratislava, Slovak Republic
Institute of Geosciences, Burgweg 11, Friedrich-Schiller University, 07749 Jena, Germany
Edgar Hiller   

Department of Geochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, 842 15, Bratislava, Slovak Republic
Submission date: 2020-12-03
Final revision date: 2021-02-23
Acceptance date: 2021-02-26
Online publication date: 2021-08-31
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 (CH3COOH) 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≤CrCH3COOH ≈ EDTA>˃H2O. 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<Ni. Only correlations existed between the H2O extractable metal concentrations and the plant root concentrations. Bioconcentration factor (BCF) and translocation factor (TF) were considerably lower than 1.0, while BCF values for Ni were sensitive to soil pH, with higher values in more acid soils. The plant availability of Hg and Cr was by one order of magnitude lower than that of Ni, indicating that the former mine area poses no serious environmental and health risks, despite high metal concentrations in soil. Higher plant availability of Ni compared to Hg and Cr was likely due to high Ni solubility in CH3COOH and EDTA solutions (10.3±5.51% and 9.39±4.50% of the total soil concentration, respectively), which release the metals present in exchangeable form, carbonate bound and complexed with soil organic matter. Low Hg availability could be explained by its binding to stable cinnabar(metacinnabar) as indicated by extended X-ray absorption fine structure (EXAFS) and μ-X-ray fluorescence (μ-XRF).