engleski

Evaluation of terra rossa geochemical baselines from Croatian karst regions

In karst regions of Croatia regolith is the only favourable medium for geochemical mapping. Mediterranean climate and good drainage due to hard, fissured, permeable limestones and dolomites resulted in a frequent and spacious distribution of terra rossa (FAO-luvisols and cambisols) -a polygenetic type of soil. Samples of terra rossa from coastal and inland Croatian dinaric karst terrains were collected during the initial studies for the Geochemical Map of Croatia at a density of 1 site/25 km2. A total of 103 terra rossa samples taken from the depth of 5-25cm together with 29 samples from deeper profiles (down to the depth 850 cm) were analysed for total Al, Ba, Ca, Co, Cr, Cu, Fe, Ga, La, Mg, Mn, Ni, Pb, Na, Sr, Ti, V and Zn concentrations. A stoichiometric approach was applied by modelling of terra rossa baselines on the basis of linear regressions of metals on Al and the calculation of enrichment factors (EF and CEFs) on the basis of soil standards. A noticeable enrichment of Pb was found in surface samples compared to the terra rossa of deeper in the soil profile. Using these baseline relationships, an attempt is made to partition terra rossa metal concentrations into natural and anthropogenic fractions. Also the models from both polluted and less polluted (uninhabited) karst terrains improve the comparability of element contents through correction of variable background concentrations. Comparison of elemental concentrations revealed that that due to contributions of bauxite debris a number studied samples is enriched in Cr and Ni (also with variable amounts of boehmite). The corrections will serve to reduce data variability and to increase the detection of spatial and temporal differences presented on the geochemical maps.

terra rossa; geochemical baselines; enrichment factors; Croatian dinaric karst

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