engleski

Vulnerability of karst area related to potentially toxic elements

Soil samples from the Una river spring catchment (32 locations) were analysed. Soil chemical analyses as well as chemical extraction analyses were carried out on the samples. The data were used to present distribution maps of potentially toxic elements (Al, Cu, Mn, Pb and Zn) in the surface soil of the Una river spring catchment. To evaluate the vulnerability of the immediate spring zone of the karst catchment, the vulnerability map was derived from the application of the PI methodology proposed by the European COST Action 620. The PI method used for making of the vulnerability map takes into account the protective cover (P) and the infiltration conditions (I). It is based on the origin- pathway-target model. The π-factor describes the vulnerability map and is divided into 5 classes. π-factor from 0-1 implies the area of the extreme vulnerability, while π-factor from 4-5 implies the area of the very low vulnerability. It is the product of P and I ; π = P x I. In order to be able to compute the P factor (protective cover), the information about protective function of all layers are needed (top soil thickness as well as the sub soil thickness), precipitation regime, grain size, lithology, fissuring and karstification. The extraction procedure for elements Al, Cu, Mn, Pb and Zn, has been applied in order to determine the redistribution and the potential mobility of elements that could have influence on the groundwater and could affect its quality. The applied extraction was the first step of the sequential procedure proposed by Tessier et al., (1979), i.e. extraction with 1 mol dm-3 CH3COONa/ CH3COOH buffer (pH 5). Lead shows the highest mobility content, with mean of 9% (max. 16%) extracted in an acidic condition. Manganese follows with mean of 5% (max. 11%) in addition to zinc, copper and aluminium with less than 1% (mean) of mobile content. The results of this study provide the information on the potential mobility of the studied elements, indicating the possibility of their mobilization through changes in pH. The vulnerability map of the karst area was made in order to predict protection of karst aquifers. The studied researched Una spring catchment area has the low and moderate vulnerability in most parts, and 8 % of the studied area can be considered as extremely vulnerable according to the PI-methodology.

Karst area vulnerability map; PI-method; soil; environmental geochemistry; River Una

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