Ivanic M.,Ruder Boskovic Institute |
Vdovic N.,Ruder Boskovic Institute |
Barreto S.B.,Federal University of Pernambuco |
Bermanec V.,Horvatovac |
Sondi I.,Petrology and Mineral Resources
Geologia Croatica | Year: 2015
This paper comprises the research on the surface characteristics, the specific surface area (SSA), the cation exchange capacity (CEC) and the electrophoretic mobility (EPM) of the kaolin clays obtained from different naturally occurring pegmatite and granite deposits worldwide. Particularly the influence of the ancillary minerals on these properties was studied, as well as the diversity in morphological and structural characteristics of kaolinite in samples. The mineral composition and the morphology of the kaolin samples were investigated using X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM), respectively. The SSA was determined by BET method, the CEC by ammonium selective electrode and the surface charge by EPM measurements. The results showed that the surface properties of the kaolin samples were strongly influenced by the presence of ancillary constituents, particularly smectite minerals. Their occurrence, even in trace amounts, significantly increased SSA and CEC values of the investigated samples. Most importantly, EPM measurements revealed that the character of the amphoteric surfaces of the dominant kaolinite mineral in samples was rescinded by the permanent pH-independent siloxane basal charge of smectite. The presence of ancillary smectites, characterized with the higher surface reactivity, hindered the surface properties of the prevailing kaolinite mineral in the kaolin clay deposits. © 2015, Institute of Geology. All rights reserved.
Medunic G.,Horvatovac |
Smit Z.,Zagreb Public Health Institute
Rudarsko Geolosko Naftni Zbornik | Year: 2015
The aim of this study was to determine the presence and nature of organic micropollutants in river overbank and floodplain sediments from the border between Croatia and Bosnia and Herzegovina following the catastrophic 2014 flood. The study involved ten sediment samples from the Sava and Bosna river floodplain. The volatile aromatic compounds, i.e. benzene, toluene, ethylbenzene, and xylene (BTEX), together with alkanes (the linear straight-chain alkanes and the branched alkanes, C10-C28) were determined by GC-MS method. Their estimated amounts were from <0.054 to 3.886 mg/kg, and from 10 to 406 mg/kg, respectively. Hereby, they were below allowed concentration limits for total hydrocarbons in agricultural soil of lighter texture (sandy/loam soil) which is 1000 mg/kg, whilst for heavier clayey soils the limit is 2000 mg/kg. However, their presence in itself in the investigated sediment indicates oil spill problems, whilst their possible sources might be local oil refining industries located in the local cities of Brod and Modriča in Bosnia and Herzegovina. © The Author(s).
Mezga A.,Horvatovac |
Cvetko Tesovic B.,Horvatovac |
Pretkovic V.,Horvatovac |
Jovanovic N.,Horvatovac |
Geologia Croatica | Year: 2015
Sixteen dinosaur footprints are exposed along the upper-bedding plane of a single Upper Hauterivian limestone layer in the Palud bay (western Istria, Croatia). This distinct footprint-bearing horizon is part of the thick Mesozoic Adriatic-Dinaridic Carbonate Platform stratal succession. Strata at the Palud site are characterized by peritidal (shallow subtidal to intertidal) limestone with several shallowing-upward cycles composed of mudstone, peloidal wackestone/packstone, peloidal packstone/grainstone and fenestral mudstone/wackestone with common geopetal infill. The Late Hauterivian age of these deposits is determined from their microfossil assemblage, which is dominated by ostracods, benthic foraminifera and calcareous green algae Dasycladales. The Palud site dinosaur footprints are circular to elliptical in shape, with no clearly visible digit impressions (except for one questionable example), and are rather large with average length of 30 cm. Most footprints have a well-defined expulsion rim that represents displacement and compression of soft, waterlogged sediment substrate by the weight of the dinosaur. All of the footprints are of nearly same shape and size, which indicates that they were produced by the same kind of tracemaker – likely a sauropod dinosaur. These animals left their footprints on top of a shallowing-upward succession of an intertidal environment during a short subaerial exposure of fine-grained carbonate sediment. © 2015, Institute of Geology. All rights reserved.