Environmental Availability of Trace Metals (Mercury, Chromium and Nickel) in Soils from the Abandoned Mine Area of Merník (Eastern Slovakia)

Abstract

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≤Cr<Ni, while the extraction efficiency of individual reagents followed generally the order of HCl>CH 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<Ni. Only correlations existed between the H 2 O 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 CH 3 COOH 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

Nettle, a Long-Known Fiber Plant with New Perspectives

“…This capacity remains to be demonstrated for in situ cases. Indeed, in leaves of nettles collected in situ at contaminated sites, and levels of Cd, Cu, Hg, Ni, Pb, Zn [11,[229][230][231][232][233], and Mn [233,234] were well below the toxic levels reported by Kabata-Pendias [116]. However, TE levels in nettle roots are usually much higher than those measured in leaves (Supplementary Material Table S3).…”