engleski

Distribution of some elements in topsoil developed on alluvial sediments of the Drava and Sava Rivers in nothern Part of Croatia

For the purpose of the Geochemical map in Northern part of Croatia the soil samples were collected at a depth down to 25 cm in a quadratic grid 5x5 km. The analytical work (ICP-AES and FAAS for Hg) was performed on the granulometric fraction <0.063 mm. The precision and accuracy were satisfactory for all analyzed elements. In soils developed on alluvial sediments of the Sava and Drava rivers there is an increasing of element concentrations downstream. The cluster analysis of raw data indicates the presence of three groups of elements with similar distribution: 1) PHES (As, (Cu), Hg, Pb & Zn) ; 2) other heavy metals (Co, Cr, (Cu), Fe, Ni & V) ; and 3) elements associated with carbonates (Ca and Mg) (for Ca & Mg r=0.93 significant at p<0.05, n=87). Increased values for Ca and Mg in soils developed on alluvial sediments of the Sava River between the Sava and Sutla and the Sava and Kupa Rivers confluences and their high correlation coefficients indicate carbonate origin of alluvial sediments transported from the Alps. High concentrations of Hg and Pb in the Sava River soils are a consequence of mining activities in Litija (Slovenia) (Mlakar, 1994) and of urban contamination of Zagreb (traffic, industry etc.) (Namjesnik et al., 1992). The enrichment of sediments with other heavy metals is a consequence of usage of agriculture-fertilizers (Zn and Cu), vineyards-bactericides and fungicides (Cu) (Adriano, 1986) and historical mining in surrounding mountains (Pb and Zn). After the Kupa and the Sava River confluence the soils above the alluvial sediments have increased concentrations of PHES (except Hg) and other heavy metals and decreased concentrations Ca and Mg. The anthropogenic input originates from the Sisak&#8217; s industry. The content of Hg is decreasing downstream and is connected with dilution of the Sava River sediments by the Kupa River alluvial deposits. The slight positive trend of PHES is after the Una and the Sava Rivers confluence. Decreasing of other heavy metal contents could be a consequence of decreased influence of Sisak&#8217; s industry. Increasing of concentrations of Ca and Mg in soils developed on alluvial sediments after the confluence of the Sava and the Una River is the consequence of income of Miocene, mostly carbonate, clastic material by the Una River. Alluvial sediments of the Sava River after the income of alluvial sediments by the Vrbas River have lower concentrations of Hg, Ca and Mg, and higher concentrations of other heavy metals. The application of cluster analysis shows the common source of Zn, Cu and Pb. An expressive enrichment of their concentrations and concentrations of other heavy metals emphasises an arising influence of material from the Central Ophiolite Zone. The Drava River alluvial sediments have higher concentrations of Pb, Zn and As in relation to other investigated areas in NW Croatia (Miko et al., 2001). The mud particles in the water suspension of the Drava River are highly loaded with anthropogenic Pb and Zn as a consequence of mining, smelting and flotation activities upstream in the Meža River valley in the Republic of Slovenia and Austria (Šajn, et al., 2000 ; Souvent, 1994). The enrichment of soil with Hg and As is characteristic for land areas with intensive agricultural activities, but the Hg anomaly was also observed in the region of Varaždin as a consequence of city traffic and industry. The source rocks for the Drava River alluvial sediments are predominantly carbonate rocks (limestone, dolomite and marl) which results in the higher concentration of Ca and Mg in the soil. The increasing of concentrations of almost all measured elements was observed after the Mura and the Drava Rivers confluence. This could be a consequence of the influence of the Mura River alluvial sediments and/or of intensive agriculture in that part of the Podravina region. The soil developed on the Mura river alluvial sediments contains more Pb than in soils developed on the Drava River alluvial sediments before and after the Mura and the Drava Rivers confluence (Galović et al., 2002). Significantly higher contents of PHES and other heavy metals in soils are between Terezino Polje and Donji Miholjac. In this agricultural region the increasing of concentrations could be a consequence of fertilizers (Zn, Cu, Cr, Ni and Pb) (Adriano, 1986). The lowering of Hg and As contents is probably a consequence of decreased pesticide usage (Hg, As) (Adriano, 1986). The source rocks for soils developed on the Drava River alluvial sediments in the investigated area are carbonate bearing rocks which results in the constant increasing of the concentration of Ca and Mg in the soil downstream.

geochemistry; soil; alluvial sediments; Drava River; Sava River; Croatia

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