THE GEOCHEMICAL DISTRIBUTION OF HEAVY METALS FOR SOME MINE TAILINGS FROM THE FUNDU MOLDOVEI AREA, ROMANIA

The objectives of the present study were (i) to determine the contents of heavy metals (Cr, Cu, Mn, Zn, Cd, Pb, Co, As, Ni and Fe) from tailings samples which had previously been dissolved with HNO3 and concentrated HClO4, (ii) to determine the pH of the samples in both aqueous and saline suspensions, (iii) to determine the Eh of the samples, and (iv) to calculate the correlation factors between the heavy metal concentration values and the pH and Eh values. The study was conducted on a series of 31 samples, collected from three mine tailings (MT) locations in the Fundu Moldovei area (Dealu Negru and, for the comparison of values, Prasca I and Prasca II). The concentrations of heavy metals were determined by means of Atomic Absorption Spectrometry, after having previously treated the samples with HNO3 and concentrated HClO4. The pH was determined through the potentiometric method, in both aqueous and saline solution. The data obtained was summed up and projected onto concentration maps and 3D distribution diagrams, both for each minor element, and for the pH and Eh. The concentration maps and 3D diagrams were built by using Golden Software's Surfer 9.7.543 and Visual Basic scripts applied to it. The approximated 3D surface of the mine tailings was obtained, through the same software, only in the case of the Dealu Negru MT, while the other 2 mine tailings deposits were used only in order to compare the values of heavy metal concentrations, pH and Eh. The results have shown that, in case of the Dealu Negru MT, there is a clear discrepancy between the contents of heavy metals from the samples gathered from the top of the mine tailings deposit and the ones collected from the bottom. A possible explanation for this phenomenon would be the presence of a draining pool on top of the Dealu Negru MT, draining pool which was dried out some 5 years ago. For the Dealu Negru MT, the pH values determined in aqueous solution ranged from 2.45 to 5.25, while the Eh ranged from 0.247 V to 0.390 V. For the Prasca II MT, the pH determined in aqueous solution ranged from 3.44 to 4.60, and the Eh ranged from 0.340 V to 0.412 V, while in case of the Prasca I MT, the pH values determined in aqueous solution ranged from 3.73 to 5.12, and the Eh values ranged from 0.280 V to 0.405 V.