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Zawartość wybranych metali ciężkich w powierzchniowych warstwach gleb terenów zieleni uniwersyteckiej

Druszcz P., Pater O., Stadnik M., Piwecka N., Cierpiński D., Kołek A, Malinowska A., Rybicka A., Bartyzel T., Kostecki J.

Quarterly of Environmental Engineering and Design

2018

Vol. 170 (50)

18--25

Świadomie kształtowane tereny zieleni powinny być nie tylko atrakcyjne wizualnie, lecz również bezpieczne dla użytkowników. W pracy przedstawiono analizę stanu zieleńców uniwersyteckich zlokalizowanych na campusie A Uniwersytetu Zielonogórskiego. Badania obejmowały właściwości fizyczno-chemiczne gleb, w tym analizę zawartości form ogólnych i biodostępnych wybranych metali ciężkich. Stwierdzono, że gleba na terenach zieleni wykazuje znaczne przekształcenia antropogeniczne, jednak zawartość metali ciężkich nie przekracza obowiązujących limitów.

The structure of the first co-ordination shell of Pb atoms in lead - silicate glasses : a molecular dynamics study

Rybicka A., Rybicki J., Witkowska A., Feliziani S., Mancini G.

Computational Methods in Science and Technology

1999

Vol. 5

67-74

The structure of lead-silicate glasses, although being investigated for over sixty years, rema ins still controversial. One of the open questions is the structure of the lead subsystem: what are the basic structural units like, and how are they interconnected. In the literature the appearance of [PbO4]n, or [PbO3]n chains is reported even in the glasses of the same stoichiometry. In order to elucidate the problem of contradicting experimental findings, extensive molecular dynamics (MD) simulations in the isobaric-isoenthalpic (NpH) ensemble of the structure of lead-silicate glasses have been performed in the whole range of glassformation. The atoms were assumed to interact by a two-body Born-Mayer-Huggins interaction potential with full ionic charges. The potential parametrization was taken from Damodaran et al. [Phys. Chem. Glasses, 31, 212 (1990)]. The simulation box contained about 3000 atoms. For each composition an equilibrated melt at 10000 K was prepared, and then slowly (6 ź 1013 K/s) cooled down to 300 K, passing several equilibrium states at intermediate temperatures. The simulation results can be summarised as follows. For 0.1 = x = 0.33, about ? of all Pb atoms is either placed in the front of the faces of the SiO 4 tetrahedra, forming PbO3 pyramids with the Pb atom in the vertices or in the middle of an almost flat triangle formed from apical oxygens of three different SiO 4 tetrahedra. Another ? of all Pb atoms can be qualified as vertices of rather distorted square pyramids. The remaining ? o f lead atoms have neighbourhoods difficult to classify. For x = 0.67 only a few Pb atoms were identified as remaining in the front of a face of a SiO 4 tetrahedron. Most of the Pb atoms are placed in the vertices of edge sharing square PbO4 pyramids. Our MD results are compared with available experimental data.