Experimental study of As elimination from the pit water in locality Zlatá Idka-Rieka, Slovakia and characterization of sediment in this locality

The study presents introductory laboratory and in-situ experiments focused on elimination of As from the pit water in locality Zlatá Idka-Rieka, Slovakia, as well as on characterization of the sediment parameters in this locality from the viewpoint of their eventual toxicity. The mobility of As from the sediment is dependent on the chemical bonds with non-stable Fe oxides/hydroxides, creating surface coatings on the grains of minerals and soil, present in the lake of pit water. Leachates after the Simply Bioavailability Extraction Test contained high concentrations of Fe (223 mg.l–1), Mn (165 mg.l–1), as well as As (11.1 mg.l–1), which are potential toxic for people in case of contamination of the soil attached to vegetables, or from coarse dust that can be inhaled and then swallowed. The batch adsorption experiments were performed in the laboratory and next in in-situ conditions. As adsorbents natural zeolite, terra rossa and their mixture were used. In laboratory the As adsorption was fast, reached equilibrium almost after 4 hours. The adsorption capacity of zeolite and terra rossa was 18.3 and 25,3 μg.g–1, respectively. Effect of in-situ As removal was the highest for terra rossa (almost 85 %) and the concentration of As in leachate after the experiment was slightly higher than required limited value. The promising results for future in-situ applications brought laboratory column experiments, where after 4 cycles of adsorption the effectivity of columns was still 95 % independently on the columns filling (layers or mixture of studied adsorbents).