Geokemijsko kartiranje i procjena onečišćenja olovom tala na kršu zapadne Hrvatske

Abstract

The area studied follows the sharp geomorphological boundary at which an abrupt change occurs from a Mediterranean to a cold continental climate. The dominant soils are brown soils developed on limestone and melanosols developed on dolomite. Twenty five elements were analysed in the fine soil sample fraction (– 63 m) by ICP-AES after total dissolution in a mixture of concentrated acids (HF, HCl, HNO3, HClO4). The topsoil geochemical data sets of both western Croatia and the national park were processed through R-mode factor analysis to determine the patterns of geochemical association among elements and to detect and identify possible anomalies of elements that could be associated with airborne contamination. A four-factor model accounted for 75 % of the total variance. The association of Pb, Zn, Cd, As and P was interpreted as associated with airborne contamination and acid rain deposition. The factor score map of the Pb-Zn-Cd-As-P association shows high positive scores located along the climate boundary that passes through Risnjak National Park and further to the southeast over Mt Velebit. Along this regional climate barrier, the deposition of airborne contaminants carried by westerly winds from both regional (NE Italy) and local (Rijeka, oil refineries and oil- and coal-fired power plants) sources evidently occurred. With the aid of factor analysis it was possible clearly to identify areas influenced by airborne pollution. Total lead concentrations detected at altitudes higher than 1050 m above sea level in the national park were higher than 80 ppm (maximum 139 ppm Pb) while the regional mean Pb concentration is 43 ppm. Also a stoichiometric approach was applied to compensate for the influence of the amount of the clay fraction by modeling soil geochemical baselines on the basis of the calculation of the Pb enrichment factor (EF). As a basis for these calculations, reference soils with the presumed least anthropogenic influence from the island of Mljet (78 samples) were used. In the area of Risnjak National Park approximately 20% of the samples have an Pb EF higher than 2, which can be considered polluted, while the whole region of Western Croatia (not including Istria) has less than 3% of Pb enriched samples. All the samples from the area of Mt Velebit contain Pb within the baseline range (EF 2), što se može smatrati kao zagađenje, dok čitavo područje zapadne Hrvatske (osim Istre) ima manje od 3 % olovom obogaćenih uzoraka. Svi uzorci s područja Velebita imaju vrijednost EF za olovo unutar područja geokemijskog šuma (EF < 2) pa se može smatrati da je utjecaj atmosferskog zagađenja u tom području manje izražen