ENVIRONMENTAL CONTAMINATION BY HEAVY METALS IN REGION WITH PREVIOUS MINING ACTIVITY

Extreme use of raw materials and their processing dramatically increases the loading of all environmental components by heavy metals, which is then reflected in also in the human health. At present there are 7 environmentally loaded areas in Slovakia. In this study the north part of Volovske Mountains is monitored which is located between two major emission sources of Rudniansky loaded region. Iron ore mines in Rudnany was in the past the most important source of Hg (in 1978-1979 over 4000 kg Hg were emitted into the atmosphere per year) due to the mining of Cu and Fe ore. Smelter factory Krompachy with the previous copper production is another major emission source in this region. Studied area is also characterized by geochemical anomalies. The study is focused on determination of the loading level of forest ecosystems by Zn, Cd, Cu, Pb, Hg originated from iron-ore mines Rudnany and smelter factory Krompachy. In the investigated area of about 156 km2 samples of forest soil and vegetation from 45 predetermined sampling sites were collected. In soil samples the exchangeable soil reaction, content of humus and heavy metals were determined (total content of heavy metals - in soil extract by aqua regia, mobile forms of heavy metals - in soil extract by NH4NO3, c = 1 mol/dm3). Samples of plant material (permanent grassland) were mineralized by microwave decomposition. Content of heavy metals in soil and plant material was determined using by AAS method. The threshold values proposed by Directive 86/278/EEC were exceeded for total soil content for Zn (Cd, Pb, Hg and Cu, resp.) in 26 (44, 18, 42 and 19, resp.) sampling sites. In terms of ecotoxicity Hg is the most risky metal.