engleski

Geochemical anomalies in stream sediments of the upper Sava River drainage basin (Croatia, Slovenia), determined by statistical methods

Introduction Sava River is a transboundary river of supraregional interest, draining 95, 719 km2 in Slovenia, Croatia, Bosnia and Herzegovina and Serbia. It is a typical Alpine river, flowing from Julian Alps. It becomes a typically lowland river when entering Croatia. The upper flow of Sava River can be compared with Soča/Isonzo River, which flows from the other side of Julian Alps toward Adriatic Sea. The aim of the work was to extend the mineralogical and geochemical dataset of stream sediments from Upper Sava River and to study the possible influence of sub-basins of Savinja, Krka and Kupa rivers on main course of Sava River. Methods Mineral composition was determined by X-ray diffraction and chemical composition by inductively coupled plasma mass spectroscopy (ICP-MS). Two different procedures to identify anomalous geochemical data were used: the box plot method and the median absolute deviation (MAD). Results and discussion Results obtained by the box plot method showed that anomalous concentrations (extreme or outlier) of Zn, Pb, In, Cu, Co, Se, Zr, Cd, As, K, Na, Tl, Ba, B, Mn, Fe are present in sediments of the Celje region, of Cr, Ni, S, In, Cu, Mo, Pb in Moste Dam (pollution traced down to camping Šobec), and of Hg in Litija-Zagorje mining region. The MAD method is more sensitive. It depicts the same polluted areas, but with more anomalous values, which are above threshold values for toxicity. Both statistical methods (box plot and MAD) show two anomalous values for Hg in Sava River near Kranj and Zagorje. The concentrations are much higher than those causing significant toxic effects (>2 ppm). The two locations of Sava River in Croatia show very clean environment with respect to trace elements, although Sava River passed big cities of Zagreb and Sisak. The results clearly indicate selfpurification mechanisms of Sava River. Recommendations and perspectives Similar future sediment study is recommended on middle and lower Sava drainage basin of interest for Croatia, Bosnia and Herzegovina and Serbia to detect possible pollution centers. In the case of significant pollution, remediation of sediments and watershed management should be applied.

Sava River; sediments; box plot method; MAD method; anomalies; pollution detection

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