Heavy metal distribution in karst soils from Croatia and Slovakia Slobodan Miko Æ Goran Durn Æ Renata Adamcova ´ Æ Marta C ˇ ovic ´ Æ Ma ´ria Dubı ´kova ´ Rastislav Skalsky ´ Æ Sanja Kapelj Æ Franz Ottner Abstract With the use of the optimised three-step BCR sequential-extraction procedure it was possible to assess the mobility of selected elements in soil profiles from Croatian and Slovakian karst terrains. The soils in the Croatian karst were enriched in Cr, Ni, V, Mn, Cu, Cd and Mo, while soils from the Slovak Karst had high Pb and Zn concentrations. It was determined that the elements were most readily mobilised from the topsoil and the degree of mobility decreased with depth. Cr and Ni were mainly bound to the residual fraction, and Pb in the oxidisable fraction. Cu mobility was high in samples treated with agrochemicals throughout the soil profile. Keywords Karst soils Æ Heavy metals Æ Sequential extraction Æ Mobility assessment Æ Slovakia Æ Croatia Introduction Groundwater is extremely vulnerable in karst regions due to the high permeability of karst aquifers. The pollution hazards increase in industrial, agricultural and urbanised areas. Therefore, the groundwater pollution hazard is higher in Croatia, where the population in karst areas is higher than in Slovakia. However, both countries co-operate in the research of the vulnerability of the karst groundwater. The function of soil cover in groundwater protection is very important especially in karst areas. Due to the high permeability of the karst aquifers groundwater is very vulnerable in areas composed of carbonate rocks. In order to understand sealing and retention properties of soils in karst areas of Croatia and Slovakia a project entitled ‘‘Groundwater-protective effect of the soil cover in karst areas’’ was designed. Geochemical-baseline mapping and environmental studies of carbonate terrain in Croatia in the past fifteen years (Pirc and Maksimovic ´ 1985; Pirc and others 1991; Prohic ´ and others 1997; Prohic ´ and others 1998; Miko and others 1999, 2000, 2001) have shown that some areas previously considered as well preserved natural karstic landscapes have a soil cover with in general very high contents of potentially toxic elements such as Cr, Ni, Pb, Zn, Cu, Cd and Mo. Also, attempts were made by some of the authors in Croatia (Prohic ´ and others 1997, , 1998; Miko and others 1999, 2000, 2001) and in Slovakia (Bodisˇ and Rapant 2000) to calculate the enrichment factors and to apply various statistical models and normalising tech- niques in order to assess environmental impacts on the relatively thin soil cover. Since it has been widely accepted that the sole determination of total content of heavy metals is insufficient to give an evaluation of environmental im- pact, methods, which include sequential extraction, were developed to assess mobilisation and bioavailability of elements in soils. The sequential-extraction procedure is a series of single reagents used to extract operationally- defined phases from the soil in a defined sequence. The five-step Tessier protocol (Tessier 1979) has been the basis for many sequential extraction schemes performed throughout the last twenty years. More recently, the three- step sequential-extraction procedure proposed by a European working group coordinated and supported by the European Community Bureau of Reference (BCR), (Quevauviller and others 1993) has been widely applied (Thomas and others 1994; Whalley and Grant 1994; Davidson and others 1994; Sutherland 2002; Sutherland Received: 10 August 2002 / Accepted: 14 July 2003 Published online: 2 September 2003 ª Springer-Verlag 2003 S. Miko (&) Æ S. Kapelj Institute of Geology, Sachsova 2, HR-10000 Zagreb, Croatia E-mail: smiko@igi.hr G. Durn Æ M. C ˇ ovic ´ Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia R. Adamcova ´ Æ M. Dubı ´kova ´ Department of Geology of Mineral Deposits, Faculty of Natural Sciences, Comenius University, Mlynska ´ dolina G, 842 15 Bratislava, Slovak Republic R. Skalsky ´ Soil Science and Conservation Research Institute, Gagarinova 10, 827 13 Bratislava, Slovak Republic F. Ottner Department of Applied Geology, University of Bodenkultur Vienna, Peter Jordan Strasse 70, 1190 Vienna, Austria 262 Environmental Geology (2003) 45:262–272 DOI 10.1007/s00254-003-0878-y Original article