Serpentine soils from 16 sample points in Serbia as well as the roots and shoots of eight Brassicaceae family species: Aethionema saxatile, Alyssum montanum, Alyssum repens, Cardamine plumieri, Erysimum linariifolium, Erysimum carniolicum, Isatis tinctoria, Rorippa lippizensis, were analyzed with regard to their concentrations of P, K, Fe, Ca, Mg, Ni, Zn, Mn, Cu, Cr, Cd, and Pb. Most of the soil samples were typical of ultramafic sites with low concentrations of P, K and Ca and high concentrations of Mg, Fe, Ni and Zn. Ca/Mg ratio was <1 in most soil samples and Brassicaceae plants. Only in A. montanum, A. repens, E. linariifolium and R. lippizensis was the Ca/Mg ratio >1. The levels of P, K, Fe and Zn were high, Mn and Cu occurred in low amounts, whereas Cr, Cd, Co and Pb were only traceable. In the roots and shoots of A. montanum and A. repens the measured concentrations of Ni were 657 mg kg-1 and 676 mg kg-1 respectively, which is the first instance that such high concentrations of Ni were detected in these two species.
The numerical investigation of the mixing process in complex geometry micromixers, as a function of various inlet conditions and various micromixer vibrations, was performed. The examined devices were two-dimensional (2D) and three-dimensional (3D) types of serpentine micromixers with two inlets. Entering fluids were perturbed with a wide range of the frequency (0 - 50 Hz) of pulsations. Additionally, mixing fluids also entered in the same or opposite phase of pulsations. The performed numerical calculations were 3D to capture the proximity of all the walls, which has a substantial influence on microchannel flow. The geometry of the 3D type serpentine micromixer corresponded to the physically existing device, characterised by excellent mixing properties but also a challenging production process (Malecha et al., 2009). It was shown that low-frequency perturbations could improve the average mixing efficiency of the 2D micromixer by only about 2% and additionally led to a disadvantageously non-uniform mixture quality in time. It was also shown that high-frequency mixing could level these fluctuations and more significantly improve the mixing quality. In the second part of the paper a faster and simplified method of evaluation of mixing quality was introduced. This method was based on calculating the length of the contact interface between mixing fluids. It was used to evaluate the 2D type serpentine micromixer performance under various types of vibrations and under a wide range of vibration frequencies.
The aim of this study was to determine the ecological characteristics of vascular plants colonizing serpentine mining waste dumps and quarries in Lower Silesia. The investigated flora was analyzed with regard to species composition, geographical-historical status, life forms, as well as selected ecological factors, such as light and trophic preferences, soil moisture and reaction, value of resistance to increased heavy metals content in the soil, seed dispersal modes and occurrence of mycorrhiza. There were 113 species of vascular plants, belonging to 28 families, found on seven sites in the study. The most numerous families were Asteraceae, Poaceae, Fabaceae and Caryophyllaceae. Only 13% of all plants recorded occurred on at least five of the study sites. The most numerous were species related to dry grassland communities, particularly of the Festuco-Brometea class, which included taxa endangered in the region of Lower Silesia: Avenula pratensis, Salvia pratensis, Festuca valesiaca. Apophytes dominated in the flora of the investigated communities. Hemicryptophytes were the most numerous group and therophytes were also abundant. The serpentine mining waste dumps and querries hosted heliophilous species which prefer mesic or dry habitats moderately poor in nutrients, featuring neutral soil reaction. On two study sites 30% of the flora composition consisted of species that tolerate an increased content of heavy metals in the soil. Anemochoric species were the most numerous with regard to types of seed dispersal. Species with an arbuscular type of mycorrhiza were definitely dominant in the flora of all the study sites, however, the number of nonmycorrhizal species was also relatively high. It was suggested that both the specific characteristics of the habitats from serpentine mining and the vegetation of adjacent areas had a major impact on the flora composition of the communities in the investigated sites.
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