Anthropogenic metal loads and their sources in stream sediments of the Meža River catchment area (NE Slovenia)

Abstract

Abstract The Meža River Valley has been a center of mining, ore processing and iron- and steel-based metallurgical industry for more than 300 a. This paper deals with stream sediments draining this area. Loads of potentially toxic metals and metal-bearing phases were investigated 10 a after the cessation of Pb and Zn mining. Sediments in the upper Meža River Valley show significant pollution with Pb and Zn as a consequence of mining and ore processing. The highest contents of Pb and Zn were found in the Meža tributaries, which directly drain mine waste deposits (maximum values: 19,300 mg/kg Pb and 37,900 mg/kg Zn). These results reflect transport of contaminated material from mine waste sites and indicate that the inactive mine and its mine wastes are sources of metal contamination in the surrounding environment. Contents of Cr, Ni, Cu and Co are increased in the lower Meža River Valley, in the area of Ravne, as a result of the iron and steel industry. The contribution of the Meža River to the metal-load in the Drava River is evident. Metal-bearing phases, identified in stream sediments by SEM/EDS, are assigned to three areas, according to their source and genesis. The Mežica mining district source area is characterized by ore minerals of geogenic/technogenic origin (cerussite, sphalerite, smithsonite and galena), the Ravne source area is characterized by technogenic trace metal-bearing Fe-alloys, Fe-oxides and spherical trace metal-oxides and the Meža and Drava River catchment areas are represented by geogenic metal-bearing accessory and common rock-forming minerals, such as zircon, ilmenite, rutile, sphene, barite and monazite. SEM/EDS analyses of stream sediments agree well with the results of chemical analyses and they prove to be a very useful tool for identification of metal-bearing phases and their characterization according to source and genesis.