engleski

Mercury contamination of soil, stream and overbank sediments associated with cinnabar mineralization (Trsce, Croatia)

There is a mono-mineral cinnabar deposit of no economic significance in the region around Trsce (Croatia). A geochemical survay was carried out over an area of 12 km2 in order to determine pollution in this picturesque region of Gorski kotar. According to a 400 m square grid, 40 topsoil samples were collected, as well as 21 samples of stream and 35 samples of overbank sediments. Concentrations of Hg were determined in all samples by CV AAS, and 14 elements in soil using ICP-OES after aqua-regia digestion. Average Hg content in soil was 2, 38 mg/kg, in the range from 0, 05 to 48 mg/kg. In stream sediments avarage Hg was 0, 67 mg/kg, in the range from 0, 05 to 3, 63 mg/kg. In the profile of the overbank sedoment Trsce 1, the avarage Hg content was 0, 20 mg/kg, and in profile Trsce 2 it was 0, 63 mg/kg. The age of mineral deposit is Middle Triassic, which belongs to the same metalogenetic province as Idrija (Slovenia). Soil samples were divided into two groups of Triassic and Permian age using geological map and GIS. After processing data of the Triassic group, Ba, Pb, S and Zn highly correlated with Hg. Correlation coefficients ranged from 0, 86 to 0, 93 (p < 0.05). Cluster analysis applied on the whole dataset identified three main groups. The first one comprises Hg, Ba, S, Pb and Zn, indicating influence of mineralization. The elements Co, Mn, Mg and Ni which form bonds with oxides and hydroxides of Fe and Mn contribute in the second group. The third group comprises siderophile elements Fe, Cu and Cr. Weathering of cinnabar and subsequent natural dispersion caused the increase of Hg content in soil, stream and overbank sediments. It was determined by GIS and spatial analysis that the area of 1, 101 km2 has been polluted by mercury.

cinnabar mineralization ; multivariate statistics ; spatial analysis

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