engleski

Selected element concentrations in alluvial sediments under garbage disposal site (Zagreb, Croatia)

Ag, Ba, Cd, Ce, Cs, Co, Cr, Cu, Eu, Fe, Ga, Mn, Ni, Pb, Rb, Sb, Sc, Sr, Th, Ti, V, Zn, and Zr concentrations in alluvial sediments were determined by INAA and OES in the area used as the garbage disposal site in the vicinity of water-well field. Results show that total concentrations of analysed elements depend on sediment characteristics: mineral composition, specific surface area, CEC, organic matter and clay-grain size fraction content. On the other hand, concentrations in sediment depend on physico-chemical forms and geochemical characteristics of elements in question. Most of the elements reveal excellent/very good correlations with iron, while strontium shows negative correlation with iron. Strontium has very good positive correlation with carbonate content, while all other analysed elements, except silver, have excellent negative correlations with carbonates. Correlations with clay-grain size fraction are good or very good for all elements, except strontium and silver. The only element which is not correlated, neither with iron, carbonate, nor with clay-grain size fraction is silver. One can conclude therefore, that silver is introduced as discrete particles. Extremely high silver concentration was found at 6.5-6.8 meters below garbage in the aerated layer occasionally under the water table. Enrichment factor for silver is found to be 127, which is the clear indication of sediment pollution with silver. Long-lasting clandestine deposition of industrial wastes on disposal site meant for domestic wastes might be the reason. The elevated concentrations found on the 11.2-11.4 m depth are concordant with mineralogical composition (MnO-hydroxides, iron minerals, illite, chlorite) and enrichment factors for majority of analysed elements are below 2. For the time being, this sediment layer acts as chemical filter preventing the infiltration from vertical direction. Concentrations and enrichment factors of all determined elements from the uppermost and deeper water bearing layers are of natural values. Taking into account these and additional piezometer results, it can be concluded that the quality of water exploited from the water-well field downstream garbage disposal site is not endangered so far.

INAA; OES; alluvial sediments; trace elements; garbage disposal site; Ag; enrichment factor; correlations

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