Evolution of sulphide-bearing tailings from the Leşu Ursului mining sector of the Eastern Carpathians, Romania
Balaban, Sorin-Ionu; Iancu, Ovidiu Gabriel; Dill, Harald G.; Bulgariu, Dumitru; Prundeanu, Ionu Mihai
published: Apr 1, 2013
ArtNo. ESP154019003003, Price: 29.00 €
Sulphide-ore mining in the Leşu Ursului mining district, dating from approximately 1965 up to 2008, has left behind a number of tailings, which potentially constitute environmental hazards. We have investigated the topstratum (from 0 to 20 cm depth) of three of the most notable recent tailings, in an attempt to trace their geochemical and mineralogical evolution. The three tailings have different ages, the ones at Pârâul Câinelui being the oldest, followed by the Leşu Ursului – Puţul 7 tailings and the relatively recently closed Isipoaia tailings. The samples have been investigated by means of XRF for heavy metal contents, while the mineralogical composition was determined by XRD. The pH and redox potential were also determined by using the potentiometric method. The comparison of the results of the three tailings different in age illustrates that the pH has rapidly decreased during the first 5–7 years, before starting to increase towards neutral values. Simultaneously, sediment develops from a highly oxidizing to a slightly reducing environment. At the same time, the contents of Pb, Cu, As, Zn and Bi show a continuous decrease in average content, in contrast to Mn, Cr and Ni, which follow the opposite trend. For some elements such as Ga, La, Nb and Sc there was a slight increase of content with age. Regarding the major elements, our data demonstrate that the average percentages for Fe have decreased, while Al, Si, Mg, Na and K show increased concentration. The mineralogical analysis shows that jarosite and gypsum play a significant role in the youngest tailings, while they are absent in the oldest one, where ankerite and kaolinite were detected.