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Soil pollution screening using physico-chemical and cytogenetic approaches: a case study of a Bulgarian Suburban Nature Park

100%

Koleva V. , Dragoeva A. , Koynova T. , Natchev N.

Polish Journal of Environmental Studies

2018

tom 27

nr 3

Increasing attention has been paid recently to soil pollution. The aim of this study was to evaluate the ecological risk of soils collected from Nature Park Shumen Plateau (Bulgaria) (NP) using physicochemical and cytogenetic approaches (pH analysis, analysis of the content of heavy metals included in Bulgarian soil pollution standards, and Allium cepa-test). Soil samples from NP were collected from seven sites. A sample from a heavily anthropogenic-influenced urban site was also collected. As signs for environmental risk used pH values, we found total concentration of heavy metals and mitotic abnormalities in Allium cepa root meristems included in Bulgarian legislation. Only two samples from NP were found to be slightly acidic. The other samples have slightly alkaline pH. The highest pH value was obtained in the urban sample. Heavy metal concentrations did not exceeded national standards for soil pollution. Several NP samples and urban samples exerted cytotoxic and genotoxic effects in Allium root meristems. Our data on soil pH and heavy metal concentrations did not indicate potential ecological risk, but cytogenetic endpoints showed the presence of harmful compounds in studied areas. In conclusion, the ecological risk for the investigated suburban area may be assessed as moderate.

(13)C CP MAS NMR study of some 4,4'-disubstituted-trans-azobenzenes

100%

Maciejewska D. , Koleva V. , Wawer I.

Polish Journal of Chemistry

1998

tom Vol. 72, nr 12

2531-2536

Azobenzenes with para-dimethylamino group at aromatic ring and various para substitutes to another phenyl have been studied by (13)C CP MAS NMR spetroscopy followed by semi-empirical AMI MO calculations. The locked trans-configuration around N=N bond in the state results in non-equivalence of ortho carbons (C2 and C6, also C2' and C6') and the diference in chemical shifts is 12.9-22.0 ppm. The separation of meta carbons resonances is less manifested but in 1, 3, 4, 8 the non-equivalence of C3' and C5' is enhanced by the orientation of X-substituents at C4'.

Structure and Hydrogen Bonding of Solid N1-Alkyl-N2-(2-hydroxy, 4- or 5-methylphenyl)thioureas

100%

Wawer I. , Anulewicz-Ostrowska R. , Maciejewska D. , Koleva V.

Polish Journal of Chemistry

2000

tom Vol. 74, nr 6

823-835

Crystalline N1-alkyl-N2-arylthioureas with ortho hydroxyl and para or meta methyl substituents to the phenyl ring were studied by single crystal X-ray diffraction, IR and solid state 13C cP MAS NMR. Two different modes of association were found: i) intermolecular N1H...S bonds and N2H not involved in hydrogen bonding in N1-methyl-N2-(2-hydroxy, 5-metylphenyl)thuiourea 1, ii) cyclic dimers with two N2H...S hydrogen bonds (S...N2 distance of 3.332 A) and N1H engaged in intermolecular N1H...O bond in N1-methyl-N2-(2-hydroxy,4 methylphenyl)thiourea 2. Changes of carbon chemical shifts between solution and solid state result mainly from the reorientation of the aromatic ring with respect to the thiourea fragent.