The geochemical composition of the soils and underlying sediments in the Kremna Basin was investigated. The aim was to assess whether the observed heavy metal concentrations in the soil samples represent geogenic or anthropogenic contamination.  The second objective was to show that geochem­ical data of underlying sediments should be used as a tool in the determination of  the potential hazard for soil contamination.  For this purpose,  the contents of As, Cr, Cu, Hg, Ni, Pb and Zn of soil samples were compared with standard values, a reference soil sample and local background values of the underlying sediments. The s oil samples were unpolluted regarding the contents of  As, Hg, Pb and Zn . All samples  had higher contents of Cr and Ni, whereas three samples had higher contents of Cu than the limit standard values. Geochemical parameters  showed that the higher concentrations of  Cr, Cu and Ni  in the soils could be attributed to geogenic impact. This conclusion was supported by  the Chemical Proxy of Alteration  and  Chemical Index of Weathering values , which indicated intense weathering of the sediments.  The obtained results show ed that  the Kremna area is under slight to moderate hazard if a land use change would occur, and proved the importance of the geochemical composition of under­lying sediments in the interpretation of heavy metal pollution.

compounds to oxidizing reduced inorganic compounds within the cave rocks. More importantly, the microbial diversity encountered was surprisingly high compared to what was expected given the amount and complexity of nutrients available in subterranean environments. This apparent violation of competitive exclusion or the ‘one species-one niche’ requirement (Hardin, 1960) led scientists to believe that within caves the selfish competition for resources is replaced by more cooperative and mutualistic microbial associations (Barton & Jurado, 2007). One eye-catching example of cave microbes are those found in Karstic and in lava caves which morphologically resemble white, yellow, grey, or pink bacterial colonies. Where present, these colonies can be observed throughout the cave as distinct one-millimetre INTRODUCTION