engleski

Topsoil geochemistry as a consequence of acid rain deposition at an abrupt climate boundary, the case of National Park "Risnjak", Croatia

The Risnjak national park lies on a sharp climatic boundary which changes abruptly from a Mediterranean into a cold continental climate with acid rain (pH < 5.6) deposition predominating through the year. The park lies in the high (900m-1560 m above sea level) mountain karst region of western Croatia, approx. 30 km from the port and industrial city of Rijeka. The dominant topsoil cover are brown soils developed on limestone and melanosols developed on dolomite. Twenty five elements were analyzed in the fine soil sample fraction (-63*m) by ICP-AES after total dissolution in a mixture of concentrated mineral 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 paterns 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 integrated with slope analysis and processed through GIS, 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 (max. conc. 139 ppm Pb) while the regional mean Pb concentration is 43 ppm. The amount of elements associated with the acetic acid (1 M NaOAc, pH=5) soluble fraction was below 10% for Zn, Al, and Cu, while 23 % in average for Pb (range 3-50%).

Acid rain; Soils; Airborne pollution; Karst; Climate boundary; Lead; Western Croatia

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