Hypericum perforatum L. and Achillea millefolium L. are plants which can be characterized as heavy metal accumulators. Including relating soils samples differing in pH reaction, 14 samples of St. John's wort and 9 samples of yarrow were collected from different localities in Yugoslavia and Republic Srpska. The total heavy metal content (Mn, Zn, Cu, Pb, Ni and Cd) was determined in the collected herb material (for St. John's wort-25 cm from the top of plant and for yarrow-30 cm) by standard analytical methods. Heavy metal content in the herb mostly dependent on soil composition, for both species. Concentration of Mn and Zn in the herb decreased linearly with the increase of soil pH (Mn: r =-0.62* for yarrow and r =-0.66* for St. John's wort; Zn: r =-0.71* for yarrow and r =-0.62* for St. John's wort), while Cd concentration decreased exponentially (r =-0.77* for yarrow and r =-0.58* for St. John's wort). Cd content in St. John's wort was mostly above limit of 0.5 ppm when soil pH (in nKCl) was lower than 5.9, and 4.5 for yarrow. Higher Cd content in the yarrow herb, and especially St. John's wort herb from acidic soils, points to significance of: 1. Required control of Cd content in the raw materials collected in the wild and 2. Necessary avoidance of such soils for cultivated production of those species. A relationship of Ni content in the herb with soil pH was found only for St. John's wort (r =-0.80***). Correlation between heavy metal content in the herb and humus content in the soil was analyzed but statistically significant regression coefficients were not obtained. Positive linear dependence was found between Pb and Ni content in the herb and their total content in the soil, for Achillea millefolium L. (r = 0.88** and r = 0.65*, respectively), which can be explained by the origin of the samples. Also, there is increase of Cu, Pb and Ni content in the yarrow herb with the increase of their available content in the soil (r = 0.67*, r = 0.88**, r = 0.65 *, respectively), while such dependence was obtained only for Pb content in St. John's wort herb (0.56*).

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Bentonite samples from Petrovac and Aleksinac were treated with sulfuric acid of different molarities. Differences in structure and texture of the initial and modified bentonite were determined by chemical analysis and Xraypowder diffraction (XRPD), infra-red spectroscopy (FTIR), scanning electron microscopy (SEM) and physisorption nitrogen at −196°C. Sulfuric acid caused an exchange of Al3+, Fe3+ and Mg2+ with H+ ions which led to a modification of the smectite crystalline structure. The Mg and Fe substitution in the octahedral sheet promoted the dispersion of those layers and forming of amorphous silicon. The sequence according to which the cations left the octahedral sheets was as follows: Mg2+>Fe3+>Al3+. The sulfuric acid activated bentonites exhibiting a lower cation exchange capacity (CEC) and а change of specific surface area (SBET) from 6 to 387 for bentonite from Petrovac and from 44 to 1784 m2 g-1 for bentonite from Aleksinac, positioning them as an excellent absorber in wine technology and in the protection of soil and environment

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Purpose Climate change is contributing to an increase in extreme weather events. This results in a higher river flooding risk, causing a series of environmental disturbances, including potential contamination of agricultural soil. In Serbia, the catastrophic floods of 2014 affected six river basins, including the Kolubara River Basin, as one of the larger sub-catchments of the large regional Sava River Basin, which is characterized by large areas under agricultural cultures, various geological substrates, and different types of industrial pollution. The main aim of this study was to establish the sources of potentially toxic elements in soil and flood sediments and the effect of the flood on their concentrations. Materials and methods Field sampling was performed immediately after water had receded from the flooded area in May 2014. In total, 36 soil samples and 28 flood sediment samples were collected. After acid digestion (HNO 3 ), concentrations of the most frequent potentially toxic elements (PTE) in agricultural production (As, Cd, Cr, Cu, Ni, Pb, Zn) and Co which are closely related to the geological characteristics of river catchments, were analyzed. The origin, source, and interrelations of microelements, as well as background values of the PTE of the river catchment, the pollution index (Pi), enrichment factor (Ef), and geological index (Igeo), were determined, using statistical methods such as Pearson correlations, principal component analysis (PCA), and multiple linear regression (MLRA). Results and discussionThe content of the hot acid-extractable forms of the elements, PCA, and MLRA revealed a heavy geological influence on microelement content, especially on Ni, Cr, and Co, while an anthropogenic influence was observed for Cu, Zn, and Cd content. This mixed impact was primarily related to mines and their impact on As and Pb content. The pseudo-total concentrations of all the analyzed elements did not prove to be a danger in the catchment area, except for Cu in some samples, indicating point-source pollution, and Ni, whose pseudo-total content could be a limiting factor in agricultural production. For the Ef, the Ni content in 59% soil and 68% flood sediment samples is classified into influence classes. Conclusions The similar pseudo-total contents of the elements studied in soil samples and flood sediment and their origin indicate that the long-term soil formation process is subject to periodic flooding in the Kolubara River Basin without any significant

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