engleski

Geochemical baseline mapping and lead pollution assessment of soils on karst in Western Croatia

The studied area follows a sharp geomorphological boundary which changes abruptly from a Mediterranean into a cold continental climate. The dominant soils are brown soils developed on limestone and melanosols developed on dolomite. Twenty five elements were analyzed in the fine soil sample fraction (-63mm) by ICP-AES after total dissolution in a mixture of concentrated acids (HF, HCl, HNO3, HClO4). The topsoil geochemical data set of both western Croatia and the national park was 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 the Risnjak national park and further to the south over the Velebit mountain. 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 fired power plants) sources, evidently occurred. With the aid of factor analysis it was possible to clearly identify areas influenced by airborne pollution. Total lead concentrations detected at latitudes 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 the influence of the amount of 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 the reference soils with presumed least anthropogenic influence from the island of Mljet (78 samples) were used. In the area of the Risnjak national park approximately 20% of samples have EF for Pb higher than 2 which can be considered as polluted while the whole region of Western Croatia (without 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).

acid rain; soils; airborne pollution; karst; geochemical baseline; lead; enrichment factor; Risnjak national park; Western Croatia

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